JP2006201115A - Optical fiber type surface plasmon resonance sensor and optical fiber type surface plasmon resonance sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain only a broad resonance absorption spectrum in a conventional optical fiber type surface plasmon resonance sensor device, and therefore, it is difficult to measure and analyze a surface plasmon resonance absorption wavelength.
In the present invention, an optical fiber is bent at a predetermined angle that satisfies the total reflection condition, and at least a peak-side core of the bent portion is exposed from the clad to form a flat portion, and surface plasmon resonance is formed in the flat portion. Such a problem has been solved by constructing an optical fiber type surface plasmon resonance sensor in which a metal thin film for generating the above is formed.
[Selection] Figure 2

Description

  The present invention relates to an optical fiber type surface plasmon resonance sensor and an optical fiber type surface plasmon resonance sensor device.

  In the metal, free electrons collectively vibrate to generate a dense wave called a plasma wave. Quantized coarse waves generated on the metal surface are called surface plasmons.

  Various surface plasmon resonance sensor devices that detect a substance in a sample by utilizing the phenomenon that the surface plasmon is excited by a light wave have been proposed.

  Particularly well-known among them is, for example, one using an optical system called a Kretschmann arrangement, whose conceptual diagram is shown in FIG.

  In this system, as shown in FIG. 8, a metal thin film b such as gold or silver is formed on the surface of the prism a, and an angle that satisfies the total reflection condition from the prism a side toward the interface with the metal thin film b. That is, when the incident light c is irradiated at the incident angle θ, the surface plasmon f is excited on the metal thin film b at a specific incident angle θsp.

  When surface plasmon is excited on the metal thin film b, light energy is resonantly absorbed thereby, so that the intensity of the reflected light d totally reflected at the interface between the prism a and the metal thin film b is significantly reduced, as shown in FIG. To do. FIG. 9 shows the relationship between the incident angle θ and the intensity of the reflected light d, in this case, the reflectance in the configuration of FIG.

  Here, since the incident angle θ at which surface plasmon resonance occurs depends on the medium density of the measurement unit e in contact with the metal thin film b, the intensity of the reflected light d reflected from the optical system is specific. By calculating the reflection angle that decreases to the above, it is possible to determine the presence or absence of the surface plasmon resonance phenomenon and the incident angle θ when this phenomenon occurs, and accordingly, the density of the medium of the measurement unit e, that is, the metal thin film b Changes in the surface mass can be detected.

  By utilizing the surface plasmon resonance phenomenon in this way, a slight change in the mass of the surface of the metal thin film b is caused by a change in light intensity due to surface plasmon resonance absorption of the metal thin film b or an incident angle θ at which surface plasmon resonance absorption occurs. Change can be detected with high sensitivity. For example, even a very small amount of mass change of 1 picogram level can be detected.

  For this reason, the surface plasmon resonance sensor is applied to the biochemical field that handles minute changes that are difficult to measure by a general measurement method.

  Various types of surface plasmon resonance sensors have been proposed, and one of them uses an optical fiber.

  For example, Patent Literature 1 and Patent Literature 2 show an example of an apparatus using an optical fiber type surface plasmon resonance sensor, and its configuration will be described with reference to FIG.

  Reference numeral g denotes an optical fiber, for example, a step index type multimode optical fiber. As shown in an enlarged view in the drawing, the core i is exposed by removing the cladding h at the tip, and the exposed core i A metal thin film j is formed on the surface to constitute a sensor. An optical fiber g having a sensor portion k at the tip is connected to an optical fiber n on the light source m side and an optical fiber p on the detector o side through a beam splitter l to constitute an optical fiber type surface plasmon resonance sensor device. is doing. The symbol q is a condenser lens.

In such an optical fiber type surface plasmon resonance sensor device, a sample is placed at a predetermined position with respect to the sensor part k, white light is introduced from the light source m through the condenser lens q to the optical fiber n, and the beam splitter l is used. Are introduced into the optical fiber g. Then, the reflected light from the sensor unit k is introduced from the beam splitter l through the optical fiber p to the detector o, and its wavelength characteristic is detected. That is, this utilizes the wavelength dependence of light of the surface plasmon resonance sensor, and when the incident angle θ at the interface between the core i of the sensor part k and the metal thin film j is constant, the resonance absorption spectrum relating to wavelength dispersion. Is obtained. By measuring and analyzing the surface plasmon resonance absorption wavelength in this way, a very small amount of mass change of the sample is detected.
Japanese Patent No. 29389973 Japanese Patent Application Laid-Open No. 11-223597

  In the conventional optical fiber type surface plasmon resonance sensor device described above, the light incident on the optical fiber g has various incident angle components depending on the characteristics of the optical fiber g, and the obtained surface plasmon resonance absorption spectrum is obtained. Since each of the incident angle components is added, only a broad resonance absorption spectrum can be obtained. Therefore, it is difficult to measure and analyze the surface plasmon resonance absorption wavelength.

  On the other hand, in order for the light introduced into the optical fiber g to be reflected by the sensor unit k, a certain length or more is required, and below that, a change in light intensity due to surface plasmon resonance absorption cannot be detected. On the other hand, in the prior art, it is very difficult to form a uniform metal thin film because the metal thin film must be formed on the exposed surface of the core of a certain length or longer, that is, a curved surface.

  In addition, the surface plasmon resonance sensor device is mainly used for measurement targeting biochemical reactions. In this case, substances other than biochemical reactions are physically adsorbed on the sensor unit. Since the resonance absorption spectrum is also changed depending on factors, at least two channels of a sensor for detecting a target biochemical reaction and a reference sensor are required.

However, in the conventional device described above, if two or more channels of sensors are to be configured, two or more devices are required, which is not realistic from the viewpoints of space and cost.
The present invention aims to solve such problems.

  In order to solve the above-described problems, in the present invention, first, the optical fiber is bent to a predetermined angle that satisfies the total reflection condition, and at least the peak-side core of the bent portion is exposed from the clad to form a plane portion, An optical fiber type surface plasmon resonance sensor is proposed in which a metal thin film for generating surface plasmon resonance is formed on a flat surface.

  In the present invention, in the above sensor, it is proposed that the core has a structure in which only the flat portion is exposed from the clad to form a metal thin film, or the core has a bent portion and its vicinity exposed from the clad. To do.

  In the present invention, it is proposed that the above-described sensor has a configuration in which the bent portion of the optical fiber and its vicinity are covered with a light-shielding film except for the portion where the metal thin film is formed.

  In the present invention, it is proposed that in the above sensor, the light-shielding film is a metal film, an organic film, or an inorganic film.

  Next, in the present invention, a light source unit for injecting monochromatic light such as white light, infrared light, or laser is disposed on one end side of the optical fiber constituting the optical fiber type surface plasmon resonance sensor described above, and the other end An optical fiber type surface plasmon resonance sensor device is proposed in which a detector for detecting light passing through the bent portion is disposed on the side.

  The present invention also proposes that the above-described optical fiber type surface plasmon resonance sensor is configured at a plurality of positions of the optical fiber from the one end side where the light source unit is arranged to the other end side where the detection unit is arranged in the above-described apparatus. To do.

  The present invention also proposes that the optical fiber type surface plasmon resonance sensor configured at a plurality of locations in the above apparatus is configured by connecting a plurality of single optical fiber type surface plasmon resonance sensors in series.

  Further, in the present invention, in the above-described apparatus, the optical fiber type surface plasmon resonance sensor configured at a plurality of locations has a configuration in which at least one of the angle of the bent portion, the material of the metal thin film, and the thickness of the metal thin film is different. Propose that.

  According to the present invention described above, the strongest light component of the light guided in the optical fiber can be the incident angle θ in the Kretschmann arrangement described above, and the intensity of surface plasmon resonance absorption is large, so that sharp resonance An absorption spectrum can be obtained.

  Further, since the metal thin film that causes surface plasmon resonance is formed on the flat portion formed in the core of the optical fiber, it is easy to obtain a uniform film thickness.

  If the bent portion of the optical fiber and the vicinity thereof are covered with a light-shielding film except for the portion where the metal thin film is formed, the generation of surface plasmon resonance other than the flat portion where the metal thin film is formed can be suppressed. it can. For this reason, only the surface plasmon resonance in the plane portion is measured, and the resonance absorption spectrum can be prevented from becoming broad.

  In the present invention, the above-described optical fiber type surface plasmon resonance sensor is configured at a plurality of locations on the optical fiber from one end side where the light source unit is arranged to the other end side where the detection unit is arranged, thereby providing an optical fiber type surface plasmon resonance. A multi-channel sensor can be easily realized. This multi-channel configuration does not require complicated adjustment of the optical system, and the apparatus cost is low.

Next, the present invention will be described in detail with reference to the drawings showing embodiments.
FIG. 1 is a system diagram schematically showing an embodiment of an optical fiber type surface plasmon resonance sensor device to which the present invention is applied.
Reference numeral 1 denotes an optical fiber, and 2 denotes a sensor portion formed in the optical fiber 1. 2 or 3, the sensor unit 2 bends the optical fiber 1 to a predetermined angle θ satisfying the total reflection condition, and exposes at least the peak-side core 4 of the bent portion 3 from the clad 5. In this configuration, the flat portion 6 is formed, and a metal thin film 7 for generating surface plasmon resonance is formed on the flat portion 6.

  As shown in FIG. 2, the core 4 may be exposed from the clad 5 to form the metal thin film 7 as shown in FIG. 2, or as shown in FIG. Not only the portion 6 but also the bent portion 3 and its vicinity may be exposed from the clad 5.

  Further, as shown by a two-dot chain line in FIG. 3, the light-shielding film 8 made of a material such as a metal film, an organic film, or an inorganic film is formed on the bent portion 3 and the optical fiber 1 in the vicinity thereof except for a portion where a metal thin film is formed. It is preferable to cover with.

  Moreover, the metal thin film 7 formed in the plane part 6 can form appropriate metals, such as gold | metal | money, silver, copper, or aluminum, with a known film-forming method.

  In this way, a light source unit 9 for entering light is arranged on one end side of the optical fiber 1 on which the sensor unit 2 is formed, and detection is performed for detecting light passing through the sensor unit 2, that is, the bent portion 3 on the other end side. The optical fiber type surface plasmon resonance sensor device is configured by arranging the portion 10.

  In the figure, the light source unit 9 is composed of a light source 11 and a condenser lens 12, but the configuration of the light source unit 9 is appropriate. For example, the light source unit 9 can make white light incident on the optical fiber 1 and can also make infrared light or monochromatic light incident.

  In the figure, the detection unit 10 includes a light intensity detector 13 and a computer 14 that generates a resonance absorption spectrum from the light intensity detected by the detector 13. The detector 13 can be applied with an appropriate configuration for detecting the light intensity. For example, the detector 13 can be configured with a CCD element, a PD (photodiode) array, or the like via a spectroscope, a prism, or a grating.

  In the above configuration, light emitted from the light source 11, such as white light, infrared light, or monochromatic light, enters the optical fiber 1 through the condenser lens 12, propagates through the optical fiber 1, that is, the bent portion 3, that is, The sensor unit 2 is reached.

  The light reaching the sensor unit 2 passes through the bent portion 3 bent at a predetermined angle θ by being totally reflected by the plane portion 6. At this time, the surface plasmon is applied to the metal thin film 7 formed on the plane portion 6. Excited. It then propagates to the detector 13 where the light intensity is measured and a resonance absorption spectrum is generated by the computer 14.

  Since the sensor unit 2 is bent at an angle corresponding to the incident angle θ in the Kretschmann arrangement described above, the strongest light component of the light guided through the optical fiber is changed to the incident angle θ in the Kretschmann arrangement described above. Since the intensity of surface plasmon resonance absorption is large, a sharp resonance absorption spectrum can be obtained.

  Thus, in the present invention, by utilizing the surface plasmon resonance phenomenon, a slight change in the mass of the surface of the metal thin film 7 is changed to an incident angle at which a change in light intensity due to surface plasmon resonance absorption of the metal thin film 7 or surface plasmon resonance absorption occurs. A change in θ can be detected with high sensitivity.

  In the present invention, since the metal thin film 7 that causes surface plasmon resonance is formed on the flat portion 6 formed on the core 4 of the optical fiber 1, it is easy to obtain a uniform film thickness, thus enabling high-precision measurement. To do.

  And in this invention, if it is set as the structure which covered the bending part 3 and its vicinity of the optical fiber 1 with the light-shielding film | membrane 8 except the part in which the metal thin film 7 was formed, it will become except the plane part 6 in which the metal thin film 7 was formed. Therefore, only surface plasmon resonance at the plane portion 6 is measured, and the resonance absorption spectrum can be prevented from becoming broad.

A specific measuring method of the above apparatus will be described as follows.
First, white light is incident on the optical fiber 1 by the light source unit 9 to be guided, and the wavelength spectrum of the light transmitted through the sensor unit 2 is measured by the detection unit 10.

  Next, the wavelength portion of the transmitted light after the planar portion 6 of the core 4 on which the metal thin film 7 is formed is immersed in a reference solution is measured by the detection portion 10 and normalized to obtain a surface plasmon resonance absorption spectrum. The wavelength having the highest absorption rate is defined as the resonance wavelength.

  Next, the wavelength portion of the transmitted light after the planar portion 6 of the core 4 on which the metal thin film 7 is formed is immersed in the solution of the sample to be measured is measured by the detection portion 10 to obtain the surface plasmon resonance absorption spectrum and the most absorption. A change in refractive index can be detected by obtaining a high resonance wavelength and analyzing the difference from the resonance wavelength in the reference solution, and the change in mass of the sample can be measured from this.

  In addition, when the difference from the resonance wavelength described above is extremely small, a change in refractive index can be calculated from a change in light intensity at an arbitrary wavelength in the vicinity of the resonance wavelength, and a change in mass of the sample can be measured therefrom.

  As described above, the surface plasmon resonance sensor device is used for measurement intended for biochemical reaction as a main application. In this case, substances other than biochemical reaction are physically adsorbed on the sensor unit. Since the resonance absorption spectrum is also changed by factors such as the above, at least two channels of a sensor for detecting a target biochemical reaction and a reference sensor are required. The present invention can easily achieve this multi-channeling, and an example thereof will be described below.

  FIG. 4 is a system diagram schematically showing another embodiment of the optical fiber type surface plasmon resonance sensor device to which the present invention is applied. In this embodiment, in the apparatus shown in FIG. 1, the sensor units 2 (2a, 2b, 2c,...) Are arranged at a plurality of locations on the optical fiber 1 from one end side where the light source unit 9 is arranged to the other end side where the detection unit 10 is arranged. ), The same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The plurality of sensor portions 2 (2a, 2b, 2c,...) May be integrated with one optical fiber 1, or a plurality of optical fibers 1 as a single unit constituting the sensor portion 2 may be formed. It can also be connected and configured. In the latter case, a plurality of optical fibers 1 having sensor units 2 having different resonance wavelengths can be easily connected in series via a commercially available optical connector 15 or the like, and the number and selection of each resonance wavelength can be selected. In addition, it does not require complicated adjustment of the optical system, and the apparatus cost is low.

  As described above, the peak wavelength of surface plasmon resonance absorption is affected by the incident angle θ, the film type of the metal thin film 7 and the film thickness of the metal thin film 7, and therefore the sensor units 2 (2a, 2b, 2c) at the plurality of locations. ,... Are configured such that at least one of the angle θ of the bent portion 3, the material of the metal thin film 7, and the thickness of the metal thin film 7 is different.

  By configuring, for example, two sensor units 2 having different resonance wavelengths in the optical fiber 1 from the light source unit 9 to the detection unit 10, as shown in FIG. Two resonance absorption peaks corresponding to the above appear, and two channels can be measured by one light source unit 9 and one detection unit 10. Further, by configuring the three sensor units 2 in the optical fiber 1 extending from the light source unit 9 to the detection unit 10, as shown in FIG. 7, three corresponding resonance absorption peaks appear in the resonance absorption spectrum. Three channels can be measured by one light source unit 9 and detection unit 10.

FIG. 5 shows the angles θ (θ ₁ , θ ₂ , θ ₃ ,...) Of the bent portions 3 (3a, 3b, 3c,...) Of the sensor portions 2 (2a, 2b, 2c,. This shows an example in which the peak wavelength of resonance absorption is varied by changing.

Next, a procedure for detecting a biochemical reaction using a multi-channel optical fiber type surface plasmon resonance sensor device will be described.
First, a plurality of optical fibers 1 having sensor portions 2 having different resonance absorption wavelengths are connected in series by the optical connector 15 or the like. In these optical fibers 1, a biochemical substance that causes a biochemical reaction is planar. An optical fiber 1 that is disposed on the metal thin film 7 of the portion 6 and is surface-modified and an optical fiber 1 that is not surface-modified are used.

  When the biochemical substance whose surface has been modified on the metal thin film 7 has a component that specifically reacts in the sample, it reacts with this component to cause a minute mass on the metal thin film 7. This change in mass is detected as a change in the peak wavelength of resonance absorption in the corresponding channel. In this case, since physical adsorption or the like actually occurs at the same time, the change in the peak wavelength of resonance absorption occurring in the channel corresponding to the optical fiber having the sensor unit 2 that is not surface-modified is considered to be other than the biochemical reaction for detection. By analyzing the difference in wavelength change as a change due to the above factor, it is possible to determine the presence or absence of the target biochemical reaction and the presence or absence of a specific component.

  In the present invention, as described above, since the common light source unit 9 and the detection unit 10 can simultaneously measure a plurality of channels, all the resonance wavelength changes used are intermittently measured, for example, several times. By continuously measuring every 10 milliseconds, it is possible to obtain not only the presence or absence of the target component but also kinetic knowledge regarding the target biochemical reaction.

  As described above, the optical fiber type surface plasmon resonance sensor of the present invention bends the optical fiber at a predetermined angle that satisfies the total reflection condition, and exposes at least the mountain-side core of the bent portion from the clad to form a flat portion. At the same time, since the metal thin film for generating surface plasmon resonance is formed on the plane portion, there are many features as described below, and the industrial applicability is great.

1. The strongest light component of the light guided in the optical fiber can be the incident angle θ in the Kretschmann arrangement described above, and since the intensity of surface plasmon resonance absorption is large, a sharp resonance absorption spectrum can be obtained.
2. Since the metal thin film that causes surface plasmon resonance is formed on the flat surface formed in the core of the optical fiber, it is easy to obtain a uniform film thickness.
3. If the bent portion of the optical fiber and the vicinity thereof are covered with a light-shielding film except for the portion where the metal thin film is formed, the generation of surface plasmon resonance other than the flat portion where the metal thin film is formed can be suppressed. For this reason, only surface plasmon resonance at the plane portion is measured, and the resonance absorption spectrum can be prevented from becoming broad.
4). By configuring the above-described optical fiber type surface plasmon resonance sensor at a plurality of positions of the optical fiber from one end side where the light source unit is arranged to the other end side where the detection unit is arranged, the multi-channel of the optical fiber type surface plasmon resonance sensor Can be easily realized. This multi-channel configuration does not require complicated adjustment of the optical system, and the apparatus cost is low.

It is a systematic diagram showing an example of an optical fiber type surface plasmon resonance sensor device to which the present invention is applied typically. It is an enlarged view of an example of the sensor part of FIG. It is an enlarged view of the other example of the sensor part of FIG. It is a systematic diagram which shows typically the other Example of the optical fiber type surface plasmon resonance sensor apparatus to which this invention is applied. It is an enlarged view of an example of the sensor part of FIG. It is an example figure of the resonance absorption spectrum in the sensor part made multi-channel. It is another example figure of the resonance absorption spectrum in the sensor part made multi-channel. The conceptual diagram of operation | movement of a surface plasmon resonance sensor is shown. FIG. 6 is a correspondence diagram between an incident angle and reflectance indicating surface plasmon resonance absorption. It is a systematic diagram which shows an example of the conventional optical fiber type surface plasmon resonance sensor apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 (2a, 2b, 2c, ...) Sensor part 3 (3a, 3b, 3c, ...) Bending part 4 Core 5 Clad 6 Plane part 7 Metal thin film 8 Light-shielding film 9 Light source part 10 Detection part 11 Light source 12 Condenser lens 13 Detector 14 Computer 15 Optical connector

Claims (13)

An optical fiber is bent at a predetermined angle satisfying the total reflection condition, and at least a core on the peak side of the bent portion is exposed from the clad to form a flat portion, and a metal thin film for generating surface plasmon resonance in the flat portion is formed. Optical fiber type surface plasmon resonance sensor formed The optical fiber type surface plasmon resonance sensor according to claim 1, wherein the core has a metal thin film formed by exposing only a flat portion from the clad. The optical fiber type surface plasmon resonance sensor according to claim 1, wherein the core has a bent portion and its vicinity exposed from the clad. The optical fiber type surface plasmon resonance sensor according to any one of claims 1 to 3, wherein a bent portion of the optical fiber and its vicinity are covered with a light-shielding film except for a portion where a metal thin film is formed. 5. The optical fiber type surface plasmon resonance sensor according to claim 4, wherein the light shielding film is a metal film. 5. The optical fiber type surface plasmon resonance sensor according to claim 4, wherein the light shielding film is an organic film. 5. The optical fiber type surface plasmon resonance sensor according to claim 4, wherein the light shielding film is an inorganic film. A light source part for injecting white light is disposed on one end side of the optical fiber constituting the optical fiber type surface plasmon resonance sensor according to any one of claims 1 to 7, and the bent portion is disposed on the other end side. -Optic surface plasmon resonance sensor device having a detector for detecting light passing through A light source unit for injecting infrared light is disposed on one end side of the optical fiber constituting the optical fiber type surface plasmon resonance sensor according to any one of claims 1 to 7, and the bent portion is disposed on the other end side. An optical fiber type surface plasmon resonance sensor device provided with a detecting portion for detecting light passing through the portion While arranging the light source part which injects monochromatic light, such as a laser, in the one end side of the optical fiber which constitutes the optical fiber type surface plasmon resonance sensor according to any one of claims 1 to 7, on the other end side, An optical fiber type surface plasmon resonance sensor device provided with a detecting portion for detecting light passing through the bent portion. The optical fiber type surface plasmon resonance sensor according to any one of claims 1 to 7, wherein the optical fiber surface plasmon resonance sensor according to any one of claims 1 to 7 is formed at a plurality of positions of an optical fiber extending from one end side where the light source unit is arranged to the other end side where the detection unit is arranged. The optical fiber type surface plasmon resonance sensor device according to 8, 9 or 10 12. The optical fiber type surface plasmon resonance sensor device according to claim 11, wherein the optical fiber type surface plasmon resonance sensor configured at a plurality of locations is configured by connecting a plurality of single optical fiber type surface plasmon resonance sensors in series. 12. The light according to claim 11, wherein the optical fiber type surface plasmon resonance sensor configured at a plurality of positions is configured such that at least one of an angle of the bent portion, a material of the metal thin film, and a thickness of the metal thin film is different. Fiber type surface plasmon resonance sensor device

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