JP2009139669A - Optical device - Google Patents

Abstract

An optical characteristic that can only be realized by an optical element having a three-dimensional structure that is difficult to manufacture is realized by a simple two-dimensional structure.
A first light conversion element having an output surface 23 parallel to an input surface 22 in which an exit position 9 corresponds one-to-one with respect to an incident angle 8 and an incident direction of light 6 incident from the input surface 22. 1 is disposed in the vicinity of the output surface 23, is homogeneous in the direction perpendicular to the output surface 23 of the first light conversion element 1, and has optical characteristics at the incident position 9 corresponding to the emission position 9 on the output surface 23. The optical element 2 having the same optical characteristics according to the incident angle 8 and the incident direction, and the optical element 2 are arranged close to the optical element 2 so that the light emitted from the optical element 2 is incident, and the incident position 21 of the light Are provided in order from the incident side of the light.
[Selection] Figure 1

Description

  The present invention relates to an optical device having high dispersion characteristics. For example, the present invention relates to a light receiving device having high dispersion characteristics realized by a photonic crystal having a three-dimensional structure.

  In order to realize a super collimator and a photonic band gap, optical characteristics that cannot be realized by a naturally existing material are required, and thus these cannot be realized by conventional optical components.

  However, it has been found that a super collimator and a photonic band gap can be realized by using a crystal structure such as an artificially produced photonic crystal having high dispersion characteristics.

  Therefore, recently, a technique for producing an artificial crystal structure such as a photonic crystal has been developed.

  As a technique for producing a photonic crystal having a three-dimensional structure, for example, a light beam obtained by dividing one laser beam into a plurality of angles is irradiated into the photosensitive resin layer at an angle, and the photosensitive resin layer is irradiated with the laser by three-dimensional interference. A device that forms an image corresponding to a photonic crystal structure has been proposed (for example, see Patent Document 1).

  In addition, two or more kinds of materials having different refractive indexes are alternately and periodically laminated on a substrate on which a two-dimensional periodic pattern is formed, and then a two-dimensional vertical periodic structure is processed perpendicularly to the periodic direction. Has also been proposed (see, for example, Patent Document 2).

In addition, a structure in which a periodic structure is formed by laminating fine particles on an inclined end face of an optical fiber has been proposed (see, for example, Patent Document 3).
JP 2000-329920 A (for example, FIG. 1) Japanese Patent Laid-Open No. 2001-74954 (for example, FIG. 16) JP 2004-264872 A (for example, FIG. 3)

  However, when a super collimator or a photonic band gap is realized using a conventional method for producing a photonic crystal having a three-dimensional structure, the process is complicated and expensive.

  In other words, the conventional manufacturing method of Patent Document 1 requires a three-dimensional interference, so that the optical system is complicated.

  In addition, since the manufacturing method of Patent Document 2 is a three-dimensional process in which one dimension is further added to the two-dimensional structure, the process is complicated.

  The manufacturing method of Patent Document 3 is simple because the crystal grows naturally. However, since the structure that can be manufactured is limited to the close-packed structure, a photonic liquid crystal having desired optical characteristics is manufactured. I can't.

  In this way, the fabrication of crystal structures such as supercollimators and photonic crystals with a three-dimensional structure that can realize photonic band gaps may not be possible with the current general-purpose two-dimensional stacking process. Even if it was possible, the process was complicated and expensive.

  In view of the above-described conventional problems, an object of the present invention is to provide an optical device having a simple structure and a high dispersion characteristic capable of realizing a super collimating function.

  Another object of the present invention is to provide an optical device having a high dispersion characteristic capable of obtaining a photonic band gap effect with a simple structure in consideration of the above-described conventional problems.

In order to solve the above-described problem, the first aspect of the present invention provides:
A first light conversion element having an output surface parallel to the input surface, the output position corresponding to the incident direction of light incident from the input surface in a one-to-one relationship;
The optical characteristic at the incident position corresponding to the exit position is uniform in the direction perpendicular to the output face of the first light conversion element, arranged close to the output face, and according to the incident direction. An optical element corresponding to
A second light conversion element that is arranged in the vicinity of the optical element so that the light emitted from the optical element is incident thereon, and that outputs in the emission direction corresponding to the incident position of the light in a one-to-one relationship; These optical devices are provided in order from the incident side.

The second aspect of the present invention provides
The relationship between the incident position and the exit position of light incident on the optical element from a predetermined position is such that the direction of the straight line connecting the incident position and the exit position is parallel to the direction perpendicular to the output surface. The optical device according to the first aspect of the present invention.

The third aspect of the present invention
The first light conversion element and the second light conversion element are a refractive index distribution type lens having a refractive index distribution that decreases in a parabolic manner according to a distance from the central axis at a maximum on a central axis. It is an optical device of the invention.

The fourth aspect of the present invention is
By setting the refractive index of the optical element to be a refractive index that decreases according to the distance from the central axis, the light diffused with respect to the input light incident on the first light conversion element in a predetermined incident angle range can be obtained. It is the optical device of 3rd this invention output from a 2 light conversion element.

The fifth aspect of the present invention provides
By setting the refractive index of the optical element to be a refractive index that increases according to the distance from the central axis, parallel light or condensed light with respect to input light incident on the first light conversion element in a predetermined incident angle range. Is an optical device according to the third aspect of the present invention.

The sixth aspect of the present invention provides
The optical element according to the third aspect of the present invention has a structure in which a plurality of optical objects are arranged in a two-dimensional direction perpendicular to the central axis.

The seventh aspect of the present invention
In the optical device according to the sixth aspect of the present invention, the refractive indexes of the optical objects are different.

In addition, the eighth aspect of the present invention
The refractive index of each optical object can be changed by electrical control,
Controlling an output from the second light conversion element by controlling a relationship between a refractive index of each optical object, a distance of each optical object from the central axis, and a rotation angle around the central axis; This is an optical device of the present invention.

The ninth aspect of the present invention provides
In the optical device according to the seventh aspect of the invention, the relationship between the refractive index of each optical object and the distance from the central axis is made different according to the rotation angle around the central axis.

The tenth aspect of the present invention is
Regarding the rotation angle around the central axis, the relationship between the refractive index of each optical object and the distance from the central axis has a rotation angle range in which the correlation is negative and a rotation angle range in which the correlation is positive. It is an optical device of the ninth aspect of the present invention.

The eleventh aspect of the present invention is
A direction perpendicular to the input surface of the light incident from the input surface, the output surface having an output surface parallel to the input surface corresponding to the incident direction of the light incident from the input surface. A first light conversion element that reduces an exit angle at an exit position on the exit surface with respect to an incident angle with respect to
An optical device comprising: a photonic crystal that is disposed in the vicinity of the output surface and has a periodic structure in a direction perpendicular to the input surface of the first light conversion element.

The twelfth aspect of the present invention is
The period of the periodic structure of the photonic crystal is the optical device according to the eleventh aspect of the present invention, wherein the period of the predetermined light incident from the first light conversion element is substantially equal to an integral multiple of a half wavelength.

The thirteenth aspect of the present invention is
It is arranged close to the photonic crystal so that light having a wavelength other than the wavelength of the predetermined light emitted from the photonic crystal is incident, and has a one-to-one correspondence with the incident position of the light. An optical device according to a twelfth aspect of the present invention, comprising the second optical conversion element that outputs in the emission direction.

The fourteenth aspect of the present invention is
The thirteenth book, wherein the first light conversion element and the second light conversion element are refractive index distribution type lenses having a refractive index distribution that decreases in a parabolic manner according to the distance from the central axis at a maximum on the central axis. It is an optical device of the invention.

The fifteenth aspect of the present invention provides
The first light conversion element is a gradient index lens having an optical path length of 0.25 + 0.5 × i pitch (i is an integer of 0 or more);
In the optical device according to the third or fourteenth aspect of the present invention, the second light conversion element is a gradient index lens having an optical path length of 0.25 + 0.5 × j pitch (j is an integer of 0 or more). is there.

  According to the present invention, it is possible to provide an optical device having a high dispersion characteristic capable of realizing a super collimating function with a simple structure.

  According to another aspect of the present invention, it is possible to provide an optical device having a high dispersion characteristic capable of obtaining a photonic band gap effect with a simple structure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a schematic side sectional view of an optical device according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the optical device according to the first embodiment includes, in order from the light incident side, an input side 0.25 pitch gradient index (GRIN) lens 1, a two-dimensional array optical element 2, and an output side. It is composed of a 0.75 pitch GRIN lens 3.

  The input side 0.25 pitch gradient index (GRIN) lens 1, the two-dimensional array optical element 2, and the output side 0.75 pitch GRIN lens 3 are the first light conversion element and the optical element of the present invention, respectively. And an example of the second light conversion element.

  The input-side 0.25 pitch GRIN lens 1 is a GRIN lens having a refractive index distribution that is maximum at the central axis 5 and decreases in a parabolic manner according to the distance from the central axis 5, and has an optical path length of 0.25 pitch. .

  The two-dimensional array optical element 2 has a thin film shape, and is disposed close to the output surface 23 of the input side 0.25 pitch GRIN lens 1. The two-dimensional array optical element 2 is homogeneous in the direction of the central axis 5 (film thickness direction), and the i-th material 4 (i = 1, 2, 3,...) In the two-dimensional direction perpendicular to the central axis 5. , M: m is an integer).

  The plurality of i-th materials 4 constituting the two-dimensional array optical element 2 correspond to an example of a plurality of optical objects of the present invention.

  When the input side 0.25 pitch GRIN lens 1 is assumed to be incident with light traveling in the direction along the paper surface shown in FIG. 1, the incident angle θi8 is incident on the input side 0.25 pitch GRIN lens 1. The light incident at (i = 1, 2, 3,..., M: integer) is emitted from an emission position on the output surface 23 that has a one-to-one correspondence with the incident angle θi8. Therefore, the light enters the two-dimensional array optical element 2 at the material incident position ri9 corresponding to the emission position on the output surface 23, which corresponds to the incident angle θi8 on a one-to-one basis. The optical characteristics (refractive index) of the i-th material 4 arranged at the material incident position ri9 are equal to the desired three-dimensional dispersion characteristics (frequency ωi, refractive index at the incident angle θi is equal to ni). i materials 4 are arranged.

  In the above description, in order to make the explanation easy to understand, the input side 0.25 pitch GRIN lens 1 has been described as being incident with light traveling in the direction along the paper surface illustrated in FIG. The incident light 6 also enters the input surface 22 from the direction (left front of the paper, left rear of the paper, etc.). These incident lights 6 are emitted from the emission positions on the output surface 23 corresponding to the incident direction on a one-to-one basis. That is, the light enters the material incident position ri9 of the two-dimensional array optical element 2 corresponding to the output position on the output surface 23, which corresponds to the incident direction on the input surface 22 on a one-to-one basis. The optical characteristic (refractive index) of the i-th material 4 arranged at the material incident position ri9 is equal to a desired three-dimensional dispersion characteristic (frequency ωi, refractive index in the direction of incidence on the input surface 22 is ni). The i-th materials 4 are arranged in a two-dimensional direction perpendicular to the central axis 5.

  The “desired three-dimensional dispersion characteristic” in this specification is, for example, a characteristic having a dispersion surface related to the incident direction as shown in FIG. 2C or FIG. 4C. Details of these dispersion surfaces will be described later.

  The output side 0.75 pitch GRIN lens 3 having a refractive index distribution which is maximum at the central axis 5 and decreases in a parabolic manner according to the distance from the central axis 5 and which has an optical path length of 0.75 pitch, It is arranged close to the two-dimensional array optical element 2 so that the axis coincides with the central axis 5 of the input side 0.25 pitch gradient index (GRIN) lens 1.

  Note that the input side 0.25 pitch GRIN lens 1 and the two-dimensional array optical element 2, the two-dimensional array optical element 2 and the output side 0.75 pitch GRIN lens 3 may be in contact with each other, or may be disposed apart from each other. May be.

  The incident angle in this specification refers to a straight line parallel to the central axis 5 on a plane formed by a straight line passing through an incident position parallel to the central axis 5 of the optical device and a light path of incident light. The angle formed by the ray path of incident light. Similarly, the exit angle in this specification refers to a straight line parallel to the central axis 5 on a plane formed by a straight line passing through an output position parallel to the central axis 5 of the optical device and a light beam path of the emitted light. And the angle formed by the beam path of the emitted light. Therefore, the incident angle θi8 and the outgoing angle θo20 shown in FIG. 1 are the incident angle and the outgoing angle referred to in this specification.

  In FIG. 1, the path of light incident on the optical device according to the first embodiment is schematically shown by a solid line, a dotted line, a broken line, and a long broken line for each light incident at a different incident angle θi8. Since the phase velocity and the group velocity are different after passing through the two-dimensional array optical element 2, the wave number locus is shown in the output side 0.75 pitch GRIN lens 3, and the output side 0.75 pitch GRIN lens 3 is shown. The outgoing light 7 emitted from the output surface 25 is indicated by an intuitive light beam (group velocity). The reason for indicating the light path in this way will be described later.

  Next, a mechanism for obtaining optical three-dimensional characteristics using a two-dimensional structure will be described with reference to FIGS.

  2A shows the dispersion characteristics of each i-th material 4 of the two-dimensional array optical element 2, and FIG. 2B shows the dispersion surface of each i-th material 4 of the two-dimensional array optical element 2. FIG. Yes. FIG. 2C shows a dispersion surface when the number m of each i-th material 4 of the two-dimensional array optical element 2 is increased.

  FIG. 3 schematically shows a light path when collimated light is incident on the optical device of the first embodiment shown in FIG. 1 as incident light 6. 3A is a schematic diagram when incident light 6 is incident at an incident angle θi = 0 °, and FIG. 3B is a schematic diagram when incident light 6 is incident at an incident angle θi> 0 °. Respectively.

  First, as shown in FIGS. 3A and 3B, incident light 6 incident on the input surface 22 of the incident side 0.25 pitch GRIN lens 1 at an incident angle θi is at an incident position on the input surface 22. Regardless, the light is condensed at the same emission position on the output surface 23.

  The light emitted from the incident side 0.25 pitch GRIN lens 1 collected on the output surface 23 is uniformly refracted in the direction of the central axis 5 constituting the two-dimensional array optical element 2 arranged close to the output surface 23. After interacting with the i-th material 4 having the rate ni, the light enters the incident position on the input surface 24 of the output-side 0.75 pitch GRIN lens 3 and exits from the output surface 25 at the exit angle θo.

  However, the optical path length of the two-dimensional array optical element 2 is less than or equal to the focal range of the 0.25 pitch GRIN lens 1, and the incident position on the two-dimensional array optical element 2 with reference to the central axis 5 is approximately two-dimensional. It is designed to be equal to the emission position of the array optical element 2. That is, the straight line connecting the incident position and the emitting position on the two-dimensional array optical element 2 can be regarded as being parallel to the central axis 5, and the incident angle on the two-dimensional array optical element 2 is determined from the two-dimensional array optical element 2. It is designed to be equal to the emission angle. Specifically, these conditions are satisfied by designing the film thickness t of the two-dimensional array optical element 2 to be very thin with respect to the optical path length L of the optical device of the first embodiment. it can.

  In FIG. 2A, the dispersion characteristics of each i-th material 4 constituting the two-dimensional array optical element 2 are shown in accordance with the shape of a line indicating the path of light incident on each i-th material 4 in FIG. ing. That is, in FIG. 1, the dispersion characteristics of each i-th material 4 on which the respective light beams indicated by the solid line, the dotted line, the broken line, and the long broken line are incident are shown in FIG. Respectively.

  When the refractive index (the reciprocal of the gradient of the dispersion relationship) of the i-th material 4 constituting the two-dimensional array optical element 2 is decreased according to the distance from the central axis 5 as shown in FIG. 2A, the dispersion surface at the frequency ω1. As shown in FIG. 2B, the wave number decreases stepwise from the direction of the central axis 5 (propagation direction kz) to the direction (kx) perpendicular to the central axis 5 (as the incident angle θi increases).

  Then, the number m of the i-th material 4 is set so that the change in the refractive index in the two-dimensional direction perpendicular to the central axis 5 of the two-dimensional array optical element 2 composed of the i-th material 4 having a different refractive index becomes smooth. When the value is increased, the dispersion surface 26 becomes smooth as shown in FIG. 2C. Therefore, the incident angle θi8 (incident direction) of the incident side 0.25 pitch GRIN lens 1 and the output of the incident side 0.25 pitch GRIN lens 1 are obtained. If the relationship between the refractive index ni of the i-th material 4 constituting the two-dimensional array optical element 2 positioned at the position ri9 is equal to the relationship between the desired incident angle θ (incident direction) and the refractive index n (θ), Dispersion characteristics equivalent to the desired three-dimensional structure dispersion characteristics (incident angle (incident direction) and refractive relationship) can be obtained with the two-dimensional structure.

  In this way, the beam conversion unit (incident side 0.25 pitch GRIN lens 1 and output side 0.75 pitch GRIN lens 3) that converts angle information into position information and a desired three-dimensional angular characteristic (dispersion relationship) are provided. By arranging the material (i-th material 4) in a two-dimensional direction perpendicular to the optical axis, an optical three-dimensional characteristic can be realized using a two-dimensional structure.

  If the pitch of the output side 0.75 pitch GRIN lens 3 is also set to 0.25, outgoing light having a direction symmetrical to the central axis 5 with respect to the incident light θi8 can be obtained, so that the refractive index with respect to the incident angle θi8. It is equivalent to -ni and shows the negative refraction characteristics of the desired material.

  FIG. 4A shows the dispersion characteristics of the two-dimensional array optical element 2 when the i-th materials 4 are arranged so that the refractive index increases according to the distance from the central axis. FIG. 4B shows a dispersion surface of the two-dimensional array optical element 2 when the i-th materials 4 are arranged so as to have the dispersion characteristics shown in FIG. FIG. 4C shows a flat dispersion surface and negative curvature when the number i of each i-th material 4 is increased in an arrangement in which each i-th material 4 increases in refractive index according to the distance from the central axis. The example of the dispersion surface of a radius is shown.

  Contrary to the relationship shown in FIG. 2 (a), the refractive index of the i-th material 4 constituting the two-dimensional array optical element 2 (reciprocal of the slope of the dispersion relationship) is the central axis as shown in FIG. 4 (a). When the distance is increased according to the distance from 5, the dispersion surface at the frequency ω1 is changed from the direction of the central axis 5 (propagation direction kz) to the direction (kx) perpendicular to the central axis 5 (incident angle θi) as shown in FIG. The wave number increases stepwise as the value increases.

  Then, the number m of the i-th material 4 is set so that the change in the refractive index in the two-dimensional direction perpendicular to the central axis 5 of the two-dimensional array optical element 2 composed of the i-th material 4 having a different refractive index becomes smooth. 4C, the dispersive surface of the two-dimensional array optical element 2 is changed to a parallel light dispersive surface 27 that is flat in the kz direction, or a condensing dispersive surface 28 that draws an arc having a negative curvature radius. Can be.

  When the dispersion surface is a positive curvature radius as shown in FIG. 2 (c), light diffuses like a natural material, but in the case of a flat surface (parallel light dispersion surface 27) as shown in FIG. 4 (c). Regardless of the incident state, it becomes parallel light (super collimator), or when the radius of curvature is negative (condensation dispersion surface 28), it becomes condensed light.

  Furthermore, the mechanism by which high dispersion characteristics can be obtained by the optical device having the configuration of the first embodiment will be described in detail with reference to FIG.

  FIG. 5A is a diagram for explaining a dispersion surface when diffuse light is output by the optical device according to the first embodiment. FIGS. 5B and 5C show diagrams in the case where parallel light and condensed light are output by the optical device according to the first embodiment, respectively. The dispersion surface of the GRIN lens which comprises the optical device, and a two-dimensional arrangement | sequence optical element is shown.

  The dispersion surface of the GRIN lens shown in FIG. 5A is the dispersion surface of the input side 0.25 pitch GRIN lens 1 and the output side 0.75 pitch GRIN lens 3 shown in FIG. 1, and is a concentric dotted line. The radius decreases as the distance from the central axis increases. Further, the curve indicated by the solid line outside the dispersion surface of the GRIN lens represents the dispersion surface of the two-dimensional array optical element.

  First, the spatial vibration state (wave number k) of propagating light will be described for diffused light.

  In FIG. 5A, three types of incident light having different incident angles are indicated by a dotted line, a broken line, and a long broken line.

  These incident lights having different incident angles propagate with different propagation constants (cosine of the kz axis). In FIG. 5A, the propagation constant of the incident light with a long broken line is indicated by a thick dotted line (on the kz axis). In the case of incident light indicated by a long broken line, the ray trajectory moves on the alternate long and short dash line shown in FIG. 5A according to the pitch passing through the GRIN lens.

  At this time, the propagation constant kz is constant (the momentum conservation law in the z direction), but only kx varies and returns to the original with one pitch. Here, when a two-dimensional array optical element is disposed at a pitch of 0.25 (kx = 0), kx = 0 is stored on the input / output side boundary surface by the momentum conservation law in the x direction. The array optical element only serves to add a constant phase difference in the kz direction, and the subsequent change in the wave number k in the 0.75 pitch GRIN lens changes in the same manner as when there is no two-dimensional array optical element. . Therefore, the wave number k at the exit end of the 0.75 pitch GRIN lens is the same as the wave number k at the entrance end of the 0.25 pitch GRIN lens.

  In the case of a configuration with only a GRIN lens without a two-dimensional array optical element, the dispersion planes are all concentric circles, and the phase velocity and group velocity are the same, so the trajectory of wave number k and the ray trajectory are the same.

  On the other hand, when a two-dimensional array optical element having a dispersive surface different from the concentric circle is added, the change in phase velocity is the same, but the change in phase applied in the z direction is different at the incident angle. That is, in this case, the trajectory of the wave number k is the same regardless of the presence or absence of the two-dimensional array optical element, but the trajectory of the light beam (group velocity) is different.

  Therefore, in the output-side 0.75 pitch GRIN lens 3 of the optical device according to the first embodiment shown in FIG. 1, the trajectory of wave number k and the trajectory of light rays (group velocity) are different. Therefore, in FIG. 1, a locus of wave number k is drawn in the output side 0.75 pitch GRIN lens 3, and the emitted light 7 emitted from the output surface 25 of the output side 0.75 pitch GRIN lens 3 is intuitive. Draws a ray (group velocity).

  Since the propagation constant kx returns to the original at one pitch, the phase change on the input surface 22 of the input side 0.25 pitch GRIN lens 1 and the output surface 25 of the output side 0.75 pitch GRIN lens 3 is substantially two-dimensionally arranged. This is only the contribution of the optical element 2. Therefore, the state of the output side 0.75 pitch GRIN lens 3 on the output surface 25 is the i-th refractive index ni arranged at the material incident position ri9 of the two-dimensional array optical element 2 corresponding to the incident angle θi8. Equivalent to material 4.

  Therefore, in the optical device according to the first embodiment shown in FIG. 1, when the two-dimensional array optical element 2 having the dispersion surface as shown in FIG. 5A is used, the dispersion surface as shown in FIG. 26 can be formed, and diffused light can be emitted.

  Similarly, when the two-dimensional array optical element 2 having a dispersion surface as shown in FIG. 5B is used, the parallel light dispersion surface 27 shown in FIG. 4C can be formed, and the parallel light is emitted regardless of the incident angle. Can be made.

  Similarly, when the two-dimensional array optical element 2 having a dispersion surface as shown in FIG. 5C is used, the light collection and dispersion surface 28 shown in FIG. 4C can be formed, and the light is collected after being emitted from the optical device. Condensed light can be emitted.

  FIG. 6A shows a schematic light path of the optical device according to the first embodiment using a two-dimensional array optical element having a dispersion surface approximate to the parallel light dispersion surface 27 as the two-dimensional array optical element 2. FIG. 6B shows a schematic light path of the optical device of the first embodiment using a two-dimensional array optical element having a dispersion surface that approximates the condensing dispersion surface 28.

  6A and 6B, similarly to FIG. 1, a locus of the wave number k is drawn in the output side 0.75 pitch GRIN lens 3 and is emitted from the output surface 25 of the output side 0.75 pitch GRIN lens 3. The emitted light 7 thus drawn depicts an intuitive light beam (group velocity). As described above, since the wave number k does not change even if the dispersion surfaces of the two-dimensional array optical element 2 are different, the locus of the wave number k in the output-side 0.75 pitch GRIN lens 3 in FIGS. 6 (a) and 6 (b). Is a locus similar to the locus of the wave number k in the output side 0.75 pitch GRIN lens 3 of the optical device shown in FIG.

  In the case of FIG. 6A, since the two-dimensional array optical element 2 has a dispersion surface that approximates the parallel light dispersion surface 27, it is positioned at the position of the central axis 5 on the input surface 22 of the input side 0.25 pitch GRIN lens 1. Regardless of the incident angle, the incident light 6 that has entered is emitted as the outgoing light 7 along the central axis 5. Similarly, light incident on another position on the input surface 22 is emitted in parallel with the central axis 5 from another position on the output surface 25 regardless of the incident angle. Therefore, incident light 6 incident on the input surface 22 at various angles is emitted as parallel light parallel to the central axis 5 from the output surface 25.

  Even if a photonic crystal having a complicated three-dimensional structure is not produced as in the prior art, a super collimator can be realized by producing a two-dimensional structure like the optical device of the first embodiment.

  In the case of FIG. 6B, since the two-dimensional array optical element 2 has a dispersion surface that approximates the condensing dispersion surface 28, it is positioned at the position of the central axis 5 on the input surface 22 of the input side 0.25 pitch GRIN lens 1. Incident incident light 6 is emitted from the position of the central axis 5 as outgoing light 7 at an outgoing angle different from the incident angle with respect to the incident angle. FIG. 6B shows a locus of light incident at a different incident angle on the position of the central axis 5 on the input surface 22. However, when parallel light is incident on the input surface 22, the input surface 22 is input. The emission angle of the light emitted from the output surface 25 differs depending on the upper incident position, and becomes the emitted light 7 that is collected from the optical device after being emitted from the output surface 25.

  In FIG. 6B, since the two-dimensional array optical element 2 has a dispersion surface that approximates the condensing dispersion surface 28, the incident light 6 is incident as shown in FIG. Outgoing light 7 is emitted in a direction opposite to the corner, that is, in a direction having a negative refractive index.

  In the above, for the sake of easy understanding, the refractive index change of the two-dimensional array optical element 2 has been described as being concentric, ie, one-dimensional, but the refractive index change is also provided in the rotational direction of the central axis 5. Also good.

  FIG. 7A shows a cross-sectional configuration diagram of the two-dimensional array optical element 2 in which the refractive index is changed in the rotation direction of the central axis 5. FIG. 7B shows the dispersion characteristics of the two-dimensional array optical element 2 having a refractive index change as shown in FIG.

  In the two-dimensional array optical element 2 shown in FIG. 7A, the diffused light portion 11, the parallel light portion 12, and the condensed light portion 13 have different refractive indexes even in the portion indicated by the same pattern. As described above, when the refractive index is changed in the central axis rotation direction (incident angle azimuth βi10) in the two-dimensional array optical element 2, a different dispersion surface can be realized in the incident angle azimuth βi. Hybrid optical characteristics combining the light portion 13 and the parallel light portion 12 can also be realized.

  That is, the dispersion of the condensed light portion 13 so that the dispersion surface of the diffusion light portion 11 becomes the diffusion dispersion surface 29 of FIG. 7B and the dispersion surface of the parallel light portion 12 becomes the parallel light dispersion surface 30. By arranging the i-th material 4 of the two-dimensional array optical element 2 so that the surface becomes the condensing dispersion surface 31, the radius of curvature is positive (diffuse dispersion surface) or negative (condensation dispersion surface) depending on the material incident position ri9. Surface) and flat (parallel light dispersion surface) can be provided with different optical characteristics.

  Note that the angle range in which the incident angle azimuth βi10 of FIG. 7A becomes the diffused light portion 11 is a rotation angle in which the relationship between the refractive index of each optical object and the distance from the central axis has a negative correlation in the present invention. As an example of the range, the angle range in which the incident angle direction βi10 becomes the parallel light portion 12 and the condensed light portion 13 indicates that the relationship between the refractive index of each optical object and the distance from the central axis of the present invention is a positive correlation. This is an example of the rotation angle range.

  When the optical device of the first embodiment having such hybrid optical characteristics is used, the beam shape can be arbitrarily controlled. For example, by arranging them so that they are “parallel light parts” in the x direction and “condensed light parts” in the y direction, a linear beam shape that collects parallel light in the x direction and in the y direction is realized. it can.

  In the first embodiment, the optical path length of the input side 0.25 pitch GRIN lens 1 is 0.25 pitch, but the optical path length is 0.25 + 0.5 × i pitch (i is an integer of 0 or more). The same effect can be obtained. Similarly, although the optical path length of the output side 0.75 pitch GRIN lens 3 is 0.75 pitch, the optical path length may be 0.25 + 0.5 × j pitch (j is an integer of 0 or more).

  In the first embodiment, the case where the refractive index of the i-th material 4 of the two-dimensional array optical element 2 is positive has been described, but the refractive index may be negative.

  Any material may be used as the i-th material 4 constituting the two-dimensional array optical element 2 of Embodiment 1 as long as it is a substance having i types of refractive indexes.

  For example, polymerization of 2,2-bi (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and pyromellitic dianhydride can be used as a method for changing the refractive index of i types in each i-th material 4. By mixing the product and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl and changing the fluorine content in the mixture, i types of refractive indices can be realized.

  Further, i types of refractive indexes can be realized even if the composition ratio of the compound semiconductor is changed.

  Further, as the i-th material 4, a substance such as liquid crystal that has an electrically changing refractive index is used, and the optical characteristics are changed by one optical device by controlling the electrically changing refractive index. Also good.

(Embodiment 2)
FIG. 8 is a schematic side sectional view of the optical device according to the second embodiment of the present invention. In addition, the same code | symbol is used for the same component as FIG.

  As shown in FIG. 8, the optical device according to the second embodiment includes an input side 0.25 pitch gradient index (GRIN) lens 1, a one-dimensional photonic crystal 14, and an output side in order from the light incident side. It is composed of a 0.75 pitch GRIN lens 3.

  The input side 0.25 pitch gradient index (GRIN) lens 1 and the output side 0.75 pitch GRIN lens 3 are examples of the first light conversion element and the second light conversion element of the present invention, respectively. The one-dimensional photonic crystal 14 corresponds to an example of a photonic crystal having a periodic structure in a direction perpendicular to the input surface of the first light conversion element of the present invention.

  The input-side 0.25 pitch GRIN lens 1 is a GRIN lens having a refractive index distribution that is maximum at the central axis 5 and decreases in a parabolic manner according to the distance from the central axis 5, and has an optical path length of 0.25 pitch. .

  Further, the output side 0.75 pitch GRIN lens 3 having a refractive index distribution which is maximum at the central axis 5 and decreases in a parabolic manner according to the distance from the central axis 5 and which has an optical path length of 0.75 pitch is provided at the center. The optical axis is arranged close to the one-dimensional photonic crystal 14 so as to coincide with the central axis 5 of the input side 0.25 pitch gradient index (GRIN) lens 1.

  The configurations of the input side 0.25 pitch GRIN lens 1 and the output side 0.75 pitch GRIN lens 3 are the same as the configurations of the GRIN lenses of the optical device according to the first embodiment shown in FIG.

  The thickness of the one-dimensional photonic crystal 14 is such that the optical path length is substantially an integral multiple of a half wavelength of light for obtaining a photonic band gap. Here, “substantially” an integral multiple of a half wavelength is not limited to an integral multiple of a half wavelength, but includes a range where the effect of a photonic bandgap can be obtained. Thickness that can be equated with double.

  In other words, the configuration of the optical device according to the second embodiment is such that all the homogeneous materials in the direction of the central axis 5 constituting the two-dimensional array optical element 2 of the optical device according to the first embodiment shown in FIG. In this configuration, a one-dimensional photonic crystal 14 having a one-dimensional refractive index period in the direction is replaced.

  The input-side 0.25 pitch GRIN lens 1 and the one-dimensional photonic crystal 14, and the one-dimensional photonic crystal 14 and the output-side 0.75 pitch GRIN lens 3 may be in contact with each other or arranged separately. May be.

  9A shows the dispersion characteristics of the one-dimensional photonic crystal 14, and FIG. 9B shows the dispersion surface of the one-dimensional photonic crystal 14 at the frequency ω1.

  As shown in FIG. 9A, when the dispersion characteristic 32 of the one-dimensional photonic crystal 14 has the photonic band gap 15 at the light source frequency ω1, the dispersion surface of the frequency ω1 is as shown in FIG. 9B. There is no dispersion curve. That is, since the Bragg reflection is performed regardless of the incident angle, a full band gap can be realized. However, precisely, since the light receiving angle of the input side 0.25 pitch GRIN lens 1 is limited, a band gap can be obtained in the light receiving angle range of the input side 0.25 pitch GRIN lens 1.

  In order to obtain the effect of the photonic band gap with the one-dimensional photonic crystal 14 alone, light must be incident perpendicularly to the input surface of the one-dimensional photonic crystal 14, that is, within a limited narrow angle range. In the optical device of the second embodiment, incident light 6 incident on the input surface 22 by the input side 0.25 pitch GRIN lens 1 in a wide angle range is incident on the incident surface of the one-dimensional photonic crystal 14 perpendicularly. Thus, since the direction of the incident light 6 is controlled, the effect of the photonic band gap can be obtained for light incident from a wide angle range. Further, the output side 0.75 pitch GRIN lens 3 converts the direction of the light emitted from the one-dimensional photonic crystal 14 into the emission direction of the optical device of the second embodiment, and emits it.

  That is, by using the configuration of the optical device according to the second embodiment, the one-dimensional photonic crystal 14 is used to obtain optical characteristics such as a full band gap that can be obtained only with a two-dimensional or three-dimensional photonic crystal. realizable.

  As described above, when a desired characteristic does not change with an incident angle like a band gap, a three-dimensional characteristic can be realized with a one-dimensional configuration.

  For example, an optical filter that blocks only light of a specific frequency can be realized by using the optical device according to the second embodiment.

  When the desired dispersion characteristic is not a full band gap but the band gap and the refractive index are changed at the incident angle, the period is different in a two-dimensional direction perpendicular to the central axis 5 instead of the one-dimensional photonic crystal 14. A photonic crystal may be used.

  In the second embodiment, the optical path length of the input side 0.25 pitch GRIN lens 1 is 0.25 pitch, but the optical path length is 0.25 + 0.5 × i pitch (i is an integer of 0 or more). The same effect can be obtained. Similarly, although the optical path length of the output side 0.75 pitch GRIN lens 3 is 0.75 pitch, the optical path length may be 0.25 + 0.5 × j pitch (j is an integer of 0 or more).

  As described above, the optical device of the present invention can obtain the dispersion characteristics of a three-dimensional structure equivalently with a lower-dimensional structure in a three-dimensional structure that is difficult to manufacture.

  That is, according to the present invention, a structure having one dimension lower than the desired dimension, for example, when the desired structure is a three-dimensional structure, optically equivalent characteristics to the three-dimensional structure are obtained using the two-dimensional structure. The optical device which has can be produced.

  The optical device according to the present invention has a simple structure, a high dispersion characteristic capable of realizing a super collimating function, and is useful as a light receiving device having a high dispersion characteristic realized by a photonic crystal having a three-dimensional structure. is there.

  An optical device according to another invention has a simple structure, a high dispersion characteristic capable of obtaining a photonic band gap effect, and a light receiving device having a high dispersion characteristic realized by a photonic crystal having a three-dimensional structure. Useful as such.

1 is a schematic side sectional view of an optical device according to a first embodiment of the present invention. (A) The figure which shows the dispersion characteristic of each i-th material of the two-dimensional array optical element of the optical device of Embodiment 1 of this invention, (b) Two-dimensional array optical element of the optical device of Embodiment 1 of this invention The figure which shows the dispersion surface of each i-th material of this, (c) The figure which shows the dispersion surface when the number m of each i-th material of the two-dimensional arrangement | sequence optical element of the optical device of Embodiment 1 of this invention is enlarged. (A) Schematic diagram showing a ray trajectory when incident light is incident on the optical device according to the first embodiment of the present invention at an incident angle = 0 °. (B) In the optical device according to the first embodiment of the present invention, Schematic diagram showing the ray trajectory when incident light is incident at an incident angle> 0 ° (A) The figure which shows the dispersion characteristic of the two-dimensional arrangement | sequence optical element at the time of arranging each i-th material of the optical device of Embodiment 1 of this invention so that a refractive index may become large according to the distance from a central axis, (b) FIG. 4 is a diagram showing a dispersion surface of a two-dimensional array optical element when the i-th materials of the optical device according to the first embodiment of the invention are arranged so as to have the dispersion characteristics shown in FIG. When the number m of each i-th material 4 is increased in an arrangement in which the refractive index of each i-th material of the optical device of form 1 increases according to the distance from the central axis, the flat dispersion surface and the negative curvature radius Diagram showing an example of the dispersion surface The figure explaining the dispersion surface in the case of outputting diffused light with the optical device of Embodiment 1 of this invention The figure explaining the dispersion surface in the case of outputting parallel light with the optical device of Embodiment 1 of this invention The figure explaining the dispersion surface in the case of outputting condensed light with the optical device of Embodiment 1 of this invention FIG. 4 is a schematic diagram showing a ray locus when a two-dimensional array optical element having a dispersion surface that approximates a parallel light dispersion surface is used as the two-dimensional array optical element of the optical device according to the first embodiment of the present invention. FIG. 3 is a schematic diagram showing a ray locus when a two-dimensional array optical element having a dispersion surface that approximates a light collection and dispersion surface is used as the two-dimensional array optical element of the optical device according to the first embodiment of the present invention. (A) Cross-sectional configuration diagram of a two-dimensional array optical element having a refractive index change in the rotation direction of the central axis of the optical device according to the first embodiment of the present invention, (b) the light according to the first embodiment of the present invention. The figure which shows the dispersion characteristic of the two-dimensional arrangement optical element which gives the refractive index change also to the rotation direction of the central axis of the device Side cross-sectional schematic diagram of the optical device of Embodiment 2 of this invention (A) The figure which shows the dispersion characteristic of the one-dimensional photonic crystal of the optical device of Embodiment 2 of this invention, (b) The dispersion | distribution in frequency (omega) 1 of the one-dimensional photonic crystal of the optical device of Embodiment 2 of this invention. Figure showing a face

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input side 0.25 pitch GRIN lens 2 Two-dimensional array optical element 3 Output side 0.75 pitch GRIN lens 4 i-th material 5 Center axis 6 Incident light 7 Output light 8 Incident angle (theta) i
9 Material incident position ri
10 Incident azimuth angle βi
DESCRIPTION OF SYMBOLS 11 Diffused light part 12 Parallel light part 13 Condensed light part 14 One-dimensional photonic crystal 15 Photonic band gap 20 Output angle (theta) o
21 Material output position ro
22 Input surface 23 Output surface 24 Input surface 25 Output surface 26 Dispersion surface 27 Parallel light dispersion surface 28 Concentration dispersion surface 29 Diffuse dispersion surface 30 Parallel light dispersion surface 31 Condensation dispersion surface 32 Dispersion characteristics of photonic crystal

Claims (15)

A first light conversion element having an output surface parallel to the input surface, the output position corresponding to the incident direction of light incident from the input surface in a one-to-one relationship;
The optical characteristic at the incident position corresponding to the exit position is uniform in the direction perpendicular to the output face of the first light conversion element, arranged close to the output face, and according to the incident direction. An optical element corresponding to
A second light conversion element that is arranged in the vicinity of the optical element so that the light emitted from the optical element is incident thereon, and that outputs in the emission direction corresponding to the incident position of the light in a one-to-one relationship; Optical device provided in order from the incident side.   The relationship between the incident position and the exit position of light incident on the optical element from a predetermined position is such that the direction of a straight line connecting the incident position and the exit position is parallel to the direction perpendicular to the output surface. The optical device according to claim 1.   3. The refractive index distribution type lens according to claim 2, wherein each of the first light conversion element and the second light conversion element is a refractive index distribution type lens having a refractive index distribution that decreases in a parabolic manner according to a distance from the central axis at a maximum on a central axis. The optical device described.   By setting the refractive index of the optical element to be a refractive index that decreases according to the distance from the central axis, light diffused with respect to input light incident on the first light conversion element in a predetermined incident angle range is provided. The optical device according to claim 3, wherein the optical device outputs from the two-light conversion element.   By setting the refractive index of the optical element to be a refractive index that increases according to the distance from the central axis, parallel light or condensed light with respect to input light incident on the first light conversion element in a predetermined incident angle range. The optical device according to claim 3, wherein the light is output from the second light conversion element.   The optical device according to claim 3, wherein the optical element has a structure in which a plurality of optical objects are arranged in a two-dimensional direction perpendicular to the central axis.   The optical device according to claim 6, wherein the refractive indexes of the optical objects are different. The refractive index of each optical object can be changed by electrical control,
The output from the second light conversion element is controlled by controlling the relationship between the refractive index of each optical object, the distance of each optical object from the central axis, and the rotation angle around the central axis. 8. The optical device according to 7.   The optical device according to claim 7, wherein a relationship between a refractive index of each optical object and a distance from the central axis is varied according to a rotation angle around the central axis.   Regarding the rotation angle around the central axis, the relationship between the refractive index of each optical object and the distance from the central axis has a rotation angle range in which the correlation is negative and a rotation angle range in which the correlation is positive. The optical device according to claim 9. A direction perpendicular to the input surface of the light incident from the input surface, the output surface having an output surface parallel to the input surface corresponding to the incident direction of the light incident from the input surface. A first light conversion element that reduces an exit angle at an exit position on the exit surface with respect to an incident angle with respect to
An optical device comprising: a photonic crystal disposed in the vicinity of the output surface and having a periodic structure in a direction perpendicular to the input surface of the first light conversion element.   The optical device according to claim 11, wherein a period of the periodic structure of the photonic crystal is substantially equal to an integral multiple of a half wavelength of predetermined light incident from the first light conversion element.   It is arranged close to the photonic crystal so that light having a wavelength other than the wavelength of the predetermined light emitted from the photonic crystal is incident, and has a one-to-one correspondence with the incident position of the light. The optical device according to claim 12, comprising a second light conversion element that outputs in the emission direction.   14. The refractive index distribution type lens according to claim 13, wherein the first light conversion element and the second light conversion element are refractive index distribution type lenses having a refractive index distribution that decreases in a parabolic manner according to a distance from the central axis at a maximum on a central axis. The optical device described. The first light conversion element is a gradient index lens having an optical path length of 0.25 + 0.5 × i pitch (i is an integer of 0 or more);
The optical device according to claim 3 or 14, wherein the second light conversion element is a gradient index lens having an optical path length of 0.25 + 0.5 × j pitch (j is an integer of 0 or more).