JP2000329920A - Formation of photonic crystal structure by laser interference - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a lattice structure of a photonic crystal by irradiating a photosensitive resin layer with laser beams at a specified angle from one another produced by dividing one laser beam into a plurality of beams to form an image corresponding to the lattice structure which constitutes the photonic crystal structure by the interference of the laser beam. SOLUTION: The laser beam (442 nm) from a He-Cd laser beam source is divided into three beams by beam splitters BS1, BS2 and guided by mirrors M1 to M5 so that the three beams cross in a photosetting resin in a glass cell to interfere, to form interference fringes in the photosetting resin. The period of the obtd. lattice is determined by controlling the crossing colliding angles of the three beams to form the interference fringes. After the photosetting resin is irradiated with three beams having 1 mW intensity and 1.5 mm beam diameter for 30 sec and hardened corresponding to the interference pattern, the liquid resin around the pattern is removed with ethanol and dried. The material used to remove the liquid resin is properly prepared according to the relation with the photosetting resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a two-dimensional periodic lattice structure and a three-dimensional periodic lattice structure having a period of about 1 .mu.m or less by utilizing image formability due to interference of laser light, and in particular, The present invention relates to a method for forming a close-packed lattice structure of a photonic crystal.

[0002]

2. Description of the Related Art A photonic crystal is a material having a three-dimensional refractive index lattice distribution (three-dimensional periodic lattice structure) with a period on the order of the wavelength of light. Just as atomic nuclei are periodically arranged in a solid crystal, a potential is periodically formed three-dimensionally, and photonics are formed based on the same principle as that of a band gap in the energy of electrons that can exist in the crystal. Crystals have a gap in the energy of light that can propagate through them. Light having a wavelength corresponding to the photonic band gap cannot propagate through the structure. Utilizing such properties, it is a new device that is expected to be applied to lasers with extremely high energy efficiency, optical waveguides without propagation loss, optical filters, and the like. However, since a very high-precision three-dimensional micro (nano) shaping technology is required to form a three-dimensional periodic structure at a lattice interval on the order of light wavelength, it has not yet been realized.

[0003] Techniques for forming a three-dimensional photonic crystal structure have been reported by several research groups. To introduce some typical ones, we apply a high-precision etching process for semiconductors and create and stack a number of layers in the z-direction on a two-dimensional periodic structure obtained by chemical etching. A method of obtaining a structure (J. Joannopoulos. P. Villeneuv
e, and S. Fan, "Photonic crystals: putting a new tw
ist on light, "Nature 386, 143 (1997), JGFlemi
ng and S. Y. Lin, "Three-dimensional photonic cryst
al with a stopband from1.35 to 1.95μm, "Opt.Let
t. 24, 49 (1999), etc. ) Or by precipitating and subsequently drying the silica microspheres dispersed in water,
Example in which silica spheres are finely arranged three-dimensionally (I. Tarha
n, M. Zhkin, and G. Watson, "Interferometric techn
ique for the measurement of Photonic band structur
e incol1oidal crystals, "Opt. Lett. 20, 14, 1571 (1
995), etc. ), An example in which a bundle of glass fibers is stretched and thinned to form a two-dimensional periodic structure with a glass rod array (A. Rosenberg, RJ Tonucci, H-B. Lin an)
d AJ. Gampilo, "Near-infrared two-dimensional ph
otonic band-gap materials, "Opt. Lett. 21, 11, 830
(1996), 29, 35, etc.). In the current situation, two types of the above-described lamination method and a method using fine particles (artificial opal) are mainly used for creating a three-dimensional photonic crystal structure. The difficulty in realizing a photonic crystal structure is due to the lack of a modeling technique that can form a three-dimensional periodic distribution of the refractive index with extremely high precision.
In the former method, it is necessary to repeat the deposition (deposition process) and the etching process of a plurality of materials only in the process of processing the structure of one layer, and the manufacturing process is very complicated. In addition, it is necessary to establish a technology that can precisely form the periodic structure of each layer on the order of nanometers. Further, in order to obtain a three-dimensional periodic structure, a process of laminating them in the z direction is necessary, and there is a limit to the number of layers to be laminated at this stage. In the example reported at present, the number of layers in the z direction is 4 to 5 layers, at most about 20 layers (about 1 to 3 in the unit cell of the crystal structure), and it is still difficult to say that it is a three-dimensional crystal. It is the current situation. Also, when the number of layers increases, it is difficult to accurately align the relative positions of the respective layers. In the latter method, the size of the silica microspheres needs to be uniform on the order of nanometers, but in practice there is variation.

[0004]

By the way, when a laser beam is incident on a non-linear medium, the refractive index of the medium changes in proportion to the light intensity, whereby the original light intensity distribution is modulated (at the center of the beam). A strong feedback phenomenon occurs between the light and the medium, which causes the laser beam to be different from the original beam pattern. A non-linear phenomenon that the light propagates through the medium with the profile may occur. Examples include self-focusing, self-trapping, self-fanning, and spatial solitons found in car media and photorefractive media. These are all caused by a change in the refractive index of the medium corresponding to the light intensity distribution. These phenomena are not only interested in autonomous nonlinear phenomena and chaotic phenomena, but also in recent years, such as beam switching, phase conjugate wave and second harmonic generation, and applications in optical computing and laser engineering. This is a phenomenon that is attracting attention. However, in the conventional nonlinear medium, the autonomous nonlinear phenomenon appears only during the irradiation of the laser light, and returns to the original state when the irradiation of the laser light is stopped. In other words, the autonomous nonlinear phenomenon occurs. It could not be memorized.

By injecting a convergent laser beam into a photocurable resin, the present inventors autonomously form a monochromatic beam profile that is not seen in the media reported so far. It has been found that self-formation phenomena of various microstructures are caused (S. Sh.
oji and S.M. Kawata, Proc. CLEO'98, p187
(1998)). Further, it has a characteristic that a structure due to a self-forming phenomenon of a microstructure is recorded. Furthermore, they discovered many non-linear phenomena such as phenomena caused by collision of a plurality of microstructures that are self-forming independently, and discovered that new structures can be developed by using these phenomena (59th Applied Physics) Academic Lecture Meeting ('9
Proceedings of the 8th Japan Society of Applied Physics (59th, 1998. 9, held at Hiroshima University), p857.16p-Q-
7: Collision / merging of self-forming fibers in photocurable resin). The technique uses a laser as convergent light. On the other hand, without converging the laser, if a plurality of light fluxes split by the beam splitter intersect in the photocurable resin at an angle, the regularity due to the interference of the laser light selected by the angle. Since interference fringes are formed and the photocurable resin is cured corresponding to the regular interference fringes, it has been found that removing the uncured portion forms a regular structure of the cured resin. Then, while experimenting by changing the number of light fluxes and the incident angle used for the formation of the interference image, it was discovered that a three-dimensional periodic structure of a wavelength order of near-infrared light to visible light can be formed with high accuracy, and this was further photo-processed. It was considered to utilize it to form a lattice structure of a nickel crystal. Accordingly, an object of the present invention is to provide a method for forming a lattice structure of a photonic crystal by a laser interference method. That is, a pattern of a two-dimensional or three-dimensional lattice structure is formed in a photosensitive resin (optical storage material), for example, in a photocurable resin by laser interference, and the photocurable resin is cured corresponding to the pattern. Another object of the present invention is to provide a method capable of simultaneously forming a plurality of layer structures of the lattice structure by a single laser beam irradiation by removing an uncured material. According to the method, it is possible to form a plurality of layer structures corresponding to the lattice structure constituting the photonic crystal at the same time by one laser light irradiation. For simplicity, the above-described layer structure forming method is referred to as a one-shot method. In an advanced method, a two-dimensional or three-dimensional lattice structure corresponding to a photonic crystal structure can be formed by one irradiation of laser light. In a most preferred embodiment of the present invention, a method is provided that enables a photonic crystal having a multi-layer structure of several hundred layers in a three-dimensional direction (in the z direction) to be formed with high accuracy (fine) in one shot. . At that time, a periodic structure can be formed without requiring scanning.

[0006]

The gist of the present invention is that a photonic crystal structure is formed by irradiating a light beam obtained by dividing a single laser beam into a plurality of photosensitive resin layers at an angle to each other and by interfering with a laser beam. A method of forming a lattice structure of a photonic crystal by interference of laser light using a photosensitive resin, including a step of forming an image corresponding to the lattice structure to be formed in the photosensitive resin layer, A method of forming a lattice structure of a photonic crystal by the laser interference, wherein the material constituting the conductive resin layer is a photocurable resin, and more preferably, forming the photonic crystal by the interference of laser light. The step of forming an image corresponding to the lattice structure to be formed in the photosensitive resin layer corresponds to the two-dimensional lattice structure due to interference of three light beams obtained by dividing one laser beam from one light source. It is to synthesize an image, a single city of image corresponding to a one-dimensional periodic structure according to the interference of the two light beams obtained by dividing the laser beam from the other light source, or,
3 divided one laser beam by one laser light source
An image formed by sequentially performing the formation of an image corresponding to a two-dimensional close-packed structure by interference of light beams and the formation of an image corresponding to a one-dimensional periodic structure by interference of two light beams obtained by dividing one laser beam. Or a method in which a fine photonic crystal structure is created by the laser interference, which is based on interference of four light beams obtained by dividing one laser beam. The present inventor has proposed a method of forming a two-dimensional lattice structure by the interference of three light beams in a photosensitive resin, particularly a photocurable (photopolymerizable) resin, by utilizing the shaping property by the interference of a laser beam. The above-described problem is caused by a method of fusing a method of obtaining a one-dimensional periodic structure by interference of light beams or a method of forming an image of a close-packed lattice structure corresponding to a three-dimensional photonic crystal in the photosensitive resin layer by interference of four light beams. Was solved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings. Creation of close-packed lattice structure corresponding to three-dimensional photonic crystal Realization of a system for producing a three-dimensional periodic lattice structure by fusing the formation of an image corresponding to a two-dimensional lattice structure by the interference of three light beams and the formation of an image corresponding to a one-dimensional periodic structure by the interference of two light beams. First, a three-dimensional periodic lattice structure is manufactured using the system. FIG. 1A [I] shows an optical system of a system for that purpose. First, the laser beam (442 nm) from the He-Cd laser light source is split into three beams by the beam splitters BS1 and BS2, and the mirror M1,
By M2, M3, M4 and M5, the three light beams (in the present specification, the expression “light beam” basically indicates a laser beam obtained by dividing one laser into a plurality of laser beams) in a glass cell. An interference fringe is formed in the photocurable resin by causing them to cross and interfere with each other in the photocurable resin. Make the interference fringes 3
By adjusting the collision angle of the two light beams, the period of the obtained grating is set. After irradiating the photocurable resin with three light beams having a light intensity of 1 mW and a beam diameter of 1.5 mm for 30 seconds to cure the resin in accordance with the interference pattern, the surrounding liquid resin was washed away with ethanol and dried. The material used for removing the liquid resin can be appropriately prepared in relation to the photocurable resin. A grating structure in which rods (column structures extending in the direction perpendicular to the plane (z direction in the xy plane)) in a two-dimensional direction are periodically arranged by an interference pattern of three light beams (this is referred to as "2
Dimensional lattice structure. " ) Is formed. Then, as shown in FIG. 1 (a) [II], two light beams enter from the side of the image corresponding to the two-dimensional lattice structure (the side of the glass cell) and interfere with each other, thereby causing one light in the z direction of the two-dimensional lattice structure. An image corresponding to the two-dimensional periodic structure is formed. Thus, an image corresponding to the lattice structure constituting the three-dimensional photonic crystal is formed in the photosensitive resin (sequential method). Thereafter, the liquid resin (uncured photocurable resin) is washed away with ethanol to obtain a close-packed lattice structure of fine photonic crystals. Further, an image corresponding to a one-dimensional periodic structure in the z direction with respect to an image corresponding to the two-dimensional lattice structure by the interference pattern of the three light beams and an image corresponding to the two-dimensional lattice structure due to the incidence of the two light beams and interference. An image corresponding to a lattice structure constituting a three-dimensional photonic crystal can be formed in the photosensitive resin by simultaneously forming and synthesizing the photosensitive resin using separate laser light sources (simultaneous method). . FIG. 1B shows a top view and a side view of a close-packed lattice structure of the formed three-dimensional photonic crystal. A periodic structure in which rods are arranged in a two-dimensional hexagonal close-packed manner (two-dimensional lattice structure), and a structure in which layers are periodically arranged vertically in the longitudinal direction (one-dimensional periodic structure in the z direction).

B. FIG. 2 shows a method of forming an image corresponding to a lattice structure constituting a three-dimensional photonic crystal structure in a photosensitive resin layer by interference of a light beam obtained by dividing one laser into four. As a method of forming an image corresponding to a lattice structure constituting a three-dimensional photonic crystal structure by exposing a single interference pattern, a method of simultaneously causing four light beams to interfere as shown in FIG. 2A was considered. Using this method, a three-dimensional hexagonal close-packed lattice structure can be obtained by one exposure. However, in this method, the interference pattern formed in the resin becomes a three-dimensional array of points, and the resin cured by the pattern may form a pattern that is not continuous with each other (see FIG. b)), by adjusting the intensity of the incident laser light so that the diameter of the cured resin formed at each point of the interference pattern is slightly larger than the lattice spacing of the interference pattern, The adjacent cured resin particles are connected at the surface as in the case of (1) and the position is fixed, and a precise three-dimensional hexagonal close-packed lattice structure can be obtained.

[0009] Here, a basic technique of obtaining a one-dimensional periodic structure by interference of two light beams and its application to the production of a multidimensional photonic crystal structure, and a two-dimensional lattice structure by interference of three light beams. The method for obtaining the above will be specifically described. C. A shaping method of a photonic crystal structure (in this specification, a two-dimensional lattice structure is also included in the photonic crystal structure in a broad sense) due to interference of two light beams, and a multidimensional photonic crystal structure. 1. First, a system for forming a grating structure having a periodic refractive index in a one-dimensional direction will be described. The optical system of the modeling system is shown in FIG. The laser light from the He-Cd laser was split into two light beams by the beam splitter BS, and the two light beams were caused to interfere in the photocurable resin in the glass cell by mirrors M1, M2, and M3. By adjusting the collision angle of the two light beams that form the interference fringes, the period of the obtained grating can be selected. 2m light intensity on photo-curable resin
After irradiating with W, two light beams having a beam diameter of 1.5 mm for 25 seconds and curing by an interference pattern, the surrounding liquid resin was washed away with ethanol and dried. FIG. 4 is an electron micrograph of the one-dimensional periodic structure produced by the above system. Electron microscopy was performed by evaporating gold with a thickness of 20 nm on the surface of the prepared lattice structure. The pitch of the grating is about 1.2 μm, the depth of the grating is 100 μm, and the size of the entire structure is about 500 × 500 × 100 μm. (B)
Is an enlargement of (a). The number of periods can be changed by changing the laser beam diameter.

[0010] 2. Formation of two-dimensional periodic structure (two-dimensional lattice structure) After irradiating the resin once with laser light, rotate the glass cell of FIG. 3 by 90 ° in the horizontal plane, and irradiate laser light again from the same incident surface to cause interference. By curing in a pattern, a two-dimensional periodic structure can be formed. FIG.
Is an electron micrograph of the periodic structure (two-dimensional lattice structure). 1. Similarly to the above, the resin was formed with a periodic structure in a two-dimensional direction at a pitch of 1.2 μm. Also, 2
By changing the collision angle between two light beams and changing the interval between the formed interference fringes, the obtained grating interval can be changed. FIG. 6 is an electron micrograph of a two-dimensional lattice structure with a lattice spacing of 9.5 μm, produced by changing the collision angle of two light beams. As described above, it has been shown that a one-dimensional lattice structure and a two-dimensional lattice structure can be actually formed by using an interference pattern of two light beams to form a multidimensional lattice structure.

The technique for forming a photonic crystal structure by a laser interference pattern has the following features. Since all layers of the three-dimensional periodic structure can be simultaneously produced by a single laser beam irradiation, and the need for mechanical sample scanning and other processes is eliminated, the modeling accuracy is high. Since the lattice constant of the formed periodic structure is determined by the spacing of the interference fringes of the laser light formed in the resin, it is theoretically possible to produce even a delicate periodic structure with a half-wavelength spacing of the incident laser light. can do. Since the number of layers of the periodic structure to be formed is determined by the number of layers of interference fringes of laser light formed in the resin, the number of layers of the periodic structure that can be produced by increasing the beam diameter of the incident light is limited. Absent. (The laser beam diameter can be changed up to about 50 mm.) Various materials, such as a luminescent or light-amplifying substance,
Alternatively, an electro-optic material, a transparent body, a conductive substance, or the like can be easily doped into the lattice structure.

This method using the interference pattern of the two light beams has the following problems. Several interference pattern exposures are required to form a multi-dimensional grating structure. Considering the application of this method to the formation of a three-dimensional lattice structure, the lattice structure can be extended in three dimensions in the same way, but closed boxes periodically arranged are three-dimensionally stacked. As a result, the liquid photosensitive resin remaining in the gaps between the lattices is trapped by the walls of the cured resin and cannot be washed away. In forming the photonic band gap, the amount of change in the refractive index of the periodic structure needs to be large, and this prevents the liquid resin from remaining in the lattice. As a method to improve these problems, three beams split by one laser at the same time interfere with each other in the resin,
We have developed a method to form a two-dimensional lattice structure at one time by one interference pattern exposure.

D. Here, one laser is divided 3
A method of causing a light beam to interfere in a photosensitive resin to form a two-dimensional lattice structure at a time, that is, a structure in which a large number of rods are arranged with regularity will be described. FIG. 7 shows a modeling method of a two-dimensional close-packed lattice structure using interference of three light beams, and FIG. 7 shows an optical system of a prototype molding system of a two-dimensional lattice structure using interference of three light beams. The laser beam from the He-Cd laser is split into three light beams by using two beam splitters BS1 and BS2, and the light beams are dispersed into the photocurable resin on the sample stage by mirrors M1, M2, M3, M4, and M5. Two light beams were incident from below at an angle to form an interference pattern (stripe or image) in the photocurable resin. C. By adjusting the collision angle of the three light beams forming the interference fringes, the period of the obtained grating and the grating structure can be selected in the same manner as in the method described in (1). After irradiating the photocurable resin with three light beams having a light intensity of 1 mW and a beam diameter of 1.5 mm for 30 seconds to cure the photocurable resin in accordance with the interference pattern, the surrounding uncured liquid state is formed with ethanol. The photocurable resin was washed away and dried. FIG. 8 is an electron micrograph of the two-dimensional lattice structure produced by the above method. Lattice spacing is 1μ
m, the depth (height of the rod) is about 100 μm, and the size of the entire structure is about 500 × 500 × 100 μm as in the above method. In the figure, the portion that looks white is the portion of the cured resin.
It can be seen that a lattice structure in which the following b-shaped structures are closely arranged is shown.

[0014] Features of the shaping method of the two-dimensional lattice structure by interference of three light beams This method solves any problems mentioned in the method using the interference pattern of the two light beams. A two-dimensional lattice structure can be manufactured at once by one exposure of the interference pattern. It is possible to produce not only a tetragonal structure but also a hexagonal close-packed lattice structure. Considering application to the production of a three-dimensional lattice structure,
By forming a layer structure by interference of two light beams in the z direction of the lattice structure obtained by this method, a three-dimensional lattice structure can be obtained, and the liquid resin inside the structure can be washed away with a solvent. is there. Although the close-packed lattice structure shown in FIG. 8 could be produced, the crystal structure was similar to that of the three-dimensional photonic crystal structure using solid crystals, and also from the reports of other research groups. This is a more desirable crystal structure than a tetragonal structure in forming a nickel band gap. The above is described in the above A. And B. The basic principle of manufacturing the three-dimensional photonic crystal structure described in the above section has been described.

The photocurable resin used in the present invention is a urethane acrylate-based ultraviolet curable resin (SCR-500; Nippon Synthetic Rubber) and comprises a photopolymerization initiator, a urethane acrylate monomer and a urethane acrylate oligomer.
FIG. 9 shows an absorption spectrum of the photocurable resin. It absorbs ultraviolet to blue light. When a laser beam having an absorption wavelength is incident on this resin, the photopolymerization initiator in the resin changes into radicals. The radicals cause a polymerization reaction with monomer and oligomer molecules continuously, whereby the resin is cured. The physical properties of the resin are shown below. Physical Properties Table of Photo-Curable Resin Urethane acrylate resin (SCR500: Specific composition will be described later) Refractive index (before curing) 1.53 (wavelength: 441.6 nm) Refractive index (after curing) 1.55 (wavelength: 441.6 nm) Viscosity 850 cps Density 1.11 g / cm ³

In the production of the photonic crystal of the present invention, it is possible to use a known photocurable resin, particularly an ultraviolet curable resin. It is also preferred. The characteristics of the light beam used can be adjusted by selecting a photocurable resin component, for example, a monomer, a prepolymer, a polymer, a photopolymerization initiator and the like. Further, light sensitivity and wavelength sensitivity can be adjusted by adding a sensitizer or the like. The monomer or prepolymer, which is one of the components constituting the photocurable resin used in the present invention, basically contains at least one or more functional groups. It is preferable to add a substance that generates ions or radicals by irradiating a curing energy ray in addition to the main component, a so-called photopolymerization initiator.
The term "functional group" as used herein means an atomic group or a bonding mode that causes reactivity such as a vinyl group, a carboxyl group, and a hydroxyl group. However, the present invention hardens the resin composition by irradiating a curing energy ray. Therefore, a monofunctional or polyfunctional compound having a vinyl group such as an acryloyl group is preferable. Such a monomer having an acryloyl group can be appropriately selected from known ones, and is not particularly limited. However, typical examples thereof include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxyethyl acrylate.
Monofunctional ones such as hydroxypropyl acrylate, acrylate of tetrahydrofuryl and derivatives thereof, dicyclopentenyl acrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate Diethylene glycol diacrylate, polyethylene glycol diacrylate, hydroxypivalic acid ester neopentyl glycol and its derivatives diacrylate, tripropylene glycol diacrylate, dimethylol tricyclodecane diacrylate and other bifunctional ones, trimethylolpropane triacrylate, There are three or more functional groups such as pentaerythritol triacrylate and dipentaerythrol hexaacrylate. In the present invention, it is preferable to use a prepolymer in combination with the above monomer in addition to the above monomer. The prepolymer used in the present invention is not particularly limited as well as the monomer, but may be represented by polyester acrylate, epoxy acrylate, urethane acrylate, etc., and is trifunctional for reasons of low volume shrinkage and flexibility. Hereinafter, a bifunctional or trifunctional one is preferably used. Among these, a mixture of a urethane (meth) acrylate oligomer and a photocurable monomer, and a mixture of a (meth) acrylate oligomer of an epoxy group-containing compound and a photocurable monomer are more preferable.

The laser light used in the present invention includes visible light, ultraviolet light, and the like, and ultraviolet light is preferable for producing a three-dimensional photonic crystal having a fine period. When the light source used is ultraviolet light, it is necessary to add a substance that generates ions or radicals by irradiating ultraviolet light, that is, a photopolymerization initiator, in addition to the above monomers and prepolymers. The photopolymerization initiator used in the present invention is not particularly limited, but typical examples include acetophenone, benzophenone, Michler's ketone, benzyl, benzoin, benzoin ether, benzyldimethyl ketal, and benzoin. Benzoate, α-
Carbonyl compounds such as acyloxime esters; sulfur compounds such as tetramethylthiuram monosulfide and thioxanthone; and phosphorus compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide. These may be used alone or in combination of two or more. Used as
In the present invention, the addition amount of the photopolymerization initiator is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, based on 100 parts by weight of the monomer and / or prepolymer component. If the photopolymerization initiator is less than the above range, the curability will be low. As a preferable mixture, a photosensitive resin composition obtained by adding a photopolymerization initiator to a mixture of a urethane (meth) acrylate oligomer and a photocurable monomer, for example, 2,4-tolylenediisocyanate, hydroxyethyl Acrylate, number average molecular weight 1230 obtained from polyoxytetramethylene glycol having a molecular weight of 650
A resin component comprising a urethane acrylate oligomer having a number average molecular weight of 406 obtained from 2,4-tolylene diisocyanate and hydroxyethyl acrylate, and n
A diluent monomer component consisting of vinylcaprolactam and tricyclodecanediyldimethyleneacrylate;
A photocurable resin composition composed of benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, a photopolymerization initiator composed of 1-hydroxycyclohexylphenyl ketone [trade name "SCR500"
(Manufactured by Nippon Synthetic Rubber Co., Ltd.)]; a resin component composed of a urethane acrylate oligomer obtained from isophorone diisocyanate, hydroxyethyl acrylate, and adipic acid-neopentyl glycol-based polyester polyol; dimethacryloyl ethyl ether of bisphenol A; A diluent monomer component composed of acrylate and neopentyl glycol dimethacrylate, and a photopolymerization initiator composed of 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, and 2,4,6-trimethylbenzoyldiphenylphosphon oxide And a photocurable resin composition composed of the following.

The photocurable resin preferably used in the present invention may contain a polymer in view of strength and the like, but is not preferable in view of washing out the uncured material after curing. Examples of the polymer mentioned here include known polymers such as a polyester resin, an acrylic resin, a urethane resin, and an epoxy resin. Although the photosensitive resin is a photo-curing type (photo-polymerizing type) (so-called negative type), a photo-decomposable or photo-degradable type (so-called positive type) may be used. In the case of a negative type, a portion exposed to light is removed by a solvent or the like.

In order to form a photonic band gap having a wide spectrum width, it is necessary that the difference in the periodic refractive index of the structure is large. The difference in the refractive index of the three-dimensional structure obtained by the present invention is 1.55 for the resin layer and 1.00 for the air layer.
This is a three-dimensional photonic crystal structure using another solid crystal, such as GaAs (refractive index 3.6) and air, a-Si (refractive index 3.24), and SiO ₂ (refractive index). It cannot be said that it is large enough to obtain a wide photonic band gap as compared with the combination of 1.46). However, in the method of the present invention for producing a photonic crystal structure by interference between a photosensitive resin and a laser beam,
Since a multi-layered structure having several hundred layers in the three-dimensional direction (in the z-direction), which cannot be realized by the conventional method, can be formed with high accuracy, the photonic crystal structure can be formed with high accuracy (the microscope shown in FIG. 8). From the photograph, the accuracy of the multilayer structure and the period can be understood.) In addition, a photonic band gap, which cannot be observed with a conventional photonic crystal, can be observed. As for the refractive index difference, it is possible to select a resin having a larger refractive index and to dope the structure with a light amplification material or the like. This is extremely useful in that the technology can be provided.

Example 1 As the photocurable resin, the above-mentioned urethane acrylate-based ultraviolet curable resin (SCR-500; manufactured by Nippon Synthetic Rubber Co., Ltd.), that is, a urethane acrylate monomer to which a photopolymerization initiator is added, a urethane acrylate An oligomer is placed in a glass cell. A. Using the apparatus and conditions described in the above section, a method of obtaining a two-dimensional close-packed structure by interference of three light beams and a method of obtaining a one-dimensional periodic structure by interference of two light beams are combined to have a light intensity of 1 mmW and a beam diameter of 1.5 mm. Under the conditions described above, a three-dimensional periodic structure was produced. After forming an image corresponding to the three-dimensional periodic structure in the photocurable resin, the uncured photocurable resin was removed using ethanol. The micrograph is shown in FIG. It is understood from the lattice constant, the precision of the period, and the total number of periods that an extremely excellent three-dimensional lattice structure is realized. The transmission spectrum measurement confirmed the photonic band effect of the structure.

Example 2 The three-dimensional photonic crystal structure was manufactured by one exposure by the method of the apparatus described in (1). The photosensitive resin composition used in Example 1 was used. Four laser beams (4 mm) having a light intensity of 1 mW and a beam diameter of 1.5 mm
After irradiating with a light beam) and curing according to an interference pattern, the surrounding liquid resin was washed away with ethanol and dried. The photonic band effect of the structure was confirmed by transmission spectrum measurement.

[0022]

As described above, the method for producing a lattice structure of a three-dimensional photonic crystal using the interference pattern of laser light according to the present invention has an excellent effect that it can be adopted as a mass production technique for a multilayer structure with high accuracy. .

[Brief description of the drawings]

FIG. 1 shows a system for producing a three-dimensional periodic grating structure by combining a method (I) for obtaining a two-dimensional lattice structure by interference of three light beams and a method (II) for obtaining a one-dimensional periodic structure by interference of two light beams.

FIG. 2 shows a method of forming, in a photosensitive resin layer, an image corresponding to a lattice structure constituting a three-dimensional photonic crystal structure based on an interference pattern (a) of four light beams. (B) and (c) are three-dimensional close-packed lattice structures

FIG. 3 is a method for obtaining a one-dimensional periodic structure by two-beam interference.

FIG. 4 is an electron micrograph of a one-dimensional periodic structure

FIG. 5 is a lattice structure having a periodic refractive index in a two-dimensional direction.

FIG. 6 is an electron micrograph of a two-dimensional lattice structure (due to two exposures with two laser beams).

FIG. 7 shows a method of forming a two-dimensional lattice structure using three-beam interference.

FIG. 8 is an electron micrograph of a two-dimensional lattice structure (using three laser beams).

FIG. 9 shows an absorption spectrum of a photocurable resin used as one embodiment.

FIG. 10 is an electron micrograph of a three-dimensional close-packed lattice structure (3
An image corresponding to a one-dimensional periodic structure caused by interference of two-beam laser light was synthesized with an image corresponding to a two-dimensional lattice structure caused by interference of a laser beam of light. )

[Explanation of Signs] BS Beam Splitter M Mirror

Claims (5)

[Claims] An image corresponding to a lattice structure forming a photonic crystal structure is formed by irradiating a light beam obtained by dividing a single laser beam into a plurality of photosensitive resin layers at an angle to each other into a photosensitive resin layer by laser interference. A method for forming a lattice structure of a photonic crystal by laser interference using a photosensitive resin, including a step of forming the photonic crystal in a conductive resin layer. 2. The method for forming a lattice structure of a photonic crystal by laser interference according to claim 1, wherein the material constituting the photosensitive resin layer is a photocurable resin. 3. The step of forming an image corresponding to a lattice structure constituting a photonic crystal structure in the photosensitive resin layer by interference of a laser beam is performed by interference of a light beam obtained by dividing one laser into three. The image forming apparatus according to claim 1, wherein the image is formed by combining an image corresponding to a two-dimensional lattice structure and an image corresponding to a one-dimensional periodic lattice structure by interference of a light beam obtained by dividing one laser beam into two. A method of creating a close-packed lattice structure of a photonic crystal by laser interference. 4. A step of forming an image corresponding to a lattice structure constituting a photonic crystal structure in a photosensitive resin layer by interference of a laser beam includes dividing one laser beam from one light source into three. It is formed by combining an image corresponding to a two-dimensional lattice structure due to light beam interference and an image corresponding to a one-dimensional periodic structure due to interference of light beams obtained by dividing one laser beam from the other light source into two. 4. The method for producing a close-packed lattice structure of a photonic crystal by laser interference according to claim 3, wherein: 5. The step of forming an image corresponding to a lattice structure constituting a photonic crystal structure in a photosensitive resin layer by interference of a laser beam is performed by interference of a light beam obtained by dividing one laser into four. The method for producing a close-packed lattice structure of a photonic crystal by laser interference according to claim 1 or 2, wherein: