JP2005316233A - Method and apparatus for forming photonic crystal structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photonic crystal structure forming method and apparatus by which a photonic crystal structure can be formed in a short time using an optical system composed of a small number of optical elements. <P>SOLUTION: This apparatus for forming photonic crystal structure includes a luminous flux radiating means 1 which radiates a plurality of parallel beams having coherence and a semi-polygonal lens 2 to which a plurality of parallel beams are made incident on the bottom face arranged perpendicularly to the parallel beams. Incidentally, the luminous flux radiating means 1 is composed of a laser 11 that radiates one luminous flux, a diffraction plate 12 that splits one luminous flux into a plurality of luminous fluxes, and a collimator lens 13 that makes the plurality of luminous flux parallel to the optical axis of the laser 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photonic crystal structure creation method and apparatus, and in particular, can create a photonic crystal structure in a photoreactive material such as an optical recording medium, a magnetic recording medium, a magneto-optical recording medium, or an optical fiber cladding. The present invention relates to a photonic crystal structure creation method and apparatus.

  In recent years, in the field of information recording, development and practical use of next-generation optical information storage media have been promoted aiming at high density and large capacity.

  Elemental technologies for high density include shortening the wavelength of recording / reproducing light, increasing the numerical aperture of the objective lens of the optical system, increasing the number of recording marks, and three-dimensional multilayer recording.

  In particular, three-dimensional multilayer recording on an optical storage medium can dramatically increase the density and capacity compared to other technologies, but in order to control the recording / reproducing position, an optical It is necessary to create a photonic crystal that is a structure in which units of about the same wavelength are periodically arranged.

  In the field of magnetic recording or magneto-optical recording, a technique for increasing the density of storage by creating a photonic crystal structure in a recording medium has also been proposed.

  Furthermore, in the field of optical communications, practical application of photonic crystal fibers capable of realizing high speed and large capacity is being promoted, but in photonic crystal fibers, a photonic crystal structure may be provided periodically around the center. Necessary.

  As described above, the technology for creating a photonic crystal structure in a photoreactive material is becoming increasingly important in the field of information storage and transmission, and various proposals have already been made for photonic crystal structure creation methods and apparatuses. Has been made.

  For example, a method of creating a photonic crystal structure using multibeam interference exposure has already been proposed (see Patent Document 1).

  FIG. 10 is a perspective view of an apparatus used for creating the photonic crystal structure according to the above proposal. The beam light emitted from the He—Cd laser 91 is converted into three beams by the beam splitter 92 and the beam splitter 93. Separated into light.

  The three light beams are reflected by the reflecting mirrors 94, 95, 96, 97, and 98, guided into the photoreactive material 99 in the glass cell, exposed with interference fringes, and cured to create a micro periodic structure. doing. In this case, the period can be changed by adjusting the collision angle of the beam light.

  Furthermore, a method for easily creating a diamond-structured photonic crystal structure that reflects only light of a specific wavelength has also been proposed (see, for example, Patent Document 2).

  FIG. 11 is a block diagram of the diamond structure photonic crystal structure creation apparatus according to the above proposal, in which the diffractive optical element 101 that separates the laser beam light and each beam light separated by the diffractive optical element 101 is collimated. The first lens 102, the shielding plate 103 having a through-hole through which only necessary light from the collimated light beam is passed, and the light beam that has passed through the shielding plate 103 is focused in the photoreactive material 104. And a second lens 106 for focusing on 105.

As shown in the front view, the shielding plate 103 has through-holes at the center and at the four surroundings.
JP 2000-329920 A ([0007], FIG. 1) Japanese Patent Laying-Open No. 2003-084158 ([0012] to [0015], FIG. 5)

  However, since the conventional photonic crystal structure creation method shown above requires a plurality of optical elements such as a beam splitter, a reflector, a lens, or a shielding plate, the creation apparatus is not only expensive, There is a problem that it takes time to adjust the optical axis between the optical elements.

  In addition, when electron drawing is performed using an electron beam instead of a laser as a radiation source, there is a problem that drawing takes a long time.

  The present invention has been made to solve the conventional problems, and is a photonic crystal structure capable of creating a photonic crystal structure in a short time using an optical system composed of a small number of optical elements. It is an object to provide a creation method and apparatus.

  The photonic crystal structure creation method according to the present invention includes a semi-polyhedral lens installation step of installing a semi-polyhedral lens having a plurality of side surfaces inclined at an angle determined by the period of the photonic crystal with respect to the bottom surface, and the semi-polyhedral lens. The photoreactive material is disposed in the interference fringe generation region, and the photoreactive material is exposed with an interference fringe generated by a plurality of coherent light beams perpendicularly incident on the bottom surface of the half-polyhedral lens. And an exposure stage.

  With this configuration, a photonic crystal structure can be created with a laser beam using an optical system composed of a small number of optical elements.

  The photonic crystal structure creation device according to the present invention includes a light flux radiating means for radiating a plurality of coherent parallel lights, and the plurality of parallel lights arranged perpendicular to the plurality of parallel lights. And a semi-polyhedral lens incident on the bottom surface.

  With this configuration, a photonic crystal structure can be created with a laser beam using an optical system composed of a small number of optical elements.

  The photonic crystal structure creation device according to the present invention has a configuration in which the semi-polyhedral lens is an N pyramid (where N ≧ 3) lens.

  With this configuration, a two-dimensional phonic crystal structure can be created.

  The photonic crystal structure creation device according to the present invention has a configuration in which the semi-polyhedral lens is an N-pyramidal frustum (where N ≧ 3) lens.

  With this configuration, a three-dimensional phonic crystal structure can be created.

  The photonic crystal structure creation device according to the present invention is disposed at a condensing point of the N-pyramidal lens, and is disposed on the opposite side of the N-pyramidal lens with respect to the photoreactive material from which the photonic crystal structure is created. The mirror includes a reflecting mirror that reflects a light beam that passes through the center of the N-pyramidal lens leaking from the photoreactive material toward the photoreactive material.

  With this configuration, a three-dimensional phonic crystal structure can be created more flexibly.

  The present invention includes a light flux radiating means for radiating a plurality of coherent parallel light beams, and a semi-polyhedral lens on which a plurality of parallel light beams are incident on a bottom surface arranged perpendicular to the plurality of parallel light beams. By providing, it becomes possible to create a photonic crystal structure in the photoreactive material using a small number of optical elements.

  Embodiments of a photonic crystal structure creation apparatus according to the present invention will be described below with reference to the drawings.

  FIG. 1 shows a block diagram of a first embodiment of a photonic crystal structure creation apparatus according to the present invention.

  That is, the photonic crystal structure creating apparatus according to the present invention includes a light flux radiating means 1 that emits a plurality of coherent parallel lights, and the plurality of parallel lights perpendicular to the plurality of parallel lights. And a semi-polyhedral lens 2 that is incident on the arranged bottom surface.

  The light beam emitting means 1 includes a laser 11 that emits one light beam, a diffraction plate 12 that separates one light beam into a plurality of light beams, and a plurality of light beams that are parallel to the optical axis of the laser 11. And the collimating lens 13.

FIG. 2 is a side sectional view of a half polyhedron lens 2 applied to the photonic crystal structure creating apparatus according to the present invention. The bottom surface 2a of the half polyhedron lens 2 is the light of the laser 11 as shown in FIG. Arranged perpendicular to the axis. The first side surface 2b ₁ of the semi-polyhedral lens 2 forms an angle α ₁ with respect to the bottom surface 2a, and the second side surface 2b ₂ forms an angle α ₂ with respect to the bottom surface 2a. Further, the semi-polyhedral lens 2 may have third, fourth,... Side surfaces.

  The photoreactive material 3 in which the photonic crystal structure is created is disposed in an interference fringe generation region by the semi-polyhedral lens 2.

  Next, in the photonic crystal structure creation method according to the present invention, the semi-polyhedral lens 2 having a plurality of side surfaces inclined at an angle determined by the period of the photonic crystal with respect to the bottom surface is installed.

  Next, the photoreactive material 3 is disposed in the interference fringe generation region by the semi-polyhedral lens. Finally, the photoreactive material is exposed with a plurality of coherent light beams that are perpendicularly incident on the bottom surface 2a of the half-polyhedral lens 2.

  Hereinafter, the period of the photonic crystal when the quadrangular pyramid lens 21 is used as the semi-polyhedral lens 2 will be described with reference to the path diagram of the luminous flux in FIG.

  In the following description, an axis perpendicular to the bottom surface of the half-polyhedral lens 2 is referred to as a Z-axis, and axes perpendicular to the bottom surface of the half-polyhedral lens 2 are referred to as an X-axis and a Y-axis.

The angle formed by the side surface with respect to the bottom surface of the quadrangular pyramid lens 21 is α, and the refractive indexes of the quadrangular pyramid lens 21, air, and the photoreactive material 3 are n ₁ , n ₀ (= 1.0), and n ₂ , respectively. .

  When a plurality of collimated light beams are irradiated perpendicularly to the bottom surface of the quadrangular pyramid lens 21, the incident angle of the light beams on the quadrangular pyramid lens 21 is α.

  The following Snell's law is established between the incident angle α and the refraction angle β.

  Further, the following equation is established between the incident angle α and the refraction angle β to the quadrangular pyramid lens 21 and the incident angle γ to the photoreactive material 3.

  Further, the Snell's law of the following equation is also established between the incident angle γ and the refraction angle θ of the photoreactive material 3 for the luminous flux.

  From the above three formulas, the following formula is established.

  Assuming that the amount of light absorbed in the photoreactive material 3 is extremely small, the propagation coefficient k of the light beam in the photoreactive material 3 is defined by the following equation.

  The Z-axis component kz along the traveling direction of the light flux having the propagation coefficient k, and the X-axis and Y-axis components kx and ky that are orthogonal to each other in a plane orthogonal to the Z-axis can be expressed by the following equations.

Light beams f ₁ , f ₂ , f ₃ , and f ₄ emitted from the four side surfaces of the quadrangular pyramid lens 21 can be expressed by the following equations. The amplitude is 1.

Note that f ₁ and f ₂ travel in the XZ plane symmetrically with respect to the Y axis, and f ₃ and f ₄ travel in the YZ plane symmetrical with respect to the X axis.

Therefore, the light intensity I _A at an arbitrary point A (x, y, z) in the photoreactive material 3 due to the interference of the _four light beams f ₁ , f ₂ , f ₃ , f ₄ can be expressed by the following equation. it can.

As can be understood from the above equation, the intensity I _A of the interference light of the four light beams do not change in the Z-axis direction, the light intensity when the following equation is established is zero.

Therefore, the interference fringes of the _four light beams f ₁ , f ₂ , f ₃ , and f ₄ emitted from the quadrangular pyramid lens 21 form a cylindrical group as shown in FIG. A photonic crystal structure corresponding to is created.

For example, if n ₁ = n ₂ = 1.5 and α = 30 degrees, sin θ = 0.2125.

  On the X axis where y = 0, the light intensity is maximized at the point where the following equation holds.

  Therefore, the pitch of the highest point of light intensity, that is, the pitch Px in the X-axis direction of the photonic crystal structure is expressed by the following equation.

  Therefore, when the wavelength λ of the light beam is 532 nanometers, the pitch Px in the X-axis direction is 1669 nanometers.

  FIG. 5 is a graph showing the change of the angle α formed by the side surface with respect to the bottom surface of the quadrangular pyramid lens 21 and the pitch Px in the X-axis direction of the photonic crystal body. It can be seen that the pitch of the crystal structure can be changed.

  In FIG. 6, kx = ky = 1.0 and the negative photoreactive material, which is the photoreactive material 3, is exposed to an interference pattern, and a photonic crystal structure is formed in the photoreactive material. I understand.

  As described above, according to the first embodiment, a photonic crystal structure that does not change in the Z-axis direction and has a periodic structure in the XY axis plane is created in the photoreactive material 3. It becomes possible.

  Next, a second embodiment of the photonic crystal structure creation device according to the present invention will be described.

  FIG. 7 shows a block diagram of a second embodiment of the photonic crystal structure creation apparatus according to the present invention. The first embodiment except that the quadrangular pyramid lens 21 becomes the quadrangular pyramid lens 22 in FIG. Since the configuration is the same as that of the embodiment, detailed description is omitted.

  The period of the photonic crystal structure created by the photonic crystal structure creating apparatus according to the second embodiment is as follows.

When the quadrangular frustum lens 22 is used, in addition to the four light beams shown in [Equation 7], the light passes through a plane parallel to the bottom surface of the central portion of the quadrangular frustum lens 22 expressed by the following equation. Interference fringes of five light beams including the light beam f ₅ are generated in the photoreactive material 3.

Therefore, the light intensity I _B at the point B (x, y, z) in the photoreactive material 3 is expressed by the following equation.

  Here, T is defined by the following equation.

Then, the light intensity I _{B at} the point B is expressed by the following equation.

Therefore, I _B = 0 when the following equation holds.

  Here, if T = 0.5, the following equation is established.

  Therefore, the interference pattern has a zero intensity portion at the following pitch in the Z-axis direction.

  As described above, according to the second embodiment, as shown in FIG. 8, a photonic crystal structure having a periodic structure in the Z-axis direction and the XY plane is created in the photoreactive material 3. It becomes possible to do.

  Next, a third embodiment of the photonic crystal structure creation device according to the present invention will be described.

  FIG. 9 shows a block diagram of a third embodiment of the photonic crystal structure creation device according to the present invention. The photoreactive material 3 is radiated from the center of the quadrangular pyramid lens 22 behind the photoreactive material 3 and passes through the photoreactive material 3. Since the configuration is the same as that of the second embodiment except that the reflecting mirror 4 that reflects the luminous flux is installed, detailed description thereof is omitted.

A light beam f ₆ radiated from the central portion of the quadrangular pyramid lens 22 and transmitted through the photoreactive material 3 and reflected by the reflecting mirror 4 is expressed by the following equation.

Therefore, the intensity I _C of the interference pattern by the six light beams from f ₁ to f ₆ at the point C (x, y, z) in the photoreactive material 3 is expressed by the following equation.

  As can be understood from the above equation, the light intensity at point C is equal to the X-axis component, the Y-axis component, and the Z-axis component of the six light beams. Even the period of the photonic crystal structure can be changed flexibly.

  In the second embodiment and the third embodiment, the half-polyhedral lens is a quadrangular pyramid lens and a quadrangular pyramid lens, respectively, but may be an N (≧ 3) pyramid or an N (≧ 3) pyramid. It is clear.

  As described above, the polyhedral lens used in the photonic crystal structure creation device according to the present invention can use glass for ultraviolet rays such as fused silica and calcium fluoride, or glass for general lenses such as crown glass and synthetic quartz. . The polyhedral lens preferably has a high transmittance at the wavelength of the laser beam used. Furthermore, it is also desirable to apply an antireflection coating to suppress reflection at the interface.

  The reflector used in the third embodiment may be a normal aluminum vapor deposition mirror, but it is desirable to use a reflector for laser light with suppressed wavefront aberration and surface roughness.

  As described above, the photonic crystal structure creation method and apparatus according to the present invention has an effect that a photonic crystal structure can be created in a photoreactive material with a simple optical system. It is valid.

1 is a block diagram of a first embodiment of a photonic crystal structure creation device according to the present invention. It is a sectional side view of the semi-polyhedral lens used with the photonic crystal structure creation apparatus which concerns on this invention. 1 is a path diagram of a light beam in a first embodiment of a photonic crystal structure creation device according to the present invention. It is a perspective view of the interference fringe in 1st Embodiment of the photonic crystal structure creation apparatus which concerns on this invention. It is a graph which shows the relationship between the inclination-angle of the side surface of the quadrangular pyramid lens in the 1st Embodiment of the photonic crystal structure creation apparatus which concerns on this invention, and the pitch of an interference fringe. 1 is a structural diagram of a photonic crystal according to a first embodiment of a photonic crystal structure creation device according to the present invention. It is a block diagram of 2nd Embodiment of the photonic crystal structure creation apparatus which concerns on this invention. It is a perspective view of the interference fringe in 2nd Embodiment of the photonic crystal structure creation apparatus which concerns on this invention. It is a block diagram of 3rd Embodiment of the photonic crystal structure creation apparatus which concerns on this invention. It is a block diagram of the conventional photonic crystal structure creation apparatus. It is a side view of the conventional photonic crystal structure creation apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light beam radiation | emission means 11 Laser 12 Diffraction plate 13 Collimating lens 2 Semi polyhedral lens 21 Square pyramid lens 22 Square pyramid lens 3 Photoreactive material 4 Reflective mirror

Claims (5)

A semi-polyhedral lens installation step of installing a semi-polyhedral lens having a plurality of side surfaces inclined at an angle determined by the period of the photonic crystal with respect to the bottom surface;
A photoreactive material arrangement step of arranging a photoreactive material in an interference fringe generation region by the half-polyhedral lens;
An exposure step of exposing the photoreactive material with interference fringes generated by a plurality of coherent light beams incident perpendicularly to the bottom surface of the semi-polyhedral lens. Luminous flux emitting means for emitting a plurality of parallel lights having coherence,
A photonic crystal structure creation apparatus including a semi-polyhedral lens in which the plurality of parallel lights are incident on a bottom surface arranged perpendicular to the plurality of parallel lights. The photonic crystal structure creation apparatus according to claim 2, wherein the half-polyhedral lens is an N pyramid (where N ≧ 3) lens. The photonic crystal structure creation device according to claim 2, wherein the half-polyhedral lens is an N-pyramidal frustum (where N ≧ 3) lens. A reflecting mirror disposed at the condensing point of the N-pyramidal lens and disposed on the opposite side of the N-pyramidal lens with respect to the photoreactive material for creating a photonic crystal structure, and leaks from the photoreactive material The photonic crystal structure creation apparatus according to claim 4, further comprising a reflecting mirror that reflects a light beam transmitted through a central portion of the N-pyramidal frustum lens toward the photoreactive material.

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