JP4956805B2 - 3D photonic crystal manufacturing method and 3D photonic crystal manufacturing apparatus used therefor - Google Patents

Description

  The present invention relates to a method of manufacturing a three-dimensional photonic crystal, which is an optical medium for manufacturing various optical waveguide devices using a photonic band gap, and various optical devices using optical characteristics at the band edge, and to be used in the method. It relates to a manufacturing apparatus.

  In recent years, a photonic crystal has been proposed as a new optical medium for manufacturing various optical devices. This photonic crystal has a periodic refractive index distribution in the wavelength order of light, and has a feature that a band structure is formed with respect to photon energy. In particular, in the case of a three-dimensional photonic crystal having a refractive index profile with a three-dimensional period, a complete photonic band gap is formed in which light is prohibited in all directions. By allowing the existence of the optical waveguide, it is possible to form a very small optical waveguide, and it is possible to form a micro optical resonator by introducing a point defect and allowing light to be captured at a minute point. As a result, the fundamental control of the waveguide phenomenon and the light emission phenomenon can be performed, and the performance of various light emitting devices can be improved. In addition, paying attention to the band edge where the group velocity of light becomes zero, using a standing wave state as a resonator realizes a large area laser, etc. It is also expected that various light controls will be possible based on unique dispersion relationships.

  The three-dimensional photonic crystal manufacturing method is roughly classified into four methods. The first manufacturing method is a method using agglomeration of fine particles. In this method, for example, when plastic spheres with a diameter of several microns are dispersed in water and left to stand to evaporate the water, the plastic spheres form the most stable face-centered cubic lattice in terms of energy. . However, according to the first manufacturing method, a misaligned defect is likely to enter a part of the formed crystal, but there is a problem that there is no method for artificially introducing a defect into a waveguide. Another problem is that the crystals that can be formed are limited to the face-centered cubic lattice.

  The second manufacturing method is a layer-by-layer formation method. In this method, a two-dimensional lattice is formed by etching and stacked to form a three-dimensional structure, or two types of materials having different refractive indexes are alternately formed on a substrate on which a two-dimensional lattice is formed in advance. It is made three-dimensional by stacking. However, according to the second manufacturing method, it is easy to introduce artificial defects during the formation of the crystal, but it takes time to form the crystal, so it is difficult to form a large crystal with a large number of atomic layers. There is a problem.

  The third manufacturing method is a SOR (Synchrotron Orbital Radiation) lithography method. In this method, a face-centered cubic lattice is formed by multiple exposure from three directions with obliquely incident X-rays using a triangular array of two-dimensional X-ray masks. However, this third manufacturing method has a problem that the production is expensive because the SOR is used in addition to the face-centered cubic lattice that has been reported in the past.

  The fourth manufacturing method is a laser interference method called a holographic lithography method (see, for example, Patent Document 1). In this method, one laser beam is divided into four light beams, and these four light beams are simultaneously interfered in the photo-curable resin by one exposure. Then, since periodic interference fringes are formed and the photo-curing resin in the portion is cured, if the uncured portion is removed, only the cured portion having the three-dimensional lattice structure remains. According to this method, it has been proved that all 14 types of Bravey lattices can be formed by using four-beam interference, and a method for introducing artificial defects has also been proposed, so that relatively large crystals can be formed. It can be a powerful technique.

JP 2000-329920 A

  However, among the conventional manufacturing methods of three-dimensional photonic crystals, the fourth manufacturing method has a problem that the optical system for four-beam interference is complicated and it is difficult to configure the optical system depending on the crystal system to be formed. is there. Further, in interference, the contrast of interference fringes is determined by the inner product between the polarizations of the four light beams. However, because the four light beams are used, for example, the polarization directions cannot be set arbitrarily, as can be seen from the fact that the polarization directions cannot all be matched. There is also a problem.

  The present invention has been made in view of such problems, and in a so-called holographic lithography method for producing a three-dimensional photonic crystal by causing interference fringes by causing a plurality of light beams to interfere in a photosensitive material, Provided is a means for manufacturing a large-scale photonic crystal in a short time using an optical system having a simple configuration, and a manufacturing apparatus used therefor.

The method for producing a three-dimensional photonic crystal according to claim 1 for achieving the above object is characterized in that the method for producing a three-dimensional photonic crystal whose refractive index changes in a three-dimensional period is refracted in accordance with the intensity of irradiated light. By performing two-beam interference exposure from three different directions on the same surface of the photosensitive material having a variable rate, a latent image group in which a plurality of wall-shaped latent images having a predetermined thickness are arranged in parallel in the three directions. Each of the three latent image groups is formed toward each other, and a difference in refractive index is generated between the portion where these three latent image groups overlap and the other portion, thereby forming a three-dimensional period refractive index change in the photosensitive material.

  3. The method for producing a three-dimensional photonic crystal according to claim 2, wherein the two-beam interference exposure from three different directions with respect to the photosensitive material is performed two times with a predetermined time difference with respect to the photosensitive material at a predetermined time. Light beam interference exposure is performed, and the photosensitive material is rotated by a predetermined angle within the same plane between each two light beam interference exposures.

  4. The method of manufacturing a three-dimensional photonic crystal according to claim 3, wherein two-beam interference exposure from three different directions with respect to the photosensitive material is performed three times with a predetermined time difference at different incident angles with respect to the photosensitive material. Light beam interference exposure is performed, and the photosensitive material is rotated by a predetermined angle within the same plane between each two light beam interference exposures.

5. The three-dimensional photonic crystal manufacturing apparatus according to claim 4, wherein the light intensity changes periodically in the three-dimensional photonic crystal manufacturing apparatus for manufacturing a three-dimensional photonic crystal whose refractive index changes in a three-dimensional cycle. The optical system for creating a light field by two-beam interference exposure, and the photosensitive system so that the two-beam interference exposure is performed by the optical system on the surface of the photosensitive material whose refractive index changes according to the intensity of the irradiated light. And a movable stage that holds the material rotatably in the same plane.

  In the three-dimensional photonic crystal manufacturing apparatus according to claim 5, the optical system is provided so that an incident angle of the two-beam interference exposure to the photosensitive material can be changed.

  According to the method for producing a three-dimensional photonic crystal according to the present invention, three wall groups are formed on a photosensitive material by performing two-beam interference exposure from three different directions, so that an optical system with a simple configuration can be used. A large three-dimensional photonic crystal can be formed in a short time. Further, since the two-beam interference exposure is performed from three different directions by rotating the photosensitive material without moving the optical system, the configuration of the optical system can be further simplified.

  Also, by using two-beam interference exposure, the polarization direction can be made the same, so that interference fringes with a high contrast can be formed. On the contrary, the contrast can be adjusted by changing the polarization direction and the intensity ratio, and it is possible to control the connection and shape of the atoms.

  Further, by changing the incident angle to the photosensitive material for each two-beam interference exposure, other than cubic system, that is, tetragonal system, orthorhombic system, rhombohedral system, hexagonal system, monoclinic system, 3 It is also possible to form an oblique lattice. Accordingly, all 14 types of Bravay lattices can be formed together with the case where a cubic lattice is formed with a constant incident angle to the photosensitive material.

  In addition, according to the three-dimensional photonic crystal manufacturing apparatus according to the present invention, a light field whose light intensity changes periodically is generated by two-beam interference exposure. A three-dimensional photonic crystal can be formed. Further, by controlling the movable stage and rotating the photosensitive material in the same plane, two-beam interference exposure can be performed from different directions of the photosensitive material without moving the optical system.

  Further, according to the three-dimensional photonic crystal manufacturing apparatus according to the present invention, the incident angle to the photosensitive material is changed every three two-beam interference exposures, so that other than the cubic system, that is, the tetragonal system, the oblique system, and the like. It is also possible to form a tetragonal, rhombohedral, hexagonal, monoclinic or triclinic lattice. Accordingly, all 14 types of Bravay lattices can be formed together with the case where a cubic lattice is formed with a constant incident angle to the photosensitive material.

Hereinafter, a method for manufacturing a three-dimensional photonic crystal and an apparatus for manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating the configuration of a three-dimensional photonic crystal manufacturing apparatus 1 according to the present embodiment. The three-dimensional photonic crystal manufacturing apparatus 1 includes an optical system 2 that generates a light field whose light intensity changes in a space with a period in the order of the wavelength of light, and a photosensitive material in the light field generated by the optical system 2. And a movable stage 4 that rotatably holds 3.

  The optical system 2 is a so-called two-beam interference exposure system, and as shown in FIG. 1, a laser light source 5 that emits a laser beam L1 and a laser beam L1 emitted from the laser light source 5 into two beam L2, A beam splitter 6 for dividing the light beam L3, an optical path mirror group 7 for guiding the light beams L2 and L3 to the photosensitive material 3 on the movable stage 4, and a beam extender for expanding the beam diameter of the light beams L2 and L3. A panda 8 and an optical path length correction mechanism 9 for correcting the optical path length of one of the two light beams L2 and L3 are provided.

  The laser light source 5 includes a shutter device 10 and can control the shutter device 10 to emit laser light L1 at a desired timing. The beam splitter 6 includes a so-called half mirror 11, and the half mirror 11 reflects or transmits the laser light L1 into two parts. The beam expander 8 includes a condenser lens 12, a spatial filter 13, and a collimating lens 14, and condenses the light beams L <b> 2 and L <b> 3 by the condenser lens 12 and is formed in the spatial filter 13. Then, the beam diameter is expanded by converting it into parallel light by the parallelizing lens 14. The optical path length correction mechanism 9 is disposed on the optical path of the light beam L2 reflected by the half mirror 11, and corrects the optical path length appropriately in relation to the optical path length of the light beam L3 transmitted through the half mirror 11. It is.

  According to the optical system 2 configured as described above, one laser light L1 emitted from the laser light source 5 is guided to the beam splitter 6 by the optical path mirror 7A and is divided into two light beams L2 and L3. Of these, the light beam L3 that has passed through the half mirror 11 is guided to the beam expander 8 by the optical path mirror 7B, the beam diameter is expanded, and then reflected by the optical path mirror 7C to irradiate the movable stage 4. Is done. On the other hand, the light beam L2 reflected by the half mirror 11 is expanded in beam diameter by the beam expander 8, and its optical path length is corrected by the optical path length correction mechanism 9, and then reflected by the optical path mirror 7D. 4 is irradiated. Thereby, in the space near the movable stage 4, the light beam L3 from the optical path mirror 7C and the light beam L2 from the optical path mirror 7D intersect at a predetermined angle, and due to the interference, periodic interference fringes, that is, the wavelength order of light. A light field whose light intensity changes with a period of is created.

  On the other hand, the movable stage 4 is not shown in detail in the figure, but a holding tray for holding the photosensitive material 3 in the light field created by the optical system 2 and the photosensitive material 3 centered on the normal line. The rotary stage is rotatably supported.

  Hereinafter, a method for manufacturing a three-dimensional photonic crystal using the three-dimensional photonic crystal manufacturing apparatus 1 will be described. First, the photosensitive material 3 is set on the movable stage 4. In this embodiment, as the photosensitive material 3, a photocurable resin that is cured by being exposed with a light intensity equal to or higher than a certain threshold is used, and the photosensitive material 3 is applied onto a predetermined substrate, whereby 3 thin film is formed. Then, the substrate on which the thin film of the photosensitive material 3 is formed is fixed on the movable stage 4 so as not to move.

  Next, the shutter device 10 is operated to perform the first exposure from the laser light source 5. As described above, the laser light L1 emitted from the laser light source 5 is divided into two light beams L2 and L3 by the beam splitter 6, and the light beam L3 transmitted through the half mirror 11 passes through the beam expander 8 and is reflected by the reflecting mirror 7C. The light beam L2 reflected by the half mirror 11 is reflected by the reflecting mirror 7D via the beam expander 8 and the optical path length correcting mechanism 9, thereby being reflected on the movable stage 4 at a predetermined incident angle. The photosensitive material 3 is exposed. The two light beams L2 and L3 intersect with each other in the photosensitive material 3 to form periodic interference fringes, and the photosensitive material 3 is exposed to a portion corresponding to the interference fringes to form a so-called latent image. is doing. As a result, as shown in FIG. 2A, a latent image group 17 in which wall-shaped latent images 16 having a predetermined thickness are arranged in parallel at a predetermined interval is formed in the photosensitive material 3 in a predetermined direction. The

  Then, after the first exposure is finished, the photosensitive material 3 is rotated by a predetermined angle by controlling the operation of the movable stage 4. More specifically, when an orthogonal coordinate system of (X, Y, Z) is considered in the space with the position of the photosensitive material 3 as the origin, the photosensitive material 3 is rotated by 120 ° around the Z axis in the XY plane. In this state, the shutter device 10 is operated to perform the second exposure from the laser light source 5, and the two light fluxes L2 and L3 are exposed to the photosensitive material 3 at the same incident angle as in the first exposure. As a result, periodic interference fringes are formed in the photosensitive material 3, and as shown in FIG. 2B, a latent image group 18 extending in a direction different from that at the time of the first exposure is formed. The

  Further, after the second exposure is completed, the operation of the movable stage 4 is again controlled to rotate the photosensitive material 3. More specifically, the photosensitive material 3 is rotated by 120 ° around the Z axis in the XY plane and in the same direction as the direction rotated between the first exposure and the second exposure. From this state, the shutter device 10 is operated to perform the third exposure from the laser light source 5, and the two light beams L2 and L3 are exposed to the photosensitive material 3 at the same incident angle as the first and second times. . As a result, periodic interference fringes are formed in the photosensitive material 3, and as shown in FIG. 2C, a latent image group extending in a direction different from that in the first and second exposures. 19 is formed.

  Finally, the photosensitive material 3 is developed using a solvent or the like. That is, when the third exposure is completed, three latent image groups 17, 18, and 19 extending in three different directions are formed in the photosensitive material 3, and these three latent image groups 17, 18, and 19 are formed. In the portion where 19 overlaps, the exposure amount exceeds the threshold value of the photosensitive material 3 after three exposures. As a result, the photosensitive material 3 is cured only in the portion where the three latent image groups 17 overlap, and the other portions remain uncured. Therefore, if the uncured portion is removed using a solvent or the like, the photosensitive material 3 is left in a hollow state with only the cured portion remaining. As a result, a three-dimensional photonic crystal that forms a three-dimensional period refractive index change between the remaining portion of the photosensitive material 3 and the air in the cavity is obtained. In this embodiment, by appropriately setting the incident angles of the two light beams L2 and L3 to the photosensitive material 3, as shown schematically in FIG. 3, the cured portion 20 of the photosensitive material 3, that is, the three latent image groups 17 are provided. A three-dimensional photonic crystal having a face-centered cubic lattice is formed such that the overlapping portion is located at a position corresponding to a lattice point of the face-centered cubic lattice. 3 shows a state in which the respective hardened portions 20 are coupled to each other via a rod-shaped connecting member 21, this connecting member 21 is merely shown for convenience of explanation. Actually, the connecting member 21 is not formed, and the cured portions 20 have a large diameter so as to come into contact with each other, and the cured portions 20 are coupled to each other through the contact portions.

  In this embodiment, two-beam interference exposure is performed three times without changing the incident angles of the light beams L2 and L3 to the photosensitive material 3, and the photosensitive material 3 is moved around the Z axis in the XY plane between the exposures. A three-dimensional photonic crystal having a face-centered cubic lattice was formed by rotating 120 ° at a time. However, if the incident angle of the light beams L2 and L3 to the photosensitive material 3 and the rotation angle of the photosensitive material 3 are appropriately changed, a simple cubic is obtained. It is also possible to form cubic lattices such as lattices and body-centered cubic lattices. Further, in addition to rotating the photosensitive material 3 between each exposure, if the incident angles of the light beams L2 and L3 to the photosensitive material 3 are appropriately changed for each exposure, other than the cubic system, that is, a tetragonal crystal , Orthorhombic, rhombohedral, hexagonal, monoclinic and triclinic lattices can be formed. Thus, according to the present invention, it is possible to form all 14 types of Bravais lattices.

  Further, according to the present embodiment, since the photosensitive material 3 is rotated around the Z axis in the XY plane, the formed grating is limited to a specific orientation, but the photosensitive material 3 is, for example, the Y axis and the Z axis. It is possible to form a lattice having an arbitrary orientation by rotating around the two axes.

  Further, as a means for forming the three latent image groups 17 inside the photosensitive material 3, for example, the optical system 2 is movably provided in addition to a method of rotating the photosensitive material 3 between exposures, and the photosensitive material 3 is provided. A method of moving the optical system 2 between exposures while fixing the position of 3 and a method of switching the optical system 2 between exposures by providing a plurality of optical systems 2 while fixing the position of the photosensitive material 3 are also adopted. Is possible. However, rotating the photosensitive material 3 as in this embodiment has an advantage that the configuration of the optical system 2 can be simplified.

Further, in this embodiment, the so-called negative photosensitive material 3 in which the exposed portion is cured is used, but a so-called positive photosensitive material 3 in which the exposed portion is decomposed can be used instead. It is. In this case, if the photosensitive material 3 is decomposed only in a portion where the three wall- like latent image groups overlap, and the decomposed portion is removed with a solvent or the like, the photosensitive material 3 corresponds to a lattice point of a three-dimensional lattice. The position to do is a hollow state. As a result, a three-dimensional photonic crystal that forms a change in refractive index with a three-dimensional period between the remaining portion of the photosensitive material 3 and the air in the hollow portion is obtained.

  Instead of performing two-beam interference exposure on the photosensitive material 3, X-ray irradiation is performed three times on an X-ray resist material typified by acrylic resin, and the acrylic resin is appropriately rotated between each irradiation. It is also possible to make it. In this case, if exposure is made through a slit array X-ray mask so that a hole is opened in the acrylic resin only in a portion where each X-ray overlaps, a three-dimensional period of refraction occurs in the residual portion of the acrylic resin and the portion where the hole is opened. A three-dimensional photonic crystal forming a rate change is obtained.

  The present invention is applicable to the production of various optical waveguide devices using a photonic band gap and various optical devices using optical characteristics at the band edge.

Schematic which shows the structure of the three-dimensional photonic crystal manufacturing apparatus 1 which concerns on a present Example. FIG. 3 is an explanatory diagram for explaining three latent image groups 17, 18, and 19 formed in the photosensitive material 3. Explanatory drawing for demonstrating the three-dimensional photonic crystal of a face-centered cubic lattice.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3D photonic crystal manufacturing apparatus 2 Optical system 3 Photosensitive material 4 Movable stage 16 Latent image 17, 18, 19 Latent image group 20 Curing part of photosensitive material L2, L3 Light beam

Claims (5)

In the method of manufacturing a three-dimensional photonic crystal whose refractive index changes with a three-dimensional period,
By performing two-beam interference exposure from three different directions on the same surface of the photosensitive material whose refractive index changes according to the intensity of the irradiated light, a plurality of wall-like latent images having a predetermined thickness are arranged in parallel. Each of the latent image groups is formed in the three directions, and a difference in refractive index is produced between the portion where the three latent image groups overlap and the other portion, thereby refraction of the photosensitive material in a three-dimensional period. A method for producing a three-dimensional photonic crystal, characterized by forming a rate change.   In the two-beam interference exposure from three different directions on the photosensitive material, the two-beam interference exposure is performed three times with the same incident angle and a predetermined time difference on the photosensitive material. The method for producing a three-dimensional photonic crystal according to claim 1, wherein the photosensitive material is rotated by a predetermined angle in the same plane.   In the two-beam interference exposure from three different directions on the photosensitive material, the two-beam interference exposure is performed three times with a predetermined time difference at different incident angles on the photosensitive material, and the two-beam interference exposure is performed between each two-beam interference exposure. The method for producing a three-dimensional photonic crystal according to claim 1, wherein the photosensitive material is rotated by a predetermined angle in the same plane. In a three-dimensional photonic crystal manufacturing apparatus for manufacturing a three-dimensional photonic crystal whose refractive index changes with a three-dimensional period,
An optical system that creates a light field whose light intensity changes periodically by two-beam interference exposure;
A movable stage that rotatably holds the photosensitive material in the same plane so that two-beam interference exposure is performed by the optical system on the surface of the photosensitive material whose refractive index changes according to the intensity of the irradiated light. And a three-dimensional photonic crystal manufacturing apparatus.   The three-dimensional photonic crystal manufacturing apparatus according to claim 4, wherein the optical system is provided so as to change an incident angle to the photosensitive material in two-beam interference exposure.

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