JP4264235B2 - Method for forming a three-dimensional photonic crystal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a woodpile type and a jabronovite type three-dimensional photonic crystal having a diamond crystal structure.
[0002]
[Prior art]
As is well known to those skilled in the art, a photonic crystal has been proposed as an element for improving the performance of light emitting elements, optical circuits, and the like. A photonic crystal is a medium exhibiting a structure in which the refractive index varies with the period of the wavelength of light, and is typically a one-dimensional photonic crystal having a simple periodic structure such as a multilayer film, or a hole or column arrangement formed in a substrate. In addition to the two-dimensional photonic crystal, a three-dimensional photonic crystal having a three-dimensional mosaic structure has been proposed.
[0003]
As a method for forming a three-dimensional photonic crystal, a sequential lamination method using a semiconductor micromachining technique and a microsphere method using a large number of microspheres such as silica or polystyrene have been proposed. However, the sequential lamination method and the microsphere method form photonic crystals with sufficient accuracy because the manufacturing cost is remarkably high because it is necessary to perform a remarkably complicated process many times. It is difficult if not impossible to do so.
[0004]
In Japanese Patent Laid-Open No. 2000-329920, the inventors irradiate a photo-curable synthetic resin with two or three laser beams generated by splitting into two or three from a common laser light source. A method of forming a three-dimensional photonic crystal, characterized in that a light interference pattern is generated and a photocurable synthetic resin is cured corresponding to the laser light interference pattern, has been proposed. According to such a method using a laser beam interference pattern, a three-dimensional photonic crystal can be formed considerably simpler and at a lower cost and with a considerably higher accuracy than the sequential lamination method and the microsphere method.
[0005]
[Problems to be solved by the invention]
However, the three-dimensional photonic crystal formed by the method disclosed in the above Japanese Patent Laid-Open No. 2000-329920 proposed by the present inventors has a simple hexagonal lattice structure. As a three-dimensional photonic crystal, a crystal having a diamond crystal structure capable of obtaining an ideal photonic band gap, not a hexagonal lattice structure, is excellent. As a three-dimensional photonic crystal having a diamond crystal structure, Have proposed woodpile type (also called layer-by-layer type) photonic crystals and jabronovite type photonic crystals.
[0006]
The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is that a three-dimensional photonic crystal having a diamond crystal structure, that is, a woodpile type three-dimensional photonic crystal and a jabronovite type three-dimensional photonic crystal. It is to provide a new and useful method which can be formed considerably easily and inexpensively and with extremely high accuracy.
[0007]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have improved the above-mentioned main technique by improving the laser light irradiation mode in the method disclosed in the above-mentioned Japanese Patent Laid-Open No. 2000-329920 previously proposed by the present inventors. We found that we can achieve the objective.
[0008]
That is, according to one aspect of the present invention, as a method for achieving the main technical problem, a photosensitive synthetic resin is irradiated with four laser beams to generate a first laser beam interference pattern, and Irradiating a photosensitive synthetic resin with four laser beams to generate a second laser beam interference pattern substantially perpendicular to the first laser beam interference pattern. A method of forming a woodpile type three-dimensional photonic crystal having a structure is provided.
[0009]
In a preferred embodiment, each of the four laser beams that generate the first laser beam interference pattern and the four laser beams that generate the second laser beam interference pattern are laser beams from a common laser light source. Is a laser beam generated by spectroscopically dividing the light into four, substantially defining a square pyramid, and the first laser beam interference pattern and the second laser beam interference pattern are two-dimensional square lattices of a prismatic array. . The photosensitive synthetic resin is a photocurable synthetic resin, and it is preferable that a cured portion cured by laser light irradiation has a diamond crystal structure. Preferably, the photocurable synthetic resin is an ultraviolet curable synthetic resin, the laser light source is a near infrared pulse laser, and the photosensitive synthetic resin is cured by two-photon absorption. Advantageously, the cured portion of the photosensitive synthetic resin is used as a replica to form the three-dimensional photonic crystal from a material having a high refractive index.
[0010]
According to another aspect of the present invention, a laser beam interference pattern is generated by irradiating three laser beams that are relatively inclined with respect to the central axis of the photosensitive synthetic resin. The photosensitive synthetic resin is rotated 120 degrees around the central axis, and the three laser beams are irradiated again to generate a laser beam interference pattern, and the photosensitive synthetic resin is rotated again 120 degrees, Further, there is provided a method of forming a jabronovite type three-dimensional photonic crystal having a diamond crystal structure, which comprises irradiating the three laser beams to generate a laser beam interference pattern.
[0011]
In a preferred embodiment, the three laser beams are laser beams generated by splitting three laser beams from a common laser light source, substantially defining a regular triangular pyramid, and the laser beam interference pattern is a regular hexagon. It is a two-dimensional triangular lattice of a prismatic array. Preferably, the central axis of the photosensitive synthetic resin and the central axis of the equilateral triangular pyramid defined by the three laser beams form an inclination angle of 35 degrees. The photosensitive synthetic resin is a photo-curable synthetic resin, and it is preferable that the non-cured portion excluding the cured portion cured by laser light irradiation has a diamond crystal structure. Preferably, the photocurable synthetic resin is an ultraviolet curable synthetic resin, the laser light source is a near infrared pulse laser, and the photosensitive synthetic resin is cured by two-photon absorption. Advantageously, the cured portion of the photosensitive synthetic resin is used as a replica to form the three-dimensional photonic crystal from a material having a high refractive index.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the method for forming a three-dimensional photonic crystal of the present invention will be described in more detail with reference to the accompanying drawings.
[0013]
Referring to FIG. 1, in a preferred embodiment of the method of the present invention for forming a woodpile photonic crystal, a glass cell 4 which may be a rectangular or cubic shape filled with a photosensitive synthetic resin 2. Prepare. The photosensitive synthetic resin 2 is preferably an uncured photocurable synthetic resin, particularly an ultraviolet curable synthetic resin. As an ultraviolet curable synthetic resin which can be used conveniently, the ultraviolet curable synthetic resin currently marketed as a brand name "SCR500" from Nippon Synthetic Rubber Co., Ltd. can be mentioned, for example.
[0014]
The glass cell 4 is held in a required state by an appropriate holding means (not shown), and the first surface (the lower surface in FIG. 1) S1 of the photosensitive synthetic resin 2 filled in the glass cell 4 is numbered as a whole. Four laser beams LB1, LB2, LB3, and LB4 are irradiated by the laser beam irradiation means indicated by 6. In the illustrated embodiment, the laser light irradiation means 6 includes a common laser light source 8, three splitters 10, 12 and 14 and five reflecting mirrors 16, 18, 20, 22 and 24. The laser light source 8 is preferably a laser light source that emits a near-infrared pulse laser, such as a titanium sapphire (Ti: Sapphire) laser. The pulse laser beam emitted from the laser light source 6 is split into two laser beams by the splitter 10, and one of the split two laser beams is reflected by the reflection mirror 16 and reaches the splitter 12, and the other is the reflection mirror. 18 is reflected to the splitter 14. The laser beam reaching the splitter 12 is further split into two laser beams LB1 and LB2, and the laser beam reaching the splitter 14 is further split into two laser beams LB3 and LB4. The laser beam LB1 is reflected by the reflection mirror 24 and applied to the first surface S1 of the synthetic resin 2. The laser beam LB2 is reflected by the reflection mirror 20 and the reflection mirror 24 and is applied to the first surface S1 of the synthetic resin 2. The laser beam LB3 is reflected by the reflection mirror 24 and applied to the first surface S1 of the synthetic resin 2. The laser beam LB4 is reflected by the reflection mirror 22 and the reflection mirror 24, and is irradiated on the first surface S1 of the synthetic resin 2.
[0015]
The optical path lengths of the laser beams LB1, LB2, LB3, and LB4 from the laser light source 6 to the first surface S1 of the synthetic resin 2 are set to be substantially the same. Further, the four laser beams LB1, LB2, LB3, and LB4 that are reflected by the reflecting mirror 24 and irradiated onto the first surface S1 of the synthetic resin 2 define a regular quadrangular pyramid, and the apex of the regular quadrangular pyramid is the synthetic resin 2. On the first surface S1. When such four laser beams LB1, LB2, LB3, and LB4 are irradiated onto the first surface S1 of the synthetic resin 2, a laser beam interference pattern 26 as shown in FIG. A laser beam interference pattern 26 that is a two-dimensional square lattice is generated. When the synthetic resin 2 is an ultraviolet curable synthetic resin and the laser beam generated by the laser light source 8 is a near infrared pulse laser, the synthetic resin 2 is cured according to the laser beam interference pattern 26 by two-photon absorption. Thus, a number of prism arrays 30 (FIG. 3) are cured. When a large number of prism arrays 30 are cured by two-photon absorption, only the vicinity of the peak value of the pulse laser is contributed to the curing, so that the four sides of the cured prisms can be made into a sufficiently sharp upright plane. The spacing between adjacent prisms in the laser beam interference pattern 26 is defined by the tilt angles α of the four laser beams LB1, LB2, LB3 and LB4 that define a regular quadrangular pyramid, and the spacing decreases as the tilt angle α is increased. It is done.
[0016]
When the irradiation of the above-described four laser beams LB1, LB2, LB3, and LB4 on the first surface S1 of the synthetic resin 2 is completed, as shown by a two-dot chain line in FIG. 1, the glass cell filled with the synthetic resin 2 4 is rotated 90 degrees, and the four laser beams LB1, LB2, LB3, and LB4 are irradiated in the same manner on the second surface S2 that is substantially perpendicular to the first surface S1 of the synthetic resin 2. The Therefore, the laser beam interference pattern 26 that is a two-dimensional square lattice of the prism array 28 is also generated with respect to the second surface S2 of the synthetic resin 2, and thus a large number of prism arrays 32 (FIG. 3) are cured. Regarding the synthetic resin 2, the laser beam interference pattern 26 generated by the four laser beams LB1, LB2, LB3, and LB4 irradiated on the second surface S1 has four laser beams irradiated on the second surface S2. It is substantially perpendicular to the laser beam interference pattern 26 generated by the light beams LB1, LB2, LB3, and LB4. In other words, for a large number of prism arrays 30 that are cured by irradiation of the four laser beams LB1, LB2, LB3, and LB4 on the first surface S1, four laser beams LB1 on the second surface S2, A large number of prism arrays 32 cured by irradiation of LB2, LB3, and LB4 are substantially vertical, and each of the multiple prism arrays 32 extends between adjacent prism arrays 30 in a specific direction (vertical direction in FIG. 3). I'm damned. Therefore, when the synthetic resin 2 in the glass cell 4 is taken out and the uncured portion is removed by washing with, for example, an ethanol solution, a woodpile photonic crystal 34 as shown in FIG. 3 is formed. Such a woodpile type three-dimensional photonic crystal 34 has a diamond crystal structure having an ideal photonic band gap.
[0017]
After irradiating the first surface S1 of the synthetic resin 2 with the four laser beams LB1, LB2, LB3, and LB4, the glass cell 4 is rotated 90 degrees and four laser beams are applied to the second surface S2 of the synthetic resin 2. Instead of irradiating the light beams LB1, LB2, LB3, and LB4, if desired, the entire laser light irradiation means 6 or a part of its constituent elements may be appropriately moved with respect to the glass cell 4 so that the synthetic resin 2 The second surface S2 can be irradiated with four laser beams LB1, LB2, LB3, and LB4.
[0018]
The structure shown in FIG. 3 formed from a cured synthetic resin can be used as it is as a woodpile type three-dimensional photonic crystal, but the photonic crystal is formed from a material having a high refractive index. It is desirable. Therefore, the structure shown in FIG. 3 formed from a cured synthetic resin is used as a so-called replica, and is made from a material having a high refractive index, for example, titanium oxide (TiO ₂ ) or silicon oxide (SiO ₂ ). It is preferable to form a woodpile type three-dimensional photonic crystal having a structure as shown in FIG.
[0019]
FIG. 4 illustrates a preferred embodiment of the method of the present invention for forming a yavnobyte type three-dimensional photonic crystal. In the illustrated embodiment, an inclined support plate 38 is fixed to the tip of an inclined shaft 36 that is rotatably mounted. A glass cell 42 filled with a photosensitive synthetic resin 40, preferably a photosensitive synthetic resin 40, preferably an ultraviolet curable synthetic resin, is mounted on the inclined support plate 38 by an appropriate means such as vacuum adsorption. The The tilt angle θ of the tilt shaft 36 with respect to the vertical is preferably 35 degrees. The photosensitive synthetic resin 40 filled in the glass cell 42 is irradiated with three laser beams LB1, LB2 and LB3 by a laser beam irradiation means indicated as a whole by numeral 44. The laser light irradiation means 44 includes a laser light source 46, two splitters 48 and 50, and five reflection mirrors 52, 54, 56, 58 and 60. The laser light source 46 is advantageously in the form of emitting a near infrared pulsed laser such as a titanium sapphire laser. The pulse laser beam emitted from the laser light source 46 is split into two laser beams by the splitter 48. One of the two split laser beams LB1 is reflected by the reflecting mirrors 52 and 60 and irradiated onto a predetermined plane (ie, upper surface) S1 of the synthetic resin 40. The other of the two laser beams dispersed by the splitter 48 is guided to the splitter 50 and further split into two laser beams by the splitter 50. One LB2 of the two laser beams dispersed by the splitter 50 is reflected by the reflection mirrors 54, 56 and 60 and is irradiated onto the plane 40 of the synthetic resin 40. The other LB3 of the two laser beams dispersed by the splitter 50 is reflected by the reflection mirrors 58 and 60 and is irradiated onto the plane S1 of the synthetic resin 40.
[0020]
The optical path lengths of the laser beams LB1, LB2, and LB3 from the laser light source 46 to the plane S1 of the synthetic resin 40 are set to be substantially the same. Further, the laser beams LB1, LB2, and LB3 reflected by the reflecting mirror 60 and irradiated onto the plane S1 of the synthetic resin 40 define a regular triangular pyramid, and the apex of the regular triangular pyramid is positioned on the plane S1 of the synthetic resin 40. ing. The equilateral triangular pyramids defined by the three laser beams LB1, LB2, and LB3 are substantially vertical, and therefore, the central axis (the central axis of the tilting axis 36) that is substantially perpendicular to the plane S1 of the synthetic resin 40 and three The laser beams LB1, LB2, and LB3 define an angle of inclination of 35 degrees with the central axis of the regular triangular pyramid. When these three laser beams LB1, LB2, and LB3 are irradiated onto the plane S1 of the synthetic resin 40, the laser beam interference pattern 62 as shown in FIG. A laser beam interference pattern 62 that is a grating is generated. When the synthetic resin 40 is an ultraviolet curable synthetic resin and the laser light generated by the laser light source 46 is a near infrared pulse laser, the synthetic resin 40 is cured according to the laser light interference pattern by two-photon absorption. .
[0021]
In the method of the present invention for forming a yavnorobit type three-dimensional photonic crystal, after irradiating the plane S1 of the synthetic resin 40 with three laser beams LB1, LB2 and LB3, the inclined shaft 36 is rotated by 120 degrees, and therefore the synthetic resin is used. The glass cell 42 filled with 40 is rotated 120 degrees, and thereafter, the three laser beams LB1, LB2, and LB3 are again irradiated onto the plane S1 of the synthetic resin 40. Further, after rotating the tilt shaft 36 by 120 degrees, the three laser beams LB1, LB2, and LB3 are irradiated onto the plane S1 of the synthetic resin 40. By doing so, the synthetic resin 40 is cured in a form corresponding to the perforations in the yavnorobit type three-dimensional crystal. In other words, the uncured portion of the synthetic resin 40 has a yavnobyte type photonic crystal structure having a diamond crystal structure. Accordingly, when the synthetic resin 40 in the glass cell 42 is taken out and the uncured portion is washed away with a cleaning liquid such as ethanol, a structure having a form corresponding to the perforation in the yavnobyte type three-dimensional crystal is formed. When such a structure is used as a core-type replica and a structure having a hole corresponding to the structure is formed of a material having a high refractive index such as titanium oxide or silicon oxide, it is illustrated in FIG. As a result, a Yabunorobit type three-dimensional photonic crystal 66 is obtained.
[0022]
【The invention's effect】
According to the present invention, a three-dimensional photonic crystal having a diamond crystal structure, that is, a woodpile-type three-dimensional photonic crystal and a jabronovite-type three-dimensional photonic crystal, can be formed considerably easily and inexpensively and with extremely high accuracy. be able to.
[Brief description of the drawings]
FIG. 1 is a simplified diagram showing a laser beam irradiation mode for forming a woodpile type three-dimensional photonic crystal.
2 is a diagram showing a laser beam interference pattern generated by laser beam irradiation in FIG. 1. FIG.
FIG. 3 is a simplified oblique view showing a formed woodpile type three-dimensional photonic crystal.
FIG. 4 is a simplified diagram showing a laser beam irradiation mode for forming a jabronovite type three-dimensional photonic crystal.
5 is a diagram showing a laser beam interference pattern generated by laser beam irradiation in FIG. 4. FIG.
FIG. 6 is a simplified oblique view showing a formed jabronovite type three-dimensional photonic crystal.
[Explanation of symbols]
2: Photosensitive synthetic resin 6: Laser light irradiation means 26: Laser light interference pattern 34: Woodpile type three-dimensional photonic crystal 40: Photosensitive synthetic resin 44: Laser light irradiation means 62: Laser light interference pattern 66: Jablonovite type 3D photonic crystal

Claims (11)

Irradiating the photosensitive synthetic resin with four laser beams to generate a first laser beam interference pattern, and irradiating the photosensitive synthetic resin with four laser beams to the first laser beam interference pattern Generating a second laser light interference pattern substantially perpendicular to the method, and forming a woodpile type three-dimensional photonic crystal having a diamond crystal structure. Each of the four laser beams that generate the first laser beam interference pattern and the four laser beams that generate the second laser beam interference pattern split the laser beam from the common laser light source into four. 2. The laser light generated by the method, substantially defining a square pyramid, wherein the first laser light interference pattern and the second laser light interference pattern are two-dimensional square lattices of a prismatic array. Method. The method according to claim 1, wherein the photosensitive synthetic resin is a photocurable synthetic resin, and a cured portion cured by laser light irradiation has a diamond crystal structure. 4. The method of claim 3, wherein the photocurable synthetic resin is an ultraviolet curable synthetic resin, the laser light source is a near infrared pulsed laser, and the photosensitive synthetic resin is cured by two-photon absorption. The method according to claim 3 or 4, wherein the three-dimensional photonic crystal is formed from a material having a high refractive index by using the cured portion of the photosensitive synthetic resin as a replica. A laser beam interference pattern is generated by irradiating three laser beams that are relatively inclined with respect to the central axis of the photosensitive synthetic resin, and the photosensitive synthetic resin is centered on the central axis. Rotate 120 degrees, irradiate the three laser beams again to generate a laser beam interference pattern, rotate the photosensitive synthetic resin 120 degrees again, and irradiate the three laser beams again. Generating a laser beam interference pattern, and forming a jabronovite-type three-dimensional photonic crystal having a diamond crystal structure. The three laser beams are laser beams generated by splitting the lasers from the common laser light source into three beams, which substantially define a regular triangular pyramid, and the laser beam interference pattern is a two-dimensional triangular array of regular hexagonal prism arrays. The method of claim 6, wherein the method is a lattice. The method according to claim 6 or 7, wherein the central axis of the photosensitive synthetic resin and the central axis of the equilateral triangular pyramid defined by the three laser beams form an inclination angle of 35 degrees. The method according to any one of claims 6 to 8, wherein the photosensitive synthetic resin is a photocurable synthetic resin, and a non-cured portion excluding a cured portion cured by laser light irradiation has a diamond crystal structure. 10. The method of claim 9, wherein the photocurable synthetic resin is an ultraviolet curable synthetic resin, the laser light source is a near infrared pulsed laser, and the photosensitive synthetic resin is cured by two-photon absorption. The method according to claim 9 or 10, wherein the three-dimensional photonic crystal is formed from a material having a high refractive index by using the cured portion of the photosensitive synthetic resin as a replica.

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