JP2012027005A - Near-field optical microscope, and sample observation method - Google Patents

Abstract

Provided is a scanning near-field optical microscope capable of high-resolution observation without directly contacting a sample with a microstructure that generates or selectively transmits near-field light.
A scanning near-field optical microscope 100 according to the present invention includes a light irradiation unit 102 for emitting illumination light to a sample 107, a light receiving unit 112 for receiving light, an emission side of the light irradiation unit 102, and It is arranged on at least one of the incident sides of the light-receiving unit 112, and has a fine structure that generates or selectively transmits near-field light, and has an anisotropy in dielectric constant or magnetic permeability and transmits near-field light. A high wavenumber transmission medium 106.
[Selection] Figure 1

Description

  The present invention relates to a near-field optical microscope and a sample observation method using the same.

  When a fine structure is observed by optical means, the resolution obtained has an upper limit (diffraction limit) determined by the wavelength of light and the numerical aperture of the optical system. However, in recent years, techniques for observing extremely minute structures have been demanded, and research on optical means for improving the resolution beyond the diffraction limit has been actively conducted.

  An optical means using a negative refractive index, a negative dielectric constant, or a negative magnetic permeability medium as a lens has been proposed (for example, see Non-Patent Document 1). Such a lens is generally called a super lens. According to such a technique, imaging with extremely high resolution exceeding the diffraction limit is possible. In addition, a technology has been proposed that uses a medium (anisotropic medium) with an effective permittivity sign that varies depending on the direction, formed by alternately laminating metal and dielectric materials, to achieve an effect similar to that of a super lens. (For example, see Non-Patent Document 2).

  By the way, whether it is a super lens or an anisotropic medium as described above, the obtained image contains high spatial frequency information that becomes an evanescent wave in a vacuum. Cannot be observed. In order to detect such information with a high spatial frequency without losing information, for example, a technique of forming a multilayer film in a curved shape (for example, see Non-Patent Document 2) or the like, or a near-field optical microscope is used. It is necessary to use it (for example, refer patent document 1). Furthermore, a configuration for detecting an image formed by a super lens using a near-field optical microscope has been proposed (see, for example, Non-Patent Document 3).

  Near-field optical microscopes can be roughly classified into illumination types, scattering types, and condensing types depending on the element configuration for converting near-field light into propagating light (see, for example, Patent Document 2). Here, the scattering near-field optical microscope 900 will be described in detail with reference to FIG.

  FIG. 30 is a schematic diagram showing a system configuration of a near-field optical microscope according to the prior art. As shown in FIG. 30, the illumination light emitted from the light source 902 is converted into substantially parallel light (plane wave) by the collimator lens 906, and then collected on the sample 901 by the objective lens 903 via the first half mirror 907. Lighted. A part of the collected light is scattered by the probe 904 in a state of carrying optical information in the vicinity of the surface of the sample 901. The sample 901 is placed on a sample table 914 controlled by a computer 921, a sample controller 915, and a sample actuator 916, and the probe 904 is sampled by the computer 921, the controller 919, and the probe actuator 934. The desired upper position is controlled so as to be observable. The detector 932 detects the deflection of the probe 904 due to the atomic force acting between the sample 901 and the probe 904, and makes the distance between the tip of the probe 904 and the surface of the sample 901 constant by AFM (Atomic Force Microscope) control. keep.

  Part of the light scattered by the probe 904 is detected by the photomultiplier tube 931 through the condenser lens 928, the detection imaging lens 929, and the pinhole 930. At this time, light from a place other than the tip of the probe 904 is blocked by the pinhole 930, so that the light scattered at the tip of the probe 904 can be detected with a high S / N ratio. Alternatively, the S / N ratio can be further increased by applying time modulation to the irradiation light and detecting the lock-in of the output signal. The output signal from the photomultiplier tube 931 is amplified by a preamplifier 933 such as a lock-in amplifier, and image processing is performed by the computer 921 using the amplified signal.

  On the other hand, the light reflected by the sample 901 out of the light condensed on the sample 901 is incident on the objective lens 903 again, reflected by the first half mirror 907, and enters the observation optical system S1. Further, the image is divided into two by the second half mirror 908, one imaged on the image sensor 910 by the imaging lens 909, and the other image can be visually observed by the eyepiece lens 911.

  In general, the resolving power of optical observation by a probe is generally determined by the larger of the dimension of the probe tip and the distance from the probe tip to the sample. In order to obtain a significantly higher resolution than that of an optical microscope, when using visible light, it is necessary to keep the distance between the probe tip and the sample approximately 100 nm or less. As described above, the near-field optical microscope requires nanometer-scale control of the distance between the probe tip and the sample.

JP 2006-138633 A JP 2002-340771 A

J. B. Pendry, Physical Review Letters Vol.85, p.3966-3969 (2000) A. Salandrino et al., Physical Review B Vol.74, 075103 (2006) T. Taubner et al., Science Vol.313, p.1595 (2006)

  However, the probe tip has a complex nanostructure. For example, when it is used for a wet sample such as a cell, the microstructure that generates or selectively transmits near-field light such as the probe tip is In contact with the sample due to the unevenness of the sample or the vibration of the device, contamination and damage due to proteins, etc. occur, resulting in deterioration of light transmission, deterioration of light localization, etc., which hinders observation at high resolution It was.

  Accordingly, an object of the present invention is to provide a scanning near-field optical microscope capable of high-resolution observation without directly contacting a sample with a microstructure that generates or selectively transmits near-field light.

The near-field optical microscope according to the present invention that achieves the above object is as follows.
A light irradiation unit for emitting illumination light to the sample;
A light receiving portion for receiving light;
A microstructure that is disposed on at least one of the emission side of the light irradiating unit and the incident side of the light receiving unit, and that generates or selectively transmits near-field light; and
An ultrahigh wavenumber transmission medium that exhibits anisotropy in dielectric constant or magnetic permeability and transmits near-field light;
It is characterized by providing.

Furthermore, the sample observation method according to the present invention that achieves the above object is as follows.
A dielectric constant or a magnetic permeability showing anisotropy, and a step of closely adhering an ultrahigh wavenumber transmission medium that transmits near-field light to a sample;
Irradiating the sample with light;
Receiving light emitted from the ultrahigh wave number transmission medium in close contact with the sample through a fine structure.

  According to the scanning near-field optical microscope of the present invention, optical information having a spatial frequency higher than the spatial frequency corresponding to the wavelength of the irradiation light can be obtained with high sensitivity.

It is the schematic which shows an example of the system configuration | structure of the near-field optical microscope according to 1st Embodiment of this invention. It is an enlarged view which shows the opening part which comprises the fine structure of the near-field optical microscope shown in FIG. 1, and its periphery. It is an enlarged view which shows the opening part which comprises the fine structure of the near-field optical microscope shown in FIG. 1, and its periphery. It is a figure which shows the structure of the near-field light source by which the light source and the light-shielding member provided with the opening part were comprised integrally. It is a figure which shows the structure of the near-field light source which provided the opening part directly in the light source. It is a schematic diagram for demonstrating the scanning part of the near-field optical microscope shown in FIG. It is the schematic which shows an example of schematic structure of the near field excitation unit of the near field optical microscope shown in FIG. It is a schematic diagram for demonstrating the role of the objective lens in the near-field optical microscope shown in FIG. It is a schematic diagram which shows an example of a structure of the near field excitation unit provided with the transmission illumination for optical microscope observation. It is a schematic diagram which shows the other example of a structure of the near-field excitation unit provided with the transmission illumination for optical microscope observation. It is a schematic diagram which shows the near-field excitation unit which has a process surface which performed the process for improving adhesiveness with a sample. It is a graph which shows the performance of an ultrahigh wave number transmission medium, a near field light source, and an objective lens with respect to the frequency of illumination light. It is a schematic diagram for demonstrating the near-field optical microscope which concerns on 1st Embodiment which enabled rotation of the near-field light source. It is the schematic which shows an example of schematic structure of a near-field light source provided with a polarization conversion means. It is a schematic diagram which shows the principal part of a near-field optical microscope provided with two near-field light sources. It is a schematic diagram which shows the principal part of a near-field optical microscope provided with two opening parts. It is a schematic diagram which shows the structure which integrated the fine structure and the ultrahigh wavenumber transmission medium. It is the schematic which shows the system configuration | structure of the near-field optical microscope according to 2nd Embodiment. It is a schematic diagram which shows the operation | movement of an objective lens and an optical probe unit of the near-field optical microscope according to 2nd Embodiment, (a) shows a general view, (b) shows the enlarged view around an opening part. . It is a schematic diagram which shows arrangement | positioning of the optical probe unit and a sample of the near-field optical microscope according to 2nd Embodiment, (a) is pressing an optical probe unit against a sample, (b) is pressing an optical probe unit against a sample. Shown after applying. It is a schematic diagram which shows the structure for performing the illumination for optical microscopes of the near-field optical microscope according to this invention. It is a schematic diagram which shows another structure for performing the illumination for optical microscopes of the near-field optical microscope which concerns on 2nd Embodiment. It is a schematic diagram which shows the optical probe unit which improved the adhesiveness with the sample surface of the near-field optical microscope which concerns on 2nd Embodiment. It is the graph which showed the performance of the near field optical probe, the ultrahigh wavenumber transmission medium, and the objective lens with respect to the frequency of illumination light. It is the schematic which shows the other system configuration | structure of the near-field optical microscope according to 2nd Embodiment. It is a figure which shows the equal frequency curve of an anisotropic medium. It is a conceptual diagram of the structure which shows an example of the artificial structure which gives an anisotropy to an effective dielectric constant. It is a figure which shows an example of the component of the effective dielectric constant of the metal dielectric multilayer film shown in FIG. It is a conceptual diagram which shows the other example of the artificial structure which gives an anisotropy to an effective dielectric constant. It is the schematic which shows the system configuration | structure of the conventional near field optical microscope.

  Embodiments of an inspection apparatus according to the present invention will be described below in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows an example of the system configuration of a near-field optical microscope according to the first embodiment of the present invention. The near-field optical microscope 100 includes a scanning unit 101, a near-field light source 105, an ultrahigh wavenumber transmission medium 106, a light receiving unit 112, a half mirror 113, an imaging lens 114, an image sensor 115, and an optical microscope. An illumination unit (hereinafter referred to as an optical microscope illumination unit) 116. The ultra high wave number transmission medium 106 is disposed between the sample 107 and the opening 104. In addition, the ultrahigh wave number transmission medium 106 is disposed so as to be in contact with the sample 107. The light receiving unit 112 includes an objective lens 108, a dichroic mirror 109, a filter 110, and a light receiving element 111.

  Light (wavelength Eλ) emitted from the light source 102 that constitutes a light irradiation unit for emitting illumination light to the sample 107 is irradiated to the light shielding member 103. Since the light shielding member 103 is provided with an opening 104 smaller than the wavelength of light, the light that has passed through the opening 104 oozes out to the back side of the light shielding member 103 as near-field light. That is, the opening 104 constituted by a fine structure is arranged on the emission side of the light source 102 constituting the light irradiation unit, and generates near-field light. Hereinafter, this near-field light is referred to as illumination light. An ultrahigh wavenumber transmission medium 106 is disposed below the light shielding member 103 with an interval smaller than the wavelength, and a part of the illumination light enters the ultrahigh wavenumber transmission medium 106.

  The ultra-high wave number transmission medium 106 has an anisotropy in permittivity or permeability and transmits near-field light. The optical performance of the ultra high wave number transmission medium will be described later. The ultrahigh wavenumber transmission medium 106 can also transmit illumination light, which becomes near-field light in the air, as a propagation light, and the ultrahigh wavenumber transmission medium 106 and the sample 107 are in contact with each other. A part of the light emitted from the laser beam reaches the sample 107. That is, the ultra-high wave number transmission medium 106 transmits near-field light generated at the opening 104 constituting the fine structure and emits it to the sample 107 as illumination light. Therefore, the opening 104 does not contact the sample 107 directly. Although the ultrahigh wavenumber transmission medium 106 is arranged so as to be in contact with the sample 107, the sample 107 may be arranged at a distance where the near-field light emitted from the ultrahigh wavenumber transmission medium 106 is not attenuated. . In addition, when the ultrahigh wavenumber transmission medium 106 is pressed against the sample 107 and arranged so as to be in contact with each other, the ultrahigh wavenumber transmission medium 106 is used even if the sample has an unstable shape such as a living cell. Since the distance between the sample 107 and the sample 107 can be narrowed, high-definition observation can be performed stably with high resolution.

  Here, it is assumed that a fluorescent dye that emits fluorescence of wavelength Fλ is diffused in sample 107 when excited by light of wavelength Eλ. The fluorescent dye in the sample 107 is excited by light irradiated from the light source 102 through the opening 104 and the ultrahigh wave number transmission medium. The fluorescent dye may be diffused directly into the sample 107 or may be contained in the sample 107 in a processed state like a fluorescent bead. Alternatively, a fluorescent protein such as GFP (Green Fluorescent Protein) may be bound to the sample 107 so that a specific part or function in the sample 107 can be observed. Part of the fluorescence having the wavelength Fλ emitted from the fluorescent dye passes through the objective lens 108, is reflected by the dichroic mirror 109, and enters the filter 110.

  In general, when fluorescence is generated using a fluorescent dye or quantum dots, the intensity of fluorescence is very weak with respect to excitation light. Therefore, also in the system configuration shown in FIG. 1, not only fluorescence but also excitation light having a higher intensity is incident on the objective lens 108. However, since the filter 110 is designed to remove excitation light and transmit fluorescence, only the fluorescence is detected by the light receiving element 111. Hereinafter, light including information (signal) related to the sample 107, such as fluorescence and excitation light or transmitted light transmitted through the sample, is referred to as signal light. The light receiving unit 112 receives light (signal light) from the sample 107.

  Since the illumination light carried to the sample 107 by the ultrahigh wave number transmission medium 106 is near-field light in the air or in the sample, it spreads only in the vicinity of the point incident on the sample 107 and does not propagate further. . In other words, even if the fluorescent dye is evenly diffused in the sample 107, only the fluorescent dye in the vicinity of the point where the near-field light is incident is excited, so that the light receiving unit 112 is a local region in a region smaller than the wavelength of the illumination light. Only specific information (in this case, the spatial distribution of the fluorescent dye) is detected. Therefore, if the signal light detection process as described above is continued for a predetermined time, it is possible to examine how the phenomenon occurring in the minute region of the sample surface layer changes with time.

  In particular, there is no example of such a local observation method for a soft and unstable sample such as a living cell, and such observation is possible by using the near-field optical microscope 100 according to the present embodiment. Become. The response light radiated from the sample 107 is light reflected, scattered, or diffracted by the sample 107, or fluorescence emitted from the fluorescent dye in the sample 107 when excited by illumination light. It holds information on optical properties such as distribution, light scattering coefficient distribution, diffraction efficiency distribution, and biochemical information such as spatial distribution of fluorescent dyes. Hereinafter, information on optical properties and biochemical information detectable by optical means are collectively referred to as “optical information”.

  Next, a method for obtaining a two-dimensional image of the surface of the sample 107 will be described with reference to FIG. The light source 102, the light shielding member 103, and the opening 104 provided in the light shielding member 103 may be configured as one body, and this will be referred to as a near-field light source 105. The near-field light source 105 constitutes a light irradiator for emitting illumination light to the sample. The opening 104 has a fine structure that generates near-field light. The scanning unit 101 includes, for example, a micro electro mechanical systems (MEMS) scanner driven by a motor or an electric stage using a piezo element. The scanning unit 101 includes a near-field light source 105 along the surface of the ultrahigh wavenumber transmission medium 106. The position can be changed continuously.

  At this time, since the position of the surface of the sample irradiated with the illumination light also changes, the time change of the light amount of the signal light detected by the light receiving element 111 corresponds to the position on the surface of the sample 107, whereby the surface of the sample 107 The fluorescent dye distribution can be obtained. When the near field optical microscope according to the present embodiment operates, the scanning unit 101 keeps the distance between the opening 104 forming the fine structure and the ultrahigh wavenumber transmission medium 106 equal to or less than the wavelength of the illumination light. Thereby, not only the resolving power at each of the plurality of observation positions is made constant, but also the optical information can be accurately detected by the light receiving unit 112.

  In the case where the light source 102 and the opening 104 are configured as independent elements, they may be moved together, but only the opening 104 may be moved. This is because the light emitted from the light source 102 and applied to the opening 104 is restricted by the diffraction limit, and thus spreads over at least the wavelength region. Therefore, even if the opening 104 is slightly moved in the large region, the intensity of near-field light (illumination light) that oozes out from the opening 104 hardly changes.

  The operation of the near-field optical microscope 100 has been described above by taking fluorescence observation as an example, but the same function is expected for other optical processes. For example, when the surface of the sample 107 has irregularities, or when the sample 107 has fluctuations in density or composition, the illumination light is scattered on the surface of the sample 107. When the scattering generated at this time is scattering accompanied by a change in optical frequency such as Raman scattering, the illumination light and the scattered light can be separated by the filter 110 in the same manner as in the previous fluorescence. On the other hand, in the case of elastic scattering such as Rayleigh scattering or Mie scattering, such an effect of the filter 110 cannot be expected. However, since the intensity of the elastically scattered light is extremely higher than that of fluorescence or Raman scattering, the illumination light detected together with the signal light can be treated as an acceptable level of noise light.

  On the other hand, the irradiation light emitted from the light microscope illumination unit 116 is irradiated onto the observation region on the sample 107 by the objective lens 108 through the half mirror 113 and the dichroic mirror 109. Then, light that has acted on the sample 107 is emitted from the sample 107. A part of this light again enters the objective lens 108, and light of a specific wavelength is reflected by the dichroic mirror 109 and is received by the light receiving element 111 through the filter 110. The light transmitted through the dichroic mirror 109 is reflected by the half mirror 113 and imaged on the image sensor 115 by the imaging lens 114. Although not shown, the output of the image sensor 115 is subjected to image processing by an image processing circuit (not shown) and supplied to a monitor or the like. Thereby, the state of the sample 107 can be observed in real time. Such an optical observation method is the same operation as a conventional optical microscope with epi-illumination. In the case where the sample 107 has transparency, an illuminating means for transmitting and illuminating the sample 107 can be disposed on the opposite side of the optical microscope through the sample 107.

  FIG. 2 is an enlarged view showing the opening 104 constituting the fine structure according to the present embodiment and its periphery. The light shielding member 103 is provided with an opening 104 having a size d. The shape of the opening 104 may be any shape such as a cylinder, a cube, or a rectangular parallelepiped. The size d represents the largest length when the opening 104 is viewed from the light source side, such as a diameter in the case of a cylinder and a diagonal of a square forming the same in the case of a cube. d is set to be smaller than the wavelength Eλ of the light emitted from the light source 102, so that the energy efficiency when the light emitted from the light source 102 passes through the opening 104 is not high. Nevertheless, a slight amount of light oozes out to the back side of the light shielding member 103 as near-field light and becomes illumination light.

  The near-field light includes a propagating light component that can propagate in the air and an evanescent wave component that exponentially attenuates in the air. The smaller the aperture size d is, the smaller the evanescent wave is. The ratio of components increases. The evanescent wave component attenuates exponentially as the distance from the light shielding member 103 increases. However, if the distance g between the light shielding member 103 and the ultrahigh wavenumber transmission medium 106 is smaller than the wavelength Eλ, a certain level of intensity is applied to the ultrahigh wavenumber transmission medium 106. To reach. Therefore, in order for the near-field optical microscope 100 of the present embodiment to operate satisfactorily, the size d of the opening 104 and the distance g between the light shielding member 103 and the ultrahigh wavenumber transmission medium 106 are both determined by the illumination light. Must be smaller than the wavelength Eλ.

  As a fine structure for generating near-field light, in addition to the opening 104, a scattering probe, a bullseye structure, a C-type opening, or the like may be used. The scattering probe is a probe having a pointed tip, and near-field light is generated when the tip is irradiated with light. Different types of methods such as an irradiation mode, a condensing mode, and a scattering mode have been proposed for the conventional near-field optical microscope. Among these, the irradiation mode and the scattering mode are the near-field in the near-field optical microscope 100 according to the present embodiment. It can be used as a means for generating light. The bullseye structure is a fine structure in which concentric grooves are formed around the opening 104 to strongly excite surface plasmons and generate strong near-field light on the side opposite to the illuminated surface. A C-shaped opening provides a similar effect.

  As the size d of the opening 104 is smaller, the resolution as a microscope can be increased. However, since most of the light emitted from the light source 102 is discarded, the obtained image becomes dark. On the other hand, the smaller the gap g, the more advantageous in both resolution and brightness. FIG. 3 is also an enlarged view showing the opening 104 and its periphery, but shows a configuration in which the gap g is zero, that is, the light-shielding member 103 is disposed so as to contact the ultrahigh-frequency transmission medium 106. Yes. As described above, it can be said that it is the best conceivable configuration when it comes to the influence of the gap g on the optical performance.

  However, in practice, no matter how flat the ultrahigh wavenumber transmission medium 106 and the light shielding member 103 are formed, it is impossible to avoid slight irregularities on the surface, and the opening 104 is completely located with respect to the ultrahigh wavenumber transmission medium 106. It is difficult to keep in contact with Therefore, it is preferable to operate the light shielding member 103 against the ultrahigh wavenumber transmission medium 106 in order to reduce the gap g inevitably generated due to the slight unevenness or dust contamination. Alternatively, if the light shielding member 103 having an opening is formed integrally with the ultrahigh wavenumber transmission medium 106, the interval g can be always strictly zero, and the above problem can be completely overcome. When it is necessary to obtain such a configuration and obtain a two-dimensional image, it is now possible to scan not the aperture 104 or the near-field light source 105 but the ultrahigh wavenumber transmission medium 106 itself with respect to the sample. Good.

  FIG. 4 is a diagram showing a structure of the near-field light source 102 in which the light source 102 and the light shielding member 103 having the opening 104 are integrally formed. Since the near-field optical microscope 100 is a device for observing a fine structure on the sample 107, if the positional relationship between the light source 102 and the opening 104 varies due to vibration or convection during operation, the near-field optical microscope 100 can be moved beyond the opening 104. The intensity and spatial distribution of near-field light that oozes out toward the high wavenumber transmission medium may change, and the optical performance of the resulting image may be significantly degraded.

  However, if the configuration of the near-field light source shown in FIG. 4 is adopted, since the light source 102 and the light shielding member 103 are fixed to the common casing 117, such a performance degradation is suppressed and good observation is performed. Can do. In order to use light energy from the light source 102 more efficiently, a condensing lens (not shown) is provided between the light source 102 and the light shielding member 103 to collect light and irradiate the opening 104. Is effective. In such a configuration, since the light is condensed in a narrow area near the opening 104, the minute opening 104 is continuously placed at the center of the area (the position where the light intensity is maximum). Requires advanced position control. In addition, when the position of the opening 104 fluctuates due to vibration or the like, the intensity of the illumination light that oozes out from the opening 104 changes greatly. That is, when a condensing lens (not shown) is provided in order to increase energy efficiency, the superiority of integrating the light source 102 and the light shielding member 103 into a near-field light source is further enhanced.

  Needless to say, the opening 104 may be provided directly in the light source 102 as shown in FIG. As the light source 102, various types of light sources such as a light emitting diode (LED), a laser diode (LD), a halogen lamp, a xenon lamp, and a mercury lamp can be used. In these light sources, if a region that emits light is called an emission part, the light shielding member 103 is provided so as to cover the emission part 118, and an opening 104 having a wavelength smaller than that is formed in a part thereof. When the near-field light source 105 is configured in this way, the positional relationship between the emission unit 118 and the opening 104 does not change regardless of any external environmental change such as vibration or thermal expansion, and stable near-field light can be obtained. Can be generated.

  FIG. 6 is a schematic diagram for explaining the scanning unit 101. The near-field light source is coupled to the scanning unit 101 via the coupling surface 119, and can move in one or two axial directions along the coupling surface 119 when an electric signal is given. As described above, the illumination light is irradiated to the sample (not shown) while the near-field light source 105 moves, and the signal light scattered by the sample or the signal light emitted from the fluorescent dye by exciting the fluorescent dye in the sample (fluorescence). ) Is detected by the light receiving unit 112, one-dimensional or two-dimensional spatial information of the sample surface can be obtained. In order to facilitate the movement of the near-field light source 105, lubricating oil may be filled between the near-field light source 105 and the ultrahigh wavenumber transmission medium 106, or beads may be diffused.

  Alternatively, the distance between the near-field light source 105 and the ultrahigh-frequency transmission medium 106 is kept constant by the action of hydrodynamic force, such as a flying head used in a hard disk drive (HDD) of a personal computer. Scanning can also be performed. Further, as shown in FIG. 7, the scanning unit 101, the near-field light source 105, and the ultrahigh wavenumber transmission medium 106 are fixed to or included in a common casing 117, and the near-field excitation unit 120 is integrally configured. May be. When such a configuration is used, the mechanical accuracy between the near-field light source 105 and the ultrahigh-frequency transmission medium 106 or the sample (not shown) is improved, and the influence of noise light leaking from the outside is reduced. From the viewpoint of optical performance.

  FIG. 8 is a schematic diagram for explaining the role of the objective lens 108 in the near-field optical microscope 100 according to the present embodiment. As already described, the objective lens 108 is a part constituting the light receiving unit 112 and plays a role of collecting more signal light emitted from the sample surface layer. On the other hand, as shown in FIG. 1, it is also possible to arrange the near-field optical microscope 100 on the optical microscope and share the objective lens 108. That is, as shown in FIG. 8, the sample 107 is disposed on the objective lens 108 of the optical microscope via the slide glass 121, and the ultrahigh wave number transmission medium 106 and the near-field light source 105 are provided on the sample surface 107a. When observing live cells, cells cultured in a petri dish or glass bottom dish are often used. In this case, the portion of the slide glass 121 in the figure is the bottom of the petri dish (glass bottom dish).

  FIG. 8 shows the optical axis OA and the field-of-view range FOV of the objective lens 108. In this way, at least a part of the aperture 104 and the ultrahigh-wavenumber transmission medium 106 is within the field-of-view range FOV of the optical microscope. In this configuration, both the optical microscope and the observation image of the sample obtained by the near-field optical microscope 100 can be obtained by observing the sample 107 within the visual field range FOV with the near-field optical microscope 100. In particular, when the region (field of view) that can be observed by the near-field optical microscope 100 is narrow, by using the optical microscope image as a viewfinder, the observation region can be specified and moved smoothly, and the operability is improved. . Microscopic observation using the optical microscope and the near-field optical microscope 100 uses light sources having different wavelengths in order to separate and detect both observation images (when using fluorescence, both excitation light and fluorescence have different wavelengths). Is preferred. However, when it is desired to use a light source having the same wavelength due to the nature of the sample, both of them can be observed in a time-sharing manner.

  FIG. 9 is a schematic diagram showing the near-field excitation unit 122 provided with transmission illumination for optical microscope observation. When observing a (semi) transparent sample such as a living cell, transmitted illumination is often used in order to use phase difference and differential interference. Therefore, in the near-field excitation unit 122, the light source element 123 for transmitting illumination is moved to the scanner movable portion 126 that is movable with respect to the scanner fixed portion 125 (that is, on the side opposite to the optical microscope described above with respect to the sample 107). The structure which performs the transmitted illumination of an optical microscope by further providing the comprised illumination part for optical microscopes is shown. Although the operation as the near-field optical microscope will not be described again, if the light source 102, the light shielding member 103, the opening 104, and the ultrahigh wavenumber transmission medium 106 are provided, necessary functions are exhibited.

  On the other hand, the transmitted illumination light emitted from the light emitting element 123 is applied to the sample surface 107 a through the transmission region 124 and the ultrahigh wavenumber transmission medium 106. The transmission region 124 is provided on the surface on the side facing the ultrahigh wavenumber transmission medium 106, and transmits the illumination light (transmission illumination light) from the light microscope illumination unit. The transmission region 124 and the ultrahigh wavenumber transmission medium 106 only need to be transparent or have a structure capable of guiding light only with respect to the wavelength of the transmitted illumination light. As shown in FIG. 9, the light source 102 used as the near-field light source and the light microscope illumination unit including the light emitting element 123 used for transmission illumination for the microscope can be provided on the same plane. In this case, the light source 102 and the light emitting element 123 can be formed over the same substrate by a semiconductor process, and productivity can be improved.

  In addition, as shown in FIG. 10, if the region operating as the near-field light source and the transmitted illumination region are separated by the light shielding member 103, the illumination light for the near-field optical microscope 100 is used as the optical microscope. Therefore, it is possible to suppress the deterioration of optical performance due to mixing of transmitted illumination light. Further, the light shielding member 103 can be used as a reflection surface for more effectively performing the transmitted illumination. 9 and 10, the light microscope illumination unit is provided in the scanner movable unit, but the light microscope illumination unit may be provided in the scanner fixing unit. Although not shown, a shielding part can be provided between the light source 102 and the light emitting element 123 constituting the light microscope illumination part in order to shield the illumination light from the light emitting element 123. Thereby, the illumination light from the light emitting element 123 and the illumination light from the light source 102 can be separated to reduce noise during observation, and as a result, an image with a good S / N ratio can be acquired.

  FIG. 11 is a schematic diagram showing a near-field excitation unit 122 having a treated surface on the sample-side surface of the ultrahigh wavenumber transmission medium 106 that has been subjected to a treatment for improving the adhesion to the sample 107. The near-field optical microscope 100 according to the present embodiment can obtain higher resolution than a conventional optical microscope by irradiating illumination light onto a very small region of the surface of the sample 107. Therefore, if the relative position between the ultrahigh wavenumber transmission medium 106 and the sample 107 changes in an unpredictable manner during operation, the optical performance is degraded. Therefore, by subjecting the sample-side surface of the ultrahigh wavenumber transmission medium 106 to a process for improving the adhesion with the sample 107, it is possible to prevent deterioration of optical performance. For example, when observing a living cell, the adhesion to the living cell can be improved by coating polylysine on the sample side surface of the ultrahigh wavenumber transmission medium 106.

  FIG. 12 is a graph showing the performance of the ultrahigh wave number transmission medium 106, the near-field light source 105, and the objective lens 108 (light receiving unit) with respect to the frequency of the illumination light. The ultra-high wave number transmission medium 106 represents the performance of each element by normalized resolution, the near-field light source 105 by light emission intensity, and the objective lens by transmittance. The normalized resolution is a value obtained by dividing the maximum spatial frequency that can be transmitted by the ultrahigh wavenumber transmission medium 106 by the spatial frequency corresponding to the wavelength of the illumination light in vacuum. As is apparent from the graph, the frequency bands of the illumination light in which each device exhibits high performance do not always match. However, if the emission band of the near-field light source 105 includes at least a part of the operation band in which the ultrahigh wavenumber transmission medium 106 exhibits a high resolving power, at least a part of the illumination light generated by the near-field light source 105 is The sample surface 107a can be illuminated while being reduced to about the size of the opening 104, and a high resolving power as a near-field optical microscope can be realized. Further, if the band in which the optical system of the objective lens 108 exhibits high transmittance includes at least part of the operating band in which the ultrahigh wavenumber transmission medium 106 exhibits high resolution, the signal light generated on the sample surface 107a is high. It can detect efficiently and can realize high resolving power as a near-field optical microscope.

  FIG. 13 is a schematic diagram for explaining the near-field optical microscope 100 in which the near-field light source 105 is rotatable. The near-field light source 105 is rotatable about a straight line connecting the emission region of the light source 102 and the opening 104 as the rotation axis RA. In operation, the near-field optical microscope 100 rotates the near-field light source 105 with respect to the ultrahigh wavenumber transmission medium 106 using a straight line connecting the opening 104 and the observation point on the sample 107 as a rotation axis RA. For example, when the light source 102 is configured by an element with stimulated emission of light such as a laser diode, the emitted light is coherent light having a uniform wavelength and wavefront, and the polarization state is often linearly polarized. .

  On the other hand, subwavelength imaging elements (materials) such as metamaterials can be used for the ultrahigh wavenumber transmission medium 106, but many of these exhibit strong polarization dependence and high resolution in the polarization direction. However, a relatively low resolving power is shown in the direction orthogonal to this. Therefore, as shown in FIG. 13, if the near-field light source 105 that emits linearly polarized light is rotatable around the rotation axis RA, the signal light that is polarized in various directions is averaged during operation. Since it is detected, the polarization dependence of the ultrahigh wavenumber transmission medium 106 can be canceled and a good image can be obtained. For the purpose of such a rotation operation, it is of course possible to rotate only the light source 102 instead of the near-field light source 105.

  When rotating the near-field light source or the light source, in order to obtain the effect, it is necessary to detect the light accumulated for at least a quarter of the rotation time, that is, the time of a quarter cycle or more of the rotation of the near-field light source 105. There is. Therefore, the light receiving unit 112 further includes a signal light detection unit (not shown). When the rotation speed of the near-field light source 105 (light source 102) is slower than the response speed of the signal light detection unit (for example, a detector such as a photodiode or a photomultiplier tube), the detector side Perform operations such as integrating with.

  Alternatively, the same effect can be obtained by providing polarization conversion means 127 for converting linearly polarized light into circularly polarized light or elliptically polarized light in the near-field light source 105 as shown in FIG. As the polarization conversion means 127, an optical crystal or a liquid crystal element exhibiting an electro-optic effect can be used, and these change the polarization state by changing the optical characteristics as a material in accordance with an electric signal. That is, since there is no mechanical rotation operation or the like, there is no concern about the influence of vibration or a decrease in operation speed. It is also possible to optimize the image obtained by adjusting the polarization state during operation.

  FIG. 15 is a schematic diagram showing a main part of a near-field optical microscope including two near-field light sources, which includes two near-field light sources 105a and 105b. The two near-field light sources 105a and 105b are fixed to a common base 128. When the base 128 is moved by the scanning unit 101, the near-field light source 105a and the near-field light source 105b irradiate points A1 and A2, respectively. The corresponding points B1 and B2 on the sample surface 107a are scanned. Both the signal lights from the points B1 and B2 are detected by the signal light detector 112, but can be distinguished by the wavelength or the polarization state. Or you may distinguish by time division or lock-in detection. Since the near-field excitation unit 122 is a very small device, the scanable region may be limited depending on the design of the scanning unit 101, the mechanical strength of the ultrahigh wavenumber transmission medium 106, or the operation speed. . With the configuration of FIG. 15, the area A is scanned by the near-field light source 105a, and the area B is scanned by the near-field light source 105b. As described above, the area to be scanned by the scanning unit 101 may be approximately half of the case where there is one near-field light source 105, and a wide field of view can be ensured even under such restrictions.

  In addition, electrical control such that the two near-field light sources 105a and 105b emit light alternately, that is, at different timings, can be performed at a very high speed, so that the operation can be speeded up by narrowing the scanning region. . FIG. 15 shows a case where there are two near-field light sources. Of course, three or more near-field light sources may be provided. As the number of near-field light sources increases, the effect of reducing the scanning range or increasing the speed is achieved. Will grow. Furthermore, the same effect as when two near-field light sources are used can also be obtained by providing at least two openings as shown in FIG. In this configuration, since only one light source is required, the manufacturing cost of the near-field optical microscope can be kept low.

  FIG. 17 is a schematic diagram showing a structure in which a fine structure (aperture) and an ultrahigh wavenumber transmission medium are integrated. The opening 104 constituting the fine structure illuminated by the light source 102 forms a light spot having a wavelength smaller than the wavelength, and this light is transmitted to the surface of the sample 107 with almost no diffusion by the ultrahigh wavenumber transmission medium 106. . A part of the fluorescence or scattered light generated on the surface of the sample 107 by the transmitted light enters the objective lens 108 and is detected by a detection means (not shown). In this configuration, since there is no gap between the fine structure, the ultrahigh wave transmission medium 106, and the sample 107, the illumination area on the surface of the sample 107 can be made extremely small, and optical information in a smaller area can be detected. can do.

Further, a two-dimensional image of the surface of the sample 107 can be obtained by moving the integrated structure of the fine structure and the ultrahigh wavenumber transmission medium 106 with respect to the sample 107. At this time, since the light source 102 is fixed at the same position, various noise factors (such as power fluctuation due to vibration) generated by moving the light source 102 can be eliminated. In addition, since the ultra high wavenumber transmission medium 106 is generally a small device having a width of about 100 μm and a thickness of about several μm, it is very lightweight, and scanning by moving the medium has merit in terms of mechanical aspects (scanner size reduction). , High speed).

In the above-described embodiment, the positional relationship between the ultrahigh wave number transmission medium 106 and the sample 107 is substantially the same. In conventional probe type microscopes (near-field optical microscope, atomic force microscope, etc.), it is necessary to scan the probe very close to the sample 107 to be observed, so that a very soft and unstable shape like a living cell is formed. It is not possible to observe the sample it contains, or it requires extremely sophisticated control techniques if possible. However, in the system configuration of the near-field optical microscope 100 according to the present embodiment, the ultra-high wavenumber transmission medium 106 also functions as a cover glass, and the sample surface 107 a is flattened by pressing it against the sample 107. Can be maintained. Speaking from conventional common sense, the cover glass and the probe microscope were incompatible. This is because, in a probe type microscope, in order to obtain a certain level of resolution, it is necessary to bring the probe close to the very vicinity of the sample (distance about the resolution), whereas the cover glass plays a role (flattening of the sample surface 107a). This is because it must have a thickness (at least several μm or more) larger than the resolution in order to achieve the above.

  Since the ultrahigh wave number transmission medium 106 used in this embodiment can transmit a light spot much smaller than the wavelength of light to a distance of several μm or more, it can be used as a cover glass as described above. The limitations of the probe microscope can be removed. That is, the ultrahigh wavenumber transmission medium 106 functions as a key device that combines the high resolution of the probe microscope and the mechanical strength of the cover glass in the near-field optical microscope 100 according to the present embodiment. In the present specification, a configuration in which the sample 107 is scanned by changing the position of the near-field light source 105 or the fine structure (the opening 104) is shown. However, the actual scanning is not the sample 107 but a hard, flat surface. This is an ultra-high wave number transmission medium 106. Therefore, the position with respect to the near-field light source 105 or the ultra-high wavenumber transmission medium 106 having a fine structure may be changed by a preset procedure, and it is not necessary to know the position during operation. In other words, unlike conventional probe microscopes, there is no need to provide means (atomic force detection means, optical lever, resonator, etc.) for knowing the relative position between the probe and the sample, and the microscope system is dramatically reduced in size.・ It is possible to reduce costs and speed.

(Second Embodiment)
FIG. 18 shows an example of the system configuration of a near-field optical microscope according to the second embodiment of the present invention. In FIG. 18, a near-field optical microscope 200 includes an optical system including a light source 202 and an objective lens 203 that form a light irradiation unit for emitting illumination light to a sample 201, a near-field light probe 204, a sample 201, and a fine structure. And an ultra-high wavenumber transmission medium 205 disposed between the near-field optical probe 204 including the H.223. The near-field optical microscope 200 can also be referred to as an optical probe microscope because the optical probe 204 is used.

  Irradiation light emitted from the light source 202 is converted into substantially parallel light by the collimator lens 206, and then condensed on the observation region on the sample 201 by the objective lens 203 through the first half mirror 207. As a result, response light is emitted from a predetermined position of the sample 201.

  Part of the response light emitted from the sample 201 is incident on the objective lens 203 again, is reflected by the first half mirror 207, and enters the observation optical system S1. Further, the image is divided into two by the second half mirror 208, one of which is imaged on the image sensor 210 by the imaging lens 209, and the other is made visible by the eyepiece lens 211.

  The output of the image sensor 210 is subjected to image processing by the image processing unit 212 and supplied to the optical microscope observation monitor 213. Thereby, an image of the sample 201 by the optical microscope is displayed on the optical microscope observation monitor 213, and the state of the sample 201 can be observed in real time. Similar to the first embodiment, such an optical observation method is the same operation as that of a conventional optical microscope using epi-illumination. When the sample 201 has transparency, the opposite side of the optical microscope via the sample 201 is used. In addition, an illuminating unit for transmitting and illuminating the sample 201 can be arranged.

  The sample stage 214 that supports the sample 201 can be freely moved by an actuator 216 controlled by the sample controller 215. Therefore, a light source having good monochromaticity (laser diode or the like) may be used to constitute a laser scanning microscope, a confocal microscope, or a fluorescence microscope.

  Of the response light radiated from the sample 201, the response light radiated to the opposite side of the objective lens 203 with respect to the sample 201 is partially detected by the near-field light probe 204 to generate an electrical signal. Converted. Further, the near-field optical microscope 200 shown in FIG. 18 constitutes a scanning unit for moving the fine structure 223 and the light receiving unit 224 together to change the position of the near-field optical probe 204 with respect to the ultrahigh wavenumber transmission medium 205. And a scanner 218. Further, the near-field optical probe 204, the ultrahigh wavenumber transmission medium 205, and the scanner 218 constitute an optical probe unit 217 indicated by a dotted line in the drawing.

  Although the operation of the optical probe unit 217 will be described later, the optical probe unit 217 performs optical information (reflectance distribution, transmittance distribution, scattering intensity distribution, diffraction) on the surface of the sample 201 without directly scanning the sample 201. It is an imaging device that can detect an efficiency distribution, a concentration distribution of fluorescent proteins, etc.) with sub-wavelength accuracy, which is a spatial distribution finer than the wavelength of irradiation light. The scanner 218 scans the surface of the ultrahigh wavenumber transmission medium 205 under the control of the probe controller 219. As a result, a two-dimensional image signal can be obtained from the light receiving unit 224. The image signal from the light receiving unit 224 is amplified by the preamplifier 220 and sent to the control / display computer 221.

  The operation of the objective lens 203 and the optical probe unit 217 will be described with reference to FIG. Note that the same components as those in FIG. 18 are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 19A, the irradiation light is irradiated to the sample 201 through the glass 222. The ultra-high wavenumber transmission medium 205 has a probe surface 205a and a sample surface 205b, each of which is a wide, rigid plane. The probe surface 205a faces the near-field optical probe 204, and the sample surface 205b faces the sample 201. Has been placed. Here, the ultra-high wavenumber transmission medium 205b is disposed so as to be in contact with the sample 201. The ultra high wavenumber transmission medium 205 can transmit optical information including near-field light in the vicinity of the sample surface 205b, that is, the surface 201a of the sample 201, to the probe surface 205a with high definition. As used herein, “with high definition” means “beyond the optical resolution determined by the diffraction limit”. The optical information transmitted to the probe surface 205 a includes information on the fine structure and optical properties of the surface 201 a of the sample 201, and this is detected by the near-field light probe 204. The near-field optical probe 204 includes a light receiving unit 224 and a fine structure 223. The microstructure 223 is disposed on the incident side of the light receiving unit 224 and has an opening 223a provided in the light shielding member 223b for selectively transmitting near-field light. Further, the light receiving unit 224 detects the near-field light transmitted through the fine structure 223. Therefore, the opening 223a does not directly contact the sample 201. Note that the sample surface 205b of the ultrahigh wavenumber transmission medium 205 is arranged so as to be in contact with the sample 201, but the sample is located at a distance where optical information including near-field light in the vicinity of the surface 201a of the sample 201 is not attenuated. 107 may be arranged. In addition, when the sample surface 205b is pressed against the sample 201 and arranged so that they are in contact with each other, even if the sample is an uneven shape such as a living cell, the ultrahigh wavenumber transmission medium 106 and the sample Since the distance from the terminal 107 can be narrowed, high-definition observation can be performed stably with high resolution.

  FIG. 19B is an enlarged view of the structure around the opening 223a in FIG. 19A. The diameter φ of the opening 223a and the interval δ between the opening 223a and the probe surface 205a are shown in FIG. It is smaller than the wavelength of light. When visible light is used as the irradiation light, the diameter φ of the opening 223a is preferably about 20 to 200 nm. In addition, the interval δ between the opening 223a and the probe surface 205a is preferably 200 nm or less.

  Since the light leaking from the opening 223a of the fine structure 223 and detected by the light receiving unit 224 having the light receiving surface 224a is limited to light in the vicinity of the opening 223a, the near-field optical probe 204 is the probe surface 205a, that is, The surface 201a of the sample 201 can be observed with a very high resolution. The light receiving unit 224 may be a light receiving element made of a known high sensitivity semiconductor light receiving element such as an avalanche photodiode, PIN photodiode, or Schottky photodiode.

  Here, the light receiving unit 224 is not necessarily integrated with the opening 223a. As shown in FIG. 25, the light receiving unit 224 is located at a position where the light from the opening 223a can be detected or on an extension line guided by an optical system, a waveguide, or the like. May be. As shown in FIG. 25, the near-field optical probe does not need to be an aperture type, and a scattering probe 204a that scatters light using a sharp tip or fine particles with high scattering efficiency may be used. 25, the same reference numerals as those in FIG. 30 described above are denoted by reference numerals obtained by subtracting 700 from the reference numerals in FIG. In addition, it is assumed that at least a part of the opening 223a and the ultrahigh wavenumber transmission medium 205 are disposed in the field of view of the optical microscope.

  As described above, the ultrahigh wavenumber transmission medium 205, the near-field optical probe 204 having the fine structure 223 and the light receiving unit 224, and the scanner 218 as the scanning unit are integrally configured as the optical probe unit 217. The scanner 218 includes a fixed portion 225 and a movable portion 226, and the position of the movable portion 226 can be changed with respect to the fixed portion 225 under the control of the probe controller 219. The ultrahigh wavenumber transmission medium 205 is fixed to the fixed part 225, and the near-field optical probe 204 is fixed to the movable part 226. Then, by controlling the scanner 218 with the controller 219, the position of the near-field optical probe 204 can be changed with respect to the ultrahigh wavenumber transmission medium 205. As a configuration of the optical probe unit 217, the ultrahigh wavenumber transmission medium 205, the near-field optical probe 204, and the scanner 218 may be stored in one housing, or these may be fixed to a common column. Also good. In any case, what is necessary for the mechanical operation is that the ultrahigh frequency transmission medium 205 and the fixing portion 225 of the scanner 218 are fixed to each other via a housing or a column, and that the near field That is, the optical probe 204 and the movable portion 226 of the scanner 218 are fixed to each other.

  Next, a specific scanning method will be described. What is important for optical observation is to keep the distance δ between the opening 223a constituted by the fine structure 223 and the probe surface 205a at a distance equal to or smaller than the wavelength of the illumination light, as described above. If this interval changes during scanning, not only the resolving power changes depending on the observation location, but also optical information formed on the probe surface 205a cannot be detected accurately. The scanner 218 is configured so that the position of the fixed portion 225 and the movable portion 226 can be changed only in a plane (xy plane) parallel to the probe surface 205a, and the normal line (z axis) of this plane. The direction is fixed. Further, the distance between the light shielding member 223b of the near-field optical probe 204 and the probe surface 205a of the ultrahigh-frequency transmission medium 205 is set so that the performance (light receiving sensitivity and resolving power) of the near-field optical probe 204 is the highest. . Furthermore, what the near-field optical probe 204 actually scans is not the surface 201 a of the sample 201 but the probe surface 205 a that is an extremely smooth surface of the ultrahigh-frequency transmission medium 205. Therefore, scanning can be performed while maintaining high detection performance regardless of the shape of the surface 201a of the sample 201 and the observation environment. In the conventional near-field optical microscope, it is necessary to control the position with extremely high precision in the z-axis direction in consideration of the unevenness of the sample 201. However, in the configuration of FIG. Thus, it is possible to scan in the xy plane.

  20A and 20B are schematic views showing the arrangement of the optical probe unit 217 and the sample 201. FIG. As shown in FIG. 20 (a), when observing a living tissue such as a living cell in a living state, the surface 201a of the sample 201 is soft and unstable in shape, and the near-field optical probe 204 observes the surface 201a. difficult. Since the optical probe unit 217 according to the present embodiment has a rigid wide bottom surface, even if this bottom surface is pressed against the surface 201a of the sample 201, the optical probe unit 217 is not damaged. Further, since the bottom surface is a planar shape, as shown in FIG. 20B, the surface 201a of the sample 201 to be observed can be deformed into a substantially planar shape by being pressed and brought into close contact with the sample 201. As an optical function, both the ultrahigh wave number transmission medium 205 can transmit a high-definition image from the flat sample surface 205b to the probe surface 205a, so that the near-field optical probe 204 scans the probe surface 205a. Thus, the optical information of the surface 201a of the sample 201 can be observed. Further, since the bottom surface of the optical probe unit 217 is brought into close contact with the sample 201, the air layer for reducing the near light can be thinned, so that the loss of weaker near light can be reduced and observation can be performed with high resolution.

  FIG. 21 is a schematic diagram showing another configuration of the optical probe unit 217 shown in FIG. 19. Basically, the light emitting element 227 is provided in the near-field optical probe 204 in the configuration of FIG. FIG. 18 shows a system configuration in which the near-field light probe 204 and an optical microscope with epi-illumination are used together. However, when observing a transparent sample such as a biological tissue, transmission illumination is often performed. In the configuration shown in FIG. 21, a light emitting element 227 which is an illumination unit for transmitting and illuminating the sample 201 is arranged in the optical probe unit 217. In addition, since the light emitting element 227 is arranged in the optical probe unit 217 that is located very close to the observation region of the sample 201, illumination that is much more efficient than conventional light sources for microscope illumination is possible. Although not shown, a shielding part can be provided between the light receiving part 224 and the light emitting element 227 in order to shield the illumination light. Accordingly, it is possible to block the illumination light from entering the light receiving unit 224 and reduce noise, and as a result, it is possible to acquire an image with a good S / N ratio.

  Further, the near-field light probe 204 has a transmission region 223 c that transmits the illumination light from the illumination unit 227 on the surface facing the ultrahigh wavenumber transmission medium 205. In this way, the bottom surface of the near-field optical probe 204 is not covered with the light shielding member 223b, but the transmission region 223c that transmits the illumination light is provided in a part of the bottom surface. It can be carried out. The reason why such a transmission region 223 c can be provided is that an ultrahigh wavenumber transmission medium 205 having a finite thickness is disposed between the near-field optical probe 204 and the sample 201. The light emitting element 227 is an illumination unit for an optical microscope, but may also serve as an irradiation unit for the near-field light probe 204.

  In FIG. 21, the light receiving unit 224 and the illumination unit 227 are arranged on the same plane. With this configuration, when the light receiving portion 224 is formed on the substrate by a semiconductor process, the light emitting elements 227 on the same plane can be formed at the same time. Since the near-field optical probe 204 is a minute device, manufacturing costs can be significantly reduced by forming a plurality of elements integrally.

  FIG. 22 is a schematic diagram showing still another configuration of the optical probe unit 217 shown in FIG. 19. Basically, in the configuration of FIG. 21, the light emitting element 227 is moved to the side surface of the near-field optical probe 204. It is a thing. The light shielding member 223 b has an illumination reflection surface 223 c for reflecting the illumination light from the light emitting element 227 toward the observation region of the sample 201. Thus, by devising the shape of the light shielding member 223b, the surface 223c can be used as a reflective surface for illumination. A metal is usually used for the light shielding member 223b. However, since the metal exhibits a high reflectance with respect to visible light, high-efficiency illumination can be performed even through the reflective surface 223c for illumination. In addition to direct illumination from the light emitting element 227, the use of reflected light from the reflecting surface 223c for illumination is expected to improve the illumination efficiency, and there is a degree of design freedom regarding the arrangement of the light emitting element 227. Get higher. Note that as described in FIG. 21, a shielding portion for shielding illumination light may be provided between the light receiving portion 224 and the light emitting element 227.

  FIG. 23 is a schematic diagram showing still another configuration of the optical probe unit 217 shown in FIG. In FIG. 23, the optical probe unit 217 includes an ultrahigh wavenumber transmission medium 205 having a surface 205c that has been subjected to a process for improving the adhesion to the sample 201. If comprised in this way, it will become possible to improve the adhesiveness of the optical probe unit 217 and the sample 201, and to perform a more accurate observation. For example, when observing a living cell, the adhesion between the treated sample surface 205c and the living cell can be improved by coating polylysine on the sample surface 205b of the ultrahigh wavenumber transmission medium 205.

Regarding the performances of the near-field optical probe 204, the ultrahigh wavenumber transmission medium 205, and the objective lens 203, the same relationship as in the graph shown in FIG. 12 is recognized. A variable corresponding to the emission intensity of the near-field light source in FIG. 12 is the light receiving sensitivity of the near-field light probe 204. The near-field light probe 204 is normally designed for irradiation light having a predetermined frequency, and the amount of light that can pass through the opening 223a decreases as the frequency of the irradiation light becomes lower. On the other hand, as the frequency increases, the amount of light passing through the opening 223a itself increases, but the proximity of the probe 204 due to a decrease in the transmittance of the optical material inside the probe 204 or a decrease in the light receiving sensitivity of the light receiving unit 224. The light receiving sensitivity as the field light probe 204 decreases. However, if the near-field optical probe 204 has a high light receiving sensitivity band that overlaps at least a part of the operating band in which the ultrahigh wavenumber transmission medium 205 exhibits high resolving power, the signal light generated on the sample surface 201a is highly sensitive. And can achieve high resolving power as a near-field optical microscope. Similarly to the first embodiment, if the band in which the optical system of the objective lens 203 exhibits high transmittance includes at least a part of the operating band in which the ultrahigh wavenumber transmission medium 205 exhibits high resolution, the sample surface The signal light generated in 201a can be detected with high efficiency, and high resolving power as a near-field optical microscope can be realized.

  As described above, in order for the near-field optical microscope to operate as an optical device exhibiting high resolution, the transmission band of the near-field optical probe 204 (the frequency region in which the near-field optical probe 204 exhibits high light receiving sensitivity) The high wavenumber transmission medium 205 includes at least a part of the operating band exhibiting high resolving power (standardized resolution). As the transmission band, for example, a band having a transmittance of −3 dB or more of peak intensity is used.

  Further, as shown in FIG. 18, the objective lens 203 is provided for optical microscope observation, but also serves as a part of a light irradiating part for sample observation by the optical probe unit 217. Thus, as in the first embodiment, the entire system can be reduced in size by sharing the objective lens 203 between the optical microscope and the optical probe unit 217. When it is necessary to provide the irradiation light to the optical probe unit 217 independently, a light source for that purpose can be provided in the optical microscope optical system, and the sample 201 can be irradiated through the objective lens 203.

  As shown in FIG. 24, the objective lens 203 is normally designed to transmit the entire visible light range, but when the frequency becomes too high, an optical material such as glass constituting the objective lens 103 transmits light. Disappear. On the other hand, if the frequency is too low, the refractive index of the optical material deviates from the design value, so that the effective transmitted light amount decreases or the performance as the objective lens 103 decreases due to an increase in aberration.

  Therefore, in order for the near-field optical microscope to operate as an optical device exhibiting high resolution, the transmission band of the optical system of the irradiation unit includes at least a part of the operation band in which the ultrahigh wavenumber transmission medium 205 exhibits high resolution. It is preferable. In particular, since the objective lens 203 constituting the optical system of the irradiation unit for the optical probe unit 217 generally has a large number of lenses, a multi-layer coating is applied to increase the transmittance in the target wavelength range, thereby limiting the transmission band. Has been. Even when the objective lens 203 is used in a low band, normal operation can be performed by using a high-output light source. However, in this case, problems such as an increase in the size of the light source, heat generation due to irradiation light, and increase in noise light occur.

As an example of sharing the objective lens 203, a case where the sample 201 is observed with fluorescence will be described. As shown in FIG. 19, the optical probe unit 217 detects the fluorescence emitted from the sample 201 (fluorescent dye) that has irradiated the excitation light through the objective lens 203 and absorbed it as response light. At this time, the excitation light transmitted through the sample 201 usually becomes noise light and inhibits fluorescence observation. Moreover, since the excitation light usually has a very strong intensity of 10 ⁴ to 10 ⁶ times that of fluorescence, it is rare to use transmitted illumination as shown in FIG. 19 in fluorescence observation. However, as shown in FIG. 24, since the ultra high wavenumber transmission medium exhibits strong frequency selectivity, it functions as a powerful filter that reflects and absorbs excitation light and transmits fluorescence. Can be done automatically.

  Here, the optical performance of the ultrahigh wavenumber transmission medium in the present invention will be described in detail. The ultra-high wave number transmission medium 105 is made of at least two different materials, and exhibits extremely high resolution for a predetermined frequency. Even if the dielectric constant (permeability) of each material slightly changes in accordance with the change in frequency, the effective dielectric constant (permeability) of the ultrahigh wavenumber transmission media 106, 205, 302 changes greatly. For this reason, the band in which the ultrahigh wavenumber transmission media 106, 205, and 302 exhibit high resolution is narrow.

  As described above, the ultra high wavenumber transmission media 106, 205, and 302 transmit optical information in the vicinity of the surfaces on the sample side, that is, the surfaces 107 a, 201 a, and 301 a of the samples 107, 201, and 301, to the probe side (first implementation). In the embodiment, the light can be transmitted to the surface 205a. The ultrahigh wavenumber transmission media 106, 205, and 302 can be formed of a medium having a negative effective dielectric constant, magnetic permeability, or refractive index by an artificial structure called a metamaterial, for example. This makes it possible to transmit or amplify an evanescent wave that cannot be attenuated and transmitted in the air.

  Further, the ultra high wavenumber transmission media 106, 205, and 302 can be configured using a medium having strong anisotropy. Such anisotropy can be manifested, for example, by a structure in which a metal and a dielectric are alternately laminated with a period shorter than the wavelength of light. Alternatively, an ultrahigh wavenumber transmission medium can be configured using a medium whose effective refractive index is set to a very large value by a metamaterial. Even if the dielectric constant takes a positive value both in the xy plane and in the z-axis direction, if the dielectric constant in the z-axis direction is large, the diffraction limit can be relaxed although it is limited. .

Next, the dispersion characteristics of an anisotropic medium that can constitute the ultrahigh wavenumber transmission media 106, 205, and 302 will be described. In the following description, the dielectric constant ε (each component of the dielectric constant tensor ε ^) and the magnetic permeability μ (each component of the magnetic permeability tensor μ ^) are respectively relative to the dielectric constant ε ₀ and the magnetic permeability μ _{0 in} vacuum. It is expressed as a ratio (relative dielectric constant and relative permeability). However, ε ^ indicates that “^ (hat)” is attached to ε. Similarly, μ ^ indicates that “^ (hat)” is placed on μ.

In an anisotropic medium that electrically exhibits uniaxial anisotropy, the direction of the optical axis is the z-axis. The optical axis is a term relating to the electromagnetic property of the medium, and is a term completely different from the optical axis of the optical system. This specification deals with a case where the dielectric constant or permeability has a uniaxial anisotropy, that is, an anisotropy having only one symmetry axis, and this symmetry axis is called an optical axis. To do. However, even if there is a slight difference in ε between the x-axis direction and the y-axis direction, any material may be used as long as it has the same properties as an ultrahigh wavenumber transmission medium. For example, the isofrequency curve on the k _x -k _z plane and the isofrequency curve on the k _y -k _z plane are both ellipses having a minor axis on the k _z axis, and the length of the semimajor axis is 5 k. _{When the} frequency is ₀ or more, or when the iso-frequency curve on the k _x -k _z plane and the iso-frequency curve on the k _y -k _z plane are both hyperboloids, the super high wave number transmission medium is also used. Since any direction is equivalent in a plane perpendicular to the z-axis, which is the optical axis, an arbitrary direction in this plane is defined as the x-axis, and a direction perpendicular to the x-axis and z-axis is defined as the y-axis. When the coordinate system is defined in this way, the dielectric constant tensor of a medium exhibiting electrical uniaxial anisotropy is expressed as follows.

  Consider the propagation of TM (Transverse Magnetic) waves in this anisotropic medium. The TM wave means a state of an electromagnetic wave in which the magnetic field is directed in the y-axis direction. Assuming a monochromatic plane wave having a wave vector k and an angular frequency ω in the wave equation for the TM wave, the following dispersion relationship is obtained.

Expression (3) is an absolute value of a vector obtained by projecting the wave vector k onto the xy plane. Incidentally, k ₀ is the wave number of the light wave of angular frequency ω propagating in vacuum is expressed as follows.

FIG. 26 is an equifrequency curve depicting the trajectories of k _T and k _Z that satisfy Equation (2) when various values of ε _T and ε _Z are given. FIG. 26A shows the case of ε _T = 1, ε _Z = 1 (dispersion in vacuum), the case of ε _T = 9, ε _Z = 9 (hereinafter, high refractive index), and ε _T = 1, An equifrequency curve for the case of ε _Z = 25 (hereinafter referred to as normal anisotropy) is shown. An equal frequency curve or an equal frequency curved surface represents a wave vector that can be taken by an electromagnetic wave propagating in a medium with respect to a certain frequency. Since the wave vector is generally a three-dimensional vector, the trajectory of the wave vector that has three components (k _x , k _y , k _z ) and is allowed to exist as an electromagnetic wave is a curved surface. On the other hand, as shown in FIG. 26, when focusing only on the two components k _T and k _z of the wave vector, a set of values allowed as these two components can be expressed as a curve in the plane.

When a medium having anisotropy is used as an ultrahigh wave number transmission medium and its optical axis (z-axis) coincides with the image transmission direction, the fineness of information to be transmitted (spatial frequency) is k _T expressed. In FIG. 26A, in dispersion in a vacuum, there is a value of k _Z corresponding to k _T when | k _T | ≦ k ₀ . This means that a light wave carrying such optical information can propagate in the z direction. However, for | k _T |> k ₀ there is no corresponding value of k _Z. Therefore, the light wave carrying such information cannot propagate in the z direction (does not contribute to the formed image). From equation (2), in this case k _Z is purely imaginary, that is, in the z-direction it is understood that the evanescent wave decays exponentially. In this way, optical information with a high spatial frequency is lost, and a phenomenon in which the transmitted image is different from the original object (light source) is called a diffraction limit, which is one element that limits the resolving power of the optical microscope.

In FIG. 26 (a), the case of normal anisotropy, | _{k T} | in the range of ≦ 5k _0, the value of _{k Z} corresponding to _{k T} is present. This means that a light wave carrying such optical information can propagate in the z direction. Therefore, the upper limit of the spatial frequency that can be transmitted is 5 times that in the case of vacuum, and the resolution of the optical system can be improved.

Each point on the equifrequency curve represents the wave number vector of the electromagnetic wave that can propagate as a wave, and the group velocity of the electromagnetic wave is defined at each point. According to the mathematical treatment of electromagnetic waves, the group velocity coincides with the normal direction of the iso-frequency curve. The direction of the group velocity is indicated by an arrow in FIG. In normal anisotropic material having an increased range of transmission capable k _T, the group velocity in many respects on the equal-frequency curve is seen to have an orientation close to the optical axis (z-axis). This tendency becomes more pronounced as longer the k _T direction of an ellipse. Therefore, the light receiving section and the opening are installed so that the optical axis of the ultrahigh wave number transmission medium coincides with a straight line connecting the opening and at least a part of the light receiving surface of the light receiving section.

On the other hand, optical materials (dielectric materials) such as glass and plastic have a refractive index of about 1.3 to 2.1 with respect to visible light, and optical materials with a refractive index exceeding 3 are not found in nature. not exist. The iso-frequency curve for the high refractive index in FIG. 26 (a) represents a dielectric having a refractive index of 3. In this case, the upper limit of k _T that may be transmitted, tripled compared with the case in vacuum. In known immersion lenses and solid immersion lenses, the resolution of the microscope is improved by increasing the effective numerical aperture (NA) due to a high refractive index. However, the resolving power of the high refractive index material is up to about the refractive index of the material used as the medium, and a resolving power exceeding three times that for imaging in vacuum cannot be obtained.

On the other hand, for example, when a medium having dielectric anisotropy derived from an artificial structure is used, the effective dielectric constant ε _Z in the z-axis direction is much higher than 9 (a value that can improve the resolution three times). The resolution can be increased, and higher resolution can be obtained than when a high refractive index material is used.

Here, it is generally said that the limit of the resolving power is approximately λ / 2 when the wavelength of the irradiation light (illumination light) used in the optical microscope is λ. This is because, when forming an image with a lens capable of transmitting light having a wave number of | k _T | ≦ k ₀ , the two point light sources on the object plane can be recognized as two point images. This means that the minimum distance is approximately λ / 2.

On the other hand, the smallest dimension of observable structure under a microscope, believed inversely proportional to the upper limit of the wave number k _T which can be transmitted from the object plane to the image plane. Therefore, if an optical element capable of transmitting all light having a wave number of | k _T | ≦ 5k ₀ is used, a very high-performance microscopic observation apparatus capable of optically observing a fine structure having a wavelength of about 1/10 is obtained. It can be realized.

FIG. 26 (b) illustrates the equifrequency curve of Equation (2) for the case where the signs of the two types of components ε _T and ε _Z appearing in the dielectric constant tensor are different. That is, a case where ε _T <0 and ε _Z > 0 (hereinafter referred to as negative positive anisotropy) and a case where ε _T > 0 and ε _Z <0 (hereinafter referred to as positive / negative anisotropy) are shown. It is a thing. The dotted line in FIG. 26 (b) shows the hyperbolic asymptote. The asymptote is expressed by equation (5) in the case of positive and negative anisotropy, and by equation (6) in the case of negative positive anisotropy. As described above, since the x-axis and the y-axis are equivalent, in the three-dimensional space, the hyperbola becomes a rotational hyperboloid and the asymptote becomes a conical surface. When there is a slight difference in ε between the x-axis direction and the y-axis direction, the hyperbola and the curved surface corresponding to the asymptotic line do not become a rotating body. This is called a curved surface.

The direction of the group velocity of the light wave is indicated by an arrow with respect to the positive / negative anisotropy of FIG. The direction of the group velocity is distributed in a range from the direction of the optical axis to the direction of the normal line of the two asymptotes expressed by Expression (5). Therefore, the light receiving unit needs to be installed on the optical axis passing through the opening. To reduce the coefficient of asymptote of formula (5), by performing the asymptote approaches k _x axis (asymptotic curved approaches k _x k _y plane) as a material designed to concentrate the light waves more the optical axis direction Thus, it can be efficiently detected by a smaller light receiving unit. Most of the light waves propagate at an angle close to the normal of the asymptotic surface. Therefore, the light receiving part and the opening part are parallel to the normal of the asymptotic curved surface, and the optical axis of the ultrahigh wavenumber transmission medium coincides with a straight line connecting the opening part and at least a part of the light receiving surface of the light receiving part. Install.

If positive and negative anisotropic, optionally (but real) the value of k _Z corresponding to k _T is present as a real number, that theoretically, propagates the light wave played optical information with any number higher spatial frequencies Can do.

On the other hand, in the case of negative positive anisotropy, in contrast to light wave propagation in a vacuum, when | k _T | <1, the light wave becomes an evanescent wave (k _Z is a pure imaginary number). All the optical information in the range of _T | ≧ 1 is transmitted. Therefore, when imaging is performed through a medium exhibiting negative positive anisotropy, optical information corresponding to | k _T | <1 is lost, and it is difficult to obtain good imaging performance.

However, when propagating a light wave that has passed through an opening having a diameter smaller than the wavelength, there is little optical information corresponding to | k _T | <1 at the stage of passing through the opening, and optical information that forms the light wave. Has many high spatial frequencies in the range of | k _T | ≧ 1. Therefore, the effect of losing the spatial frequency component of | k _T | <1 in a medium exhibiting negative positive anisotropy is relatively small, and it is possible to perform good transmission of optical information. In this case, the main part of the propagation direction is the normal direction of the asymptotic surface of the hyperboloid with the axial direction as the center. By designing the material so that the asymptotic curved surface is closer to the xy plane, the propagating light can be more concentrated in the optical axis direction. The light receiving section and the opening are installed so that the optical axis of the ultrahigh wave number transmission medium coincides with a straight line connecting the opening and at least a part of the light receiving surface of the light receiving section. Furthermore, it is effective to install the light receiving surface on a line extending from the opening in the normal direction of the hyperbolic asymptotic surface.

From the above, if an ultrahigh wavenumber transmission medium is configured using an anisotropic medium, the following effects can be obtained from the dispersion characteristics. In other words, the known immersion lens and solid immersion lens can only improve the resolution of the optical system up to about three times. On the other hand, if a medium having an effective dielectric constant is used and optical information is transmitted in the direction of the optical axis, for example, the wave number in the plane perpendicular to the optical axis is 0 to 5 k. Light waves in the range of ₀ can be propagated, and the resolving power of the optical system can be improved five times. In addition, if the medium has a stronger anisotropy in the effective dielectric constant and the dielectric constant tensor component has a different sign between the optical axis direction and a plane perpendicular to the optical axis, the resolving power of the optical system Can be further improved, and there is no theoretical restriction on the resolution.

  As described above, when components having different signs exist in the dielectric constant tensor, they can be roughly classified into negative positive anisotropy and positive negative anisotropy. A medium exhibiting negative / positive anisotropy can be used for a device that collects light waves that have passed through an opening, such as a near-field optical probe, and a medium exhibiting positive / negative anisotropy is used for near-field light. It can be used as an imaging element for general imaging devices as well as probes.

  Although the TM wave has been described above, the same applies to the TE wave (the state of the electromagnetic wave in which the electric field is directed in the y-axis direction) if the dielectric constant and the magnetic permeability are replaced. In other words, if the effective magnetic permeability has anisotropy and the z-axis is taken in the direction of the optical axis, the magnetic permeability tensor is expressed as in equation (4). It becomes like (5).

Therefore, positive and negative anisotropy is realized by μ _T > 0 and μ _Z <0, and positive and negative anisotropy is realized by μ _T <0 and μ _Z > 0.

In the above description of the anisotropy with respect to the TM wave, it is assumed that μ _y > 0 in Equation (2). However, even if μ _y <0, light transmission is possible if there is strong anisotropy. That is, as is clear from the above description, assuming μ _y <0, if the dielectric constant has positive and negative anisotropy, that is, if ε _T > 0 and ε _Z <0, | k _T | ≧ Light that satisfies 1 can be transmitted. When the dielectric constant has negative positive anisotropy, that is, when ε _T <0 and ε _Z > 0, light having an arbitrary k _T can be transmitted. The same applies to the TE wave, and assuming that ε _y <0, if the magnetic permeability has positive and negative anisotropy, that is, if μ _T > 0 and μ _Z <0, | k _T When light satisfying | ≧ 1 can be transmitted and the magnetic permeability has negative positive anisotropy, that is, when μ _T <0 and μ _Z > 0, light having an arbitrary k _T can be transmitted. .

Hereinafter, an artificial structure that provides an effective dielectric constant with anisotropy will be described. FIG. 27 is a conceptual diagram of an example structure. This structure is composed of a metal dielectric multilayer film 33 in which metals 31 and dielectrics 32 are alternately laminated. 27, the dielectric constant of the metal 31 epsilon _m, the dielectric constant of the dielectric 32 and epsilon _d, the thickness _d m respectively, when alternately stacked with _{d d,} the thickness _d m, _{d d} are both irradiated If it is sufficiently smaller than the wavelength of light, the entire metal dielectric multilayer film 33 can be regarded as an electromagnetically homogeneous anisotropic medium. The effective dielectric constant tensor of this anisotropic medium is given by the following equation (9).

In the equation (6), in the optical frequency band including visible light, most of the metal 31 has a negative dielectric constant ε _m (real part), and the dielectric constant ε _d (real part) of the dielectric is positive. The real number of Therefore, the thickness d _m of the layers to be _laminated, by suitably selecting the d _d, it may also be a component of the effective dielectric constant of the metal dielectric multilayer film 33 in the negative to positive. An example of an effective dielectric constant component of the metal dielectric multilayer film 33 is shown in FIG.

In FIG. 28, the metal 31 of the metal dielectric multilayer film 33 is silver, the dielectric 32 is aluminum oxide, and the ratio d of the metal 31 in the total thickness of the metal dielectric multilayer film 33 is expressed by the following formula ( The effective dielectric constant components Re (ε _T ) and Re (ε _Z ) when changed according to 10) are illustrated. In addition, the wavelength of irradiation light was 365 nm and 517 nm.

In the case of FIG. 28, when the wavelength of the irradiation light is 365 nm, Re (ε _T )> 0 and Re (ε _Z ) <0 in the range of 0.47 ≦ d ≦ 0.55, and the wavelength of the irradiation light is At 517 nm, Re (ε _T ) <0 and Re (ε _Z )> 0 in the range of 0.26 ≦ d ≦ 0.74. Thus, by appropriately selecting the material of the metal 31 and the dielectric 32, a component having a dielectric constant tensor or all components having a positive or negative value with respect to light having a predetermined wavelength (frequency) is selected. Can be.

  FIG. 29 is a conceptual diagram illustrating another example of an artificial structure that provides an effective dielectric constant with anisotropy. In this structure, an artificial anisotropic medium is constituted by the metal nanorod array 301. A cylindrical metal nanorod 302 having a cross section smaller than the wavelength of irradiation light (with radius r and length longer than the wavelength). Are arranged in a square lattice with a period a smaller than the wavelength. In this case, similarly to 36, when r, a << λ (λ is the wavelength of irradiation light), it is allowed to be regarded as a homogeneous medium having anisotropy electromagnetically.

As is clear from the structure of the metal nanorod array 41 shown in FIG. 29, the optical axis as the anisotropic medium coincides with the z axis (the same direction as the symmetry axis of the metal nanorod 42). Here, if the metal nanorod 42 is sufficiently long, a current flows in the direction of the optical axis (free electrons in the metal can move), and thus there is an electrical response that depends on the type of metal. In this case, assuming that the electrical conductivity of the metal material constituting the metal nanorod 42 is σ and the plasma frequency is ω _P , the component of the dielectric constant in the optical axis direction when the metal nanorod array 41 is regarded as a homogeneous anisotropic medium. Is given by:

As is clear from the equation (11), in the case of the metal nanorod array 42, by appropriately selecting the metal type (ω _P and σ), the structure of the array (a and r), or the angular frequency ω, the optical The effective dielectric constant in the axial direction can be positive or negative.

  On the other hand, in the frequency band of light, regardless of metals and dielectrics, most materials in nature do not show a magnetic response. For this reason, the magnetic permeability cannot be made anisotropic by a structure such as the multilayer film or nanorod. However, in recent years, a medium that can change the permeability in the frequency band of light using an artificial structure has been proposed, and the real part of the effective permeability can be set to a negative value. Yes. As an example, a split ring resonator which is a kind of artificial structure called a metamaterial is known.

The present invention is not limited to the above-described embodiment, and many variations or modifications are possible. For example, in the configuration of the second embodiment shown in FIG. 17, when one point on the sample is observed, the scanner and the probe controller are not necessary.

100, 200 Near-field optical microscope 103, 223b Light-shielding member 104, 123a Aperture 106, 205 Ultrahigh wave number transmission medium 108, 203 Objective lens 112, 224 Light-receiving unit

Claims (35)

A light irradiation unit for emitting illumination light to the sample;
A light receiving portion for receiving light;
A microstructure that is disposed on at least one of the emission side of the light irradiating unit and the incident side of the light receiving unit, and that generates or selectively transmits near-field light; and
An ultrahigh wavenumber transmission medium that exhibits anisotropy in dielectric constant or magnetic permeability and transmits near-field light;
A near-field optical microscope. The fine structure is disposed on the exit side of the light irradiation unit to generate near-field light,
The near-field optical microscope according to claim 1, wherein the ultra-high wavenumber transmission medium transmits near-field light generated by the fine structure and emits the illumination light to the sample as the illumination light. The ultra high wavenumber transmission medium is disposed between the sample and the microstructure;
The fine structure is disposed on the incident side of the light receiving unit and transmits the near-field light,
The near-field optical microscope according to claim 1, wherein the light-receiving unit detects the near-field light transmitted through the fine structure.   The near-field optical microscope according to claim 1, wherein the fine structure has an opening smaller than a wavelength of the illumination light.   The near-field optics according to any one of claims 1 to 4, wherein, in operation, a distance between the fine structure or the opening and the ultrahigh wavenumber transmission medium is kept below the wavelength of the illumination light. microscope.   The near-field optical microscope according to claim 1, wherein the ultrahigh wavenumber transmission medium is disposed so as to contact the sample during operation.   The near-field optical microscope according to claim 1, further comprising a scanning unit for changing a position of the fine structure with respect to the ultrahigh wavenumber transmission medium.   The near-field optical microscope according to claim 1, wherein the light source and the fine structure are integrally configured as a near-field light source.   The near-field optical microscope according to claim 8, further comprising a scanning unit for changing a position of the near-field light source with respect to the ultrahigh wavenumber transmission medium.   The near-field optical microscope according to claim 9, wherein the near-field light source, the ultra-high wavenumber transmission medium, and the scanning unit are integrally configured. The light receiving unit has an objective lens,
An optical microscope including the objective lens;
The near-field optical microscope according to any one of claims 4 to 10, wherein at least a part of the opening and the ultrahigh wavenumber transmission medium are arranged in a field of view of the optical microscope.   The near-field optical microscope according to claim 11, further comprising an illumination unit for an optical microscope that is disposed on the opposite side of the optical microscope with respect to the sample and illuminates the sample.   The optical microscope illumination unit includes the near-field light source, the ultrahigh-wavenumber transmission medium, and a scanning unit for changing the position of the near-field light source with respect to the ultrahigh-wavenumber transmission medium. The near-field optical microscope according to claim 12, which is disposed inside. The opening is formed in a part of the light shielding member;
14. The near-field optics according to claim 12, wherein the near-field light source has a transmission region that transmits the optical microscope illumination light from the illumination unit for the optical microscope on a surface on the side facing the ultrahigh wavenumber transmission medium. microscope.   The proximity according to any one of claims 12 to 14, further comprising a shielding unit that shields the illumination light for the optical microscope from the illumination unit for the optical microscope, between the light source and the illumination unit for the optical microscope. Field optical microscope.   The near-field optical microscope according to any one of claims 1 to 15, wherein the ultra-high wavenumber transmission medium has a treated surface that has been subjected to a treatment for enhancing adhesion to the sample.   At least one of a light emission band of the near-field light source, a transmission band of the optical system of the light receiving unit, and a transmission band of the objective lens includes a part of an operation band in which the ultrahigh wavenumber transmission medium exhibits high resolving power. The near-field optical microscope as described in any one of Claims 6-16.   The operation according to any one of claims 8 to 17, wherein the near-field light source is rotated with respect to the ultrahigh wavenumber transmission medium with a straight line connecting the opening and an observation point on the sample as a rotation axis. Near-field optical microscope.   19. The near-field optics according to claim 18, wherein the light receiving unit further includes a signal light detection unit, and the detection unit integrates and detects the signal light over a period of ¼ period or more of the rotation of the near-field light source during operation. microscope   The near-field optical microscope according to claim 8, wherein the near-field light source emits circularly polarized light or elliptically polarized light.   The near-field optical microscope according to claim 1, further comprising a polarization conversion element that converts light emitted from the light source into circularly polarized light or elliptically polarized light. Comprising at least two said near-field light sources,
The near-field optical microscope according to claim 8, wherein a plurality of near-field light sources emit light at different timings during operation.   The near-field optical microscope according to claim 4, comprising at least two openings.   The near-field optical microscope according to claim 1, wherein the fine structure and the ultrahigh-frequency transmission medium are integrally formed.   The near-field optical microscope according to any one of claims 1 to 24, wherein a value of a real part of at least one component of an effective dielectric constant tensor or a magnetic permeability tensor of the ultrahigh wavenumber transmission medium is negative.   The near-field optical microscope according to any one of claims 1 to 24, wherein a value of a real part of at least one component of an effective dielectric constant tensor or a magnetic permeability tensor of the ultrahigh wavenumber transmission medium is 25 or more. .   The near-field optical microscope according to claim 1, wherein the fine structure and the light receiving unit are integrally formed.   28. An illuminating unit for transmitting and illuminating a sample, and a scanning unit that moves the illuminating unit, the fine structure, and the light receiving unit integrally to change a position with respect to the ultrahigh-frequency transmission medium. The near-field optical microscope described in 1.   29. The near-field optical microscope according to claim 28, wherein the fine structure, the light receiving unit, the ultrahigh wavenumber transmission medium, and the scanning unit are integrally configured. The microstructure has an opening, and the opening is formed by a light shielding member,
30. The near-field optical microscope according to claim 28 or 29, wherein the fine structure has a transmission region through which illumination light from the illumination unit is transmitted on a surface on a side facing the ultrahigh wavenumber transmission medium.   The near-field optical microscope according to claim 28, wherein the light receiving unit and the illumination unit are arranged on the same plane.   The near-field optical microscope according to any one of claims 28 to 31, further comprising a shielding unit that shields illumination light from the illumination unit between the light receiving unit and the illumination unit. A dielectric constant or a magnetic permeability showing anisotropy, and a step of closely adhering an ultrahigh wavenumber transmission medium that transmits near-field light to a sample;
Irradiating the sample with light;
Receiving the light emitted from the ultra-high wavenumber transmission medium in close contact with the sample through a fine structure.   34. The sample observation method according to claim 33, wherein an interval between the ultrahigh wavenumber transmission medium and the fine structure is kept below a wavelength of light irradiated on the sample.   The sample observation method according to claim 33 or 34, further comprising a step of changing a position of the fine structure with respect to the ultrahigh wavenumber transmission medium.

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