WO2006103938A1 - Photonic crystal and method for producing same - Google Patents

Photonic crystal and method for producing same Download PDF

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Publication number
WO2006103938A1
WO2006103938A1 PCT/JP2006/305207 JP2006305207W WO2006103938A1 WO 2006103938 A1 WO2006103938 A1 WO 2006103938A1 JP 2006305207 W JP2006305207 W JP 2006305207W WO 2006103938 A1 WO2006103938 A1 WO 2006103938A1
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Prior art keywords
photonic crystal
nonlinear optical
layer
dimensional
crystal layer
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PCT/JP2006/305207
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French (fr)
Japanese (ja)
Inventor
Shinichiro Inoue
Yoshinobu Aoyagi
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Riken
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Priority to JP2007510380A priority Critical patent/JP4875611B2/en
Publication of WO2006103938A1 publication Critical patent/WO2006103938A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/35—Non-linear optics
    • G02F1/365—Non-linear optics in an optical waveguide structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/1225—Basic optical elements, e.g. light-guiding paths comprising photonic band-gap structures or photonic lattices
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2202/00—Materials and properties
    • G02F2202/32—Photonic crystals

Definitions

  • the present invention relates to a photonic crystal and a manufacturing method thereof, and more specifically, to a photonic crystal including a nonlinear optical material at least in part and a manufacturing method thereof.
  • ⁇ Cock crystal '' means a material that includes at least two materials having different refractive indexes, and that at least two materials having different refractive indexes form a structure having a periodic structure. Shall. Therefore, as long as at least a part of the structure including the periodic structure is included, the presence or type of the structure other than the structure having the periodic structure is not asked. It shall be included in “crystal”.
  • the “photonic crystal” in the present specification means the structure itself having the periodic structure described above, and includes the structure having the periodic structure described above. It shall mean a larger structure.
  • the above-described semiconductor light emitting device that generates a laser beam having a wavelength in the deep ultraviolet region or the infrared region has not yet been realized.
  • LD compact visible semiconductor laser diode
  • the wavelength conversion element that performs wavelength conversion by the nonlinear optical effect for example, a wavelength conversion element using an angle (or temperature) phase matching method using birefringence of a bulk nonlinear optical crystal, or a periodic conversion to a nonlinear optical crystal.
  • Pseudo phase matching wave with polarization reversal Long conversion elements are known.
  • the wavelength conversion element based on the angle (or temperature) phase matching method is limited to nonlinear optical crystals with low refractive index wavelength dispersion and high birefringence, and the progress of incident light and converted light.
  • the conversion efficiency is inferior because there is a misalignment in the direction (walk-off), misalignment of the incident light when condensing, and the use of diagonal components with a high nonlinear optical coefficient cannot be used. was there.
  • the angle (or temperature) phase matching method requires a large angle precision adjustment mechanism and a temperature modulator in principle, and as a result, there is a problem that the entire element size cannot be reduced.
  • a wavelength conversion element using the quasi-phase matching method can reduce the cross-sectional area because the element can be processed into an optical waveguide shape, and a very strong light intensity can be obtained even if the input power is not so high.
  • advantages such as maintaining high light intensity over the entire length of the crystal, but compared to ideal phase matching, the rate of increase in conversion efficiency relative to the interaction length.
  • problems such as being difficult to perform with high accuracy and being limited to materials that are ferroelectric and easily reverse polarization.
  • the performance depends on the nonlinear optical coefficient of the crystal, and the strength of the interaction itself cannot be increased.
  • photonic crystals having a structure having a periodic structure in which at least two kinds of substances having different refractive indexes with a period of about the light wavelength are arranged one-dimensionally, two-dimensionally or three-dimensionally are attracting attention.
  • This photonic crystal is an artificial optical nanostructure with a structure in which the refractive index is periodically changed on the scale of the light wavelength, and is extremely low, a few tenths of the speed of light in vacuum. It is known that the group speed of light can be realized slowly (see Non-Patent Document 1), and such photonic crystals are expected to be applied to nonlinear fields. Technical proposals are highly desired.
  • Non-Patent Document l Phys. Rev. B 69, 205 109 1 -6 (2004)
  • the present invention has been made in view of the various needs as described above with respect to the prior art, and an object of the present invention is to provide a photonic crystal excellent in nonlinear optical characteristics and a method for manufacturing the same. It is something to try.
  • the present invention provides a photonic crystal containing a nonlinear optical material and a manufacturing method for producing the photonic crystal with high accuracy. If the fabrication of photonic crystals containing nonlinear optical materials is realized with high accuracy, a new ⁇ -type phase matching can be realized, and the efficiency of various nonlinear optical operations can be improved compared to the conventional operating principle. It becomes possible to improve.
  • the conversion efficiency to the harmonic increases in proportion to the square of the electric field amplitude.
  • the photonic crystal that increases the electric field intensity of light as described above, it is expected that the performance of the second harmonic generation will be dramatically improved.
  • the wavelength conversion element in addition to the increase in the electric field intensity of the light described above, it is important to match the phase between the incident laser beam (fundamental wave) and the harmonic (phase matching).
  • the photonic crystal the light dispersion relationship can be freely designed, and according to the present invention, phase matching can be achieved by a completely different method from the conventional one. This Since the phase matching technology using the tonic crystal satisfies the ideal phase matching condition, the conversion efficiency does not decrease like the pseudo phase matching.
  • phase matching and low group velocity can be realized, and the nonlinear optical characteristics can be remarkably improved.
  • a photonic crystal part including an inorganic nonlinear optical crystal and providing a periodic refractive index distribution structure is provided between upper and lower cladding regions.
  • the present invention has a cladding region on the top and bottom, and has one or more core layer portions for guiding light between the top and bottom cladding regions, and the top and bottom At least a part of the cladding region or the core layer portion includes a photonic crystal portion that gives a periodic refractive index distribution structure, and an inorganic nonlinear optical crystal is formed on at least a part of the upper and lower cladding regions or the core layer portion. It is what you have.
  • the present invention has a cladding region on the top and bottom, and has one or more core layer portions for guiding light between the top and bottom cladding regions, and the top and bottom At least a part of the cladding region or the core layer part includes a one-dimensional or two-dimensional photonic crystal layer, and an inorganic nonlinear optical crystal layer is formed on the upper and lower cladding regions or the core layer part. It is made to have.
  • the present invention also provides a cladding layer, an inorganic nonlinear optical crystal layer formed on the cladding layer, and a one-dimensional or two-dimensional photonic crystal formed on the inorganic nonlinear optical crystal layer. And a layer.
  • the present invention is such that, in the above-described invention, the thickness of the inorganic nonlinear optical crystal layer is a thickness at a wavelength level of light.
  • the thickness of the inorganic nonlinear optical crystal layer is 5 Onm to LO ⁇ m.
  • the present invention is the above-described invention, wherein the inorganic nonlinear optical crystal layer has a thickness of 2 OOnm to l ⁇ m.
  • the inorganic nonlinear optical crystal layer is formed into a thin film shape by polishing the surface of the inorganic nonlinear optical crystal.
  • the present invention provides the above-described invention in which the one-dimensional or two-dimensional photonic crystal layer is Is formed of a SiO-based material, a glass-based material, or a polymer material.
  • the inorganic nonlinear optical crystal constituting the inorganic nonlinear optical crystal layer is a LiNbO crystal.
  • the present invention provides a method for producing a photonic crystal having nonlinear optical characteristics, the first step of forming an inorganic nonlinear optical crystal layer on a cladding layer, and the inorganic nonlinear optical crystal layer on the inorganic nonlinear optical crystal layer. And a second step of forming a one-dimensional or two-dimensional photonic crystal layer.
  • the inorganic nonlinear optical crystal layer is formed to have a thickness at a wavelength level of light.
  • the thickness of the inorganic nonlinear optical crystal layer is formed to be 50 nm to 10 m.
  • the thickness of the inorganic nonlinear optical crystal layer is set to 200 ⁇ ! It is designed to form ⁇ 1 ⁇ m.
  • the inorganic nonlinear optical crystal is surface-polished to form the inorganic nonlinear optical crystal layer in a thin film shape.
  • the second step includes: a SiO-based material, glass
  • the one-dimensional or two-dimensional photonic crystal layer is formed of a system material or a polymer material.
  • the present invention is the above invention, wherein the second step is performed by using a LiNbO crystal.
  • the inorganic nonlinear optical crystal layer is formed.
  • the material for forming the one-dimensional or two-dimensional photonic crystal layer is disposed on the inorganic nonlinear optical crystal layer.
  • a one-dimensional or two-dimensional photonic crystal layer is formed by forming a periodic structure for the material by nanoimprint lithography.
  • FIGS. 1 (a), (b), (c), (d), (e), (f), (g), (h), and (i) show the processing procedure of the photonic crystal manufacturing method according to the present invention. It is explanatory drawing.
  • FIG. 2 is a cross-sectional perspective view of a conceptual configuration of a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure.
  • Fig. 3 is a SEM (scanning electron microscope) photograph of the cross section of a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i). It is explanatory drawing which shows a state.
  • Fig. 4 shows the photonic band structure obtained by the theory and experiment obtained for a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i). It is a graph which shows.
  • Fig. 5 shows a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i).
  • Fig. 6 shows a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i). It is a graph which shows the result of having observed the generation
  • FIG. 7 is an explanatory diagram showing a configuration example when wavelength conversion is performed using a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure.
  • FIG. 8 is an explanatory diagram of a photonic crystal manufacturing method according to the present invention when nanoimprint lithography technology is applied to the fabrication.
  • FIG. 9 is an explanatory view showing the state of an electron micrograph of a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure manufactured by the manufacturing method shown in FIGS. 8 (a) to (i). is there
  • FIG. 10 shows a nonlinear two-dimensional photonic crystal manufactured by the manufacturing method shown in (a) to (i). It is a graph which shows the measurement result by the angle scanning reflection spectroscopy of the photonic crystal provided with the waveguide structure.
  • Substrate consisting of 16 'LiNbO thin film and SiO film
  • a LiNbO crystal which is the most typical inorganic nonlinear optical crystal, is used as a nonlinear optical material.
  • Waveguide with original photonic crystal structure hereinafter referred to as ⁇ nonlinear two-dimensional photonic crystal waveguide '' It will be appropriately referred to as “road”. The case where a photonic crystal having the structure of) is produced will be described.
  • JP-A-2004-133429 describes an element structure and a manufacturing method for realizing a nonlinear two-dimensional photonic crystal waveguide that is a two-dimensional photonic crystal waveguide mainly using a nonlinear optical material.
  • a nonlinear optical material an organic nonlinear optical polymer is used as a nonlinear optical material
  • a metal cladding specifically, silver
  • a periodic structure is used.
  • the SiO film 14 used as a cladding layer is about 4 / zm thick by plasma CVD.
  • a film-formed substrate 16 is produced (see FIG. 1 (b)).
  • the thickness of the adhesive layer 20 is set to about 0.3 to 0.5 / zm.
  • the thickness of the LiNbO single crystal wafer 12 is the thickness of the wavelength level of light, for example, 50 nm
  • a substrate made of LiNbO thin film 12 'and SiO film 14 is indicated by reference numeral 12'.
  • polishing process by the polishing machine described above is performed according to the procedure shown in the following processes 1 to 4.
  • LiNbO single crystal wafer 12 with a thickness of about Lmm is about 0.05mm thick
  • This step 1 is performed by a horizontal grinding machine.
  • Step 2 is performed by a high speed lapping machine.
  • This step 3 is performed by a high speed lapping machine.
  • Process 4 Finish polishing with SiO slurry
  • a LiN bO thin film 12 which is an inorganic nonlinear optical crystal layer, is obtained.
  • This step 4 is performed by an Oscar polisher.
  • a two-dimensional photonic crystal structure consisting of a periodic structure with high perpendicularity and high aspect ratio is formed on the polished surface 12'a of film 12 'by electron beam lithography and ICP dry etching using reactive gas.
  • the two-dimensional photonic crystal layer 28 (see FIG. 1 (i)) is formed.
  • PMMA22 for forming the two-dimensional photonic crystal layer 28 is spin-coated to a thickness of about 300 nm to 1 / ⁇ ⁇ , baked at about 100 to 180 ° C, and then for dry etching.
  • a two-dimensional periodic pattern consisting of the desired periodic structure is drawn by electron beam lithography using an electron beam exposure system (see Fig. 1 (g)).
  • a hole pattern with a diameter of about 200 nm was patterned into a square lattice with a period of about 500 nm.
  • the pattern was transferred to the hard mask material 24 by dry etching using a fluorine-based reactive gas, and then applied to PMMA 22 by dry etching using an O ZAr reactive gas.
  • the photonic crystal structure is processed with high accuracy (see Fig. 1 (h)).
  • the two-dimensional photonic crystal layer 28 which is a periodic refractive index modulation layer, is formed separately from each other and has a two-layer core structure formed by integrally coupling the two layers.
  • a photonic crystal 10 with a nick crystal waveguide structure could be fabricated (see Fig. L (i)).
  • Fig. 2 shows a cross-sectional perspective view of the conceptual configuration of a photonic crystal 10 having a nonlinear two-dimensional photonic crystal waveguide structure with a square lattice structure and a photonic crystal period of 500 nm fabricated as described above. Has been.
  • Fig. 3 shows a cross-sectional SEM of a photonic crystal 10 with a nonlinear two-dimensional photonic crystal waveguide structure with a photonic crystal period of 500 nm and a square lattice structure fabricated as described above ( Scanning electron microscope) An explanatory view showing the state of a photograph is shown.
  • the thickness of the adhesive layer 20 is about 30 Onm
  • the thickness of the SiO film is about 4 m
  • the thickness of the LiNbO thin film 12 is about 60 nm.
  • the film thickness of the two-dimensional photonic crystal layer 28 is about 900 nm.
  • a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure using a Li NbO single crystal, which is a difficult-to-work material is used.
  • LiNbO single crystals, etc. that were difficult to use for photonic crystals in the past because of their non-linear optical characteristics and their operational characteristics but poor workability.
  • Inorganic nonlinear optical crystals can be used as photonic crystals It ’s a little tricky.
  • a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure manufactured by a photonic crystal manufacturing method according to the present invention has a second harmonic compared to the conventional technology. It was demonstrated that the generation of U and enhancement was extremely effective as a wavelength conversion element.
  • the theoretical calculation for the photonic crystal 10 was analyzed using a band calculation method based on the three-dimensional FDTD method, which is more accurate than the plane wave expansion method.
  • each polarized parallel beam using a tungsten halogen white light source is focused on a small sample (not turning) part, and the reflection spectrum is measured using a spectroscope and a CCD.
  • the in-plane beam advance angle with respect to the angle and the crystal symmetry axis was scanned, and the photonic band dispersion curve was traced from the frequency shift of the resonance peak appearing in the spectrum.
  • Figure 4 shows the photonic crystal 10 with a nonlinear two-dimensional photonic crystal waveguide structure with a square lattice structure and a photonic crystal period of 500 nm fabricated as described above. Theoretical and experimental photonic band structures are shown.
  • the photon energy shown on the vertical axis in FIG. 4 can be freely changed.
  • the second harmonic By scanning the wavelength and angle of incident light and the beam traveling angle relative to the photonic crystal during the second harmonic generation measurement, the second harmonic output at the energy and momentum that resonates with the position of the photonic band.
  • the intensity of the wave we can quantitatively investigate and confirm the increase associated with the optical band from the identification of the position of the band and the extent of its intensity, and the conditions under which the photonic crystal operates most efficiently, Confirmation can be made.
  • a short pulse OPA short pulse optical parametric amplifier
  • the incident optical system was the same as that used for the above-mentioned angle scanning polarization reflectance measurement.
  • the harmonic component of the excitation light was removed by an interference filter just before the sample was incident.
  • the harmonic detector used a force to be taken into the spectroscope and CCD by a fiber, or a form to be taken into a photomultiplier tube through a bandpass filter, but for this experiment, a CCD was used.
  • Figure 5 shows the results of observing the generation of the second harmonic (400 nm) obtained by the CCD method at an incident wavelength of 800 nm and the second harmonic in the momentum (incident angle) resonating with the photonic band.
  • the result shows that the wave intensity is greatly increased.
  • an intensity increase of 300 times or more with respect to the Balta part was observed.
  • FIG. 6 shows the result of the incident of a 650 nm basic excitation OPA laser on the photonic crystal 10 as another experimental result.
  • a 650 nm basic excitation OPA laser was incident on the photonic crystal 10
  • the generation of strong second harmonics was observed.
  • the external force is a force that makes basic laser light incident and measures the reflected SHG.
  • an optical lens, optical lens, or waveguide is used. It is longer if the fundamental laser light (fundamental wave) is guided in the plane of the nonlinear two-dimensional photonic crystal waveguide structure through direct bonding of a prism, grating, optical fiber, laser element, or a combination thereof. An interaction length can be obtained, and light can be confined in a very small region, so that wavelength conversion can be performed with higher efficiency.
  • the phase matching condition is satisfied by the photo-band structure, the SHG intensity increases in proportion to the square of the distance, and at the same time, an extremely strong increase in conversion efficiency is obtained due to the electric field enhancement effect of the low group velocity band. You will be able to be.
  • a photonic having a nonlinear two-dimensional photonic crystal waveguide structure using a LiNbO crystal, which is a typical nonlinear optical crystal is used.
  • the photonic crystal 10 could be made.
  • the photonic crystal 10 has a SiO film 14 as a cladding layer.
  • Pre-deposited LiNbO crystal wafer 12 is thinned through the polishing process, and then the secondary
  • the original photonic crystal layer 28 is produced using a fine processing technique. Further,. Laser light was incident on the photonic crystal 10 from the outside, second harmonic generation (SHG) was observed, and an increase in SHG intensity due to the effect of the photonic crystal 10 was observed.
  • SHG second harmonic generation
  • Inorganic nonlinear optical crystals represented by three crystals have high nonlinear optical performance and device operation stability, but are less workable for microfabrication processes than semiconductor materials and organic materials. Application was difficult.
  • the inorganic nonlinear optical crystal itself used as the nonlinear optical material can be simply formed into a thin film without requiring processing such as making fine holes.
  • Photonic crystals with a three-dimensional photonic crystal waveguide structure can be manufactured. Therefore, it is possible to realize highly accurate photonic crystals using inorganic nonlinear optical crystals, which are difficult to process materials. It becomes possible.
  • the method for producing a photonic crystal according to the present invention adds fine inorganic nonlinear optical crystals. This eliminates the disadvantage of poor processability for the process.
  • the inorganic nonlinear optical crystal does not need to be finely processed for a fine periodic structure, if a highly workable material is selected for the two-dimensional photonic crystal layer 28, photonics with a very high processing level can be obtained. Crystals can be produced. This avoids useless light scattering and light loss, and also enables devices that are close to theoretical design with less error and processing fluctuations, resulting in extremely high wavelength conversion efficiency. become.
  • the fact that the inorganic nonlinear optical crystal does not have to be finely processed for a fine periodic structure is that any material can be used as the material of the two-dimensional photonic crystal layer 28. It means that the construction method may be used. Of course, this feature allows the processing accuracy to be maximized. However, if a transparent organic material or glass material is used for the two-dimensional photonic crystal layer 28, a fine periodic structure can be obtained. It becomes possible to apply nanoimprint lithography technology to the production. As a result, the manufacturing cost of the photonic crystal can be significantly reduced.
  • FIGS. 8 (a) to (i) are explanatory diagrams of a method for producing a photonic crystal according to the present invention when nanoimprint lithography technology is applied to the production of a fine periodic structure of a two-dimensional photonic crystal layer.
  • . 8 (a), (b), (c), (d), and (e) are used as cladding layers instead of the SiO film 14.
  • a two-dimensional photonic crystal layer 128 (a periodic structure with a high perpendicularity and a high aspect ratio) is fabricated on the 2 'polished surface 12' a using nanoimprint lithography technology. (See Fig. 8 (i)).
  • DR1ZPMMA122 for forming the two-dimensional photonic crystal layer 128 is spin-coated to a thickness of about 300 nm to l ⁇ m and stacked (see FIG. 8 (f)).
  • a release agent silane-based monomolecular film
  • Si mold 130 placed on DR1ZPMMA122 and pressurize while heating (See Fig. 8 (g)).
  • Si mold 130 having a periodic structure in which a hole pattern having a diameter of about 200 nm is patterned into a square lattice having a period of 600 nm is used.
  • the temperature at the time of heating was set to a temperature (50 to 200 ° C.) around the glass transition temperature Tg, and the pattern formed on the Si mold 130 was directly transferred to the DR 1ZPMMA 122 under this temperature condition.
  • the two-dimensional photonic crystal layer 128, which is a periodic refractive index modulation layer, which is a photonic crystal portion having a two-dimensional photonic crystal structure, are formed separately from each other, and the two are integrated with each other.
  • a photonic crystal 100 having a nonlinear two-dimensional photonic crystal waveguide structure with a two-layer core structure formed by coupling was successfully fabricated (see Fig. 8 (i)).
  • FIG. 9 is an explanatory diagram showing the state of an electron micrograph of the photonic crystal 100 having a nonlinear two-dimensional photonic crystal waveguide structure fabricated as described above, and FIG. Shows a graph showing the measurement results by angle scanning reflection spectroscopy.
  • the photonic crystal manufacturing method according to the present invention in which a technique of nanoimprint lithography is applied to the production of the fine periodic structure of the two-dimensional photonic crystal layer, the photonic crystal can be produced at an epoch-making low cost. This makes it possible to achieve high-precision, large-area, large-volume, high-throughput productivity.
  • the formed two-dimensional photonic crystal waveguide structure is Because it is a waveguide, the longest interaction length can be obtained with very strong light intensity by confining the light in a very small area, which is far more advantageous than other structures in terms of the characteristics of the wavelength conversion process. is there.
  • the cladding layer can also be made of a transparent material that does not absorb fundamental waves and harmonics, so there is no problem of absorption even if a long interaction length is taken. .
  • the embodiment described above can be modified as shown in the following (1) to (13).
  • the structure described in the photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure as the photonic crystal according to the present invention is not limited to this, and an appropriate structure is used. Of course, it may be provided.
  • the photonic crystal structure is not limited to two dimensions, and various photonic crystal structures may be provided.
  • the inorganic nonlinear optical crystal may not be formed in a layered form.
  • LiNbO crystal is used as the inorganic nonlinear optical crystal.
  • inorganic nonlinear optical crystals include LiTaO (LT), KH PO (KDP), KTiOPO (KTP), BaB O (BB
  • LiB O LiB O (LBO), BiB O (BIBO), CsLiB O (CLBO), KNbO (KN), etc.
  • the two-dimensional photonic crystal layer is formed of PMMA, but it is needless to say that the present invention is not limited to this.
  • the two-dimensional photonic crystal layer has little light absorption with respect to the wavelength of the incident wave and the outgoing wave to be used, and has good processability to some extent!
  • an inorganic crystal material for example, an inorganic crystal material, an inorganic glass material, a semiconductor material, an organic material (including a polymer;), a combination material thereof, or the like can be appropriately selected and used. Further specific examples include, for example, SiO, glass material, SiO-based coating film, glass-based coating film, Ti
  • Examples include O, A1N, AlGaN, CaF, Al 2 O, and Ga 2 O.
  • an acrylic polymer is used as an adhesive.
  • an organic adhesive an inorganic adhesive, Combinations thereof can be appropriately selected and used, and more specific preferable examples include, for example, epoxy resin, acrylic resin, polyurethane resin, polyimide resin, silicon resin, low melting glass, Water glass or the like can be appropriately selected and used.
  • the force using a Si wafer as the base substrate is not limited to LiNbO single crystal wafer
  • GaAs single crystal substrate SiC single crystal substrate, GaN single crystal substrate, AlO single crystal substrate, etc.
  • a SiO film or an Ag film is used as the cladding layer.
  • the present invention is not limited to this.
  • any material can be used as long as it satisfies the condition that light absorption is small with respect to the wavelength of the incident wave and the outgoing wave to be used.
  • inorganic crystal materials, inorganic glass materials, semiconductor materials, organic materials (including polymers), combinations thereof, and the like can be used.
  • this cladding layer can be etched.
  • a dry etching technique by electron beam lithography and ICP dry etching using a reactive gas or a nanoimprint lithography technique is used as a processing technique for forming the two-dimensional photonic crystal layer.
  • a dry etching technique by electron beam lithography and ICP dry etching using a reactive gas or a nanoimprint lithography technique is used as a processing technique for forming the two-dimensional photonic crystal layer.
  • other dry etching technology, anodizing technology, chemical etching technology, electron beam lithography technology, focused ion beam lithography technology, photon beam lithography technology, selective growth technology or laser processing Technology can be selected and used as appropriate.
  • the photonic crystal according to the present invention is applied to the deep ultraviolet wavelength region and the infrared wavelength region has been described.
  • the present invention is not limited to this V.
  • the visible wavelength range and the X-ray wavelength range can be applied as wavelength conversion technology in other wavelength ranges such as the far-infrared wavelength range and the terahertz wavelength range.
  • the principle of optical parametric amplification is used, even the same incident wavelength can be converted into various wavelengths. Therefore, a tunable laser element can be realized using the photonic crystal according to the present invention.
  • the case where the photonic crystal according to the present invention is applied to wavelength conversion using the nonlinear optical effect has been described.
  • the present invention is not limited to this! Using the characteristics of the photonic crystal, such as the electric field enhancement effect and the controllability of the dispersion relationship, the efficiency of other effects using nonlinear optical effects such as ultrafast optical modulation and optical switching can be significantly improved. .
  • the photonic crystal according to the present invention is not limited to the above-described embodiment, and the vertical relationship of the inorganic nonlinear optical crystal layer in the photonic crystal and the thin core layer other than the photonic crystal layer have this structure.
  • a structure sandwiched between bodies, a structure in which any other layer is laminated on the photonic crystal layer, a structure without a cladding layer, and the like are also included in the scope of the photonic crystal according to the present invention.
  • a waveguide can be formed on the surface of the inorganic nonlinear optical crystal by diffusing Ti or the like, and the undoped layer of the inorganic nonlinear optical crystal itself can be used as a cladding layer. Those having a nick crystal structure are also included in the scope of the present invention.
  • a material with a higher refractive index on the inorganic nonlinear optical crystal for example, TiO
  • the inorganic nonlinear optical crystal functions as a quad layer as well as a wavelength conversion layer.
  • the force with which the inorganic nonlinear optical crystal layer has a wavelength level thickness for example, a thickness of about 50 mm to 10 ⁇ m, preferably about 200 nm to 1 ⁇ m, and more preferably Is between 200 and 600.
  • the present invention includes, for example, a wavelength conversion element, a harmonic generation element, a sum frequency / difference frequency generation element, an optical parametric amplification element, a stimulated Raman scattering element, a four-wave mixing element, a small laser light source, an optical switch element, and an optical bistable element It can be used for various elements such as optical logic operation elements, light modulation elements, and phase conjugate light generation elements. By using these elements, small and highly efficient deep ultraviolet laser light sources and red light sources can be used. Outside laser light source Can be realized.
  • deep ultraviolet laser light sources are highly integrated next-generation DVDs, light sources for optical memory applications, He-Cd lasers for measurement and sterilization. It is expected to be used as a light source to replace mercury lamps for exposure, and as a light source for deep ultraviolet photocatalyst treatment of environmental pollutants such as PCBs. It is also expected to be applied to biomedical applications such as DNA cleavage, laser microscope, and light source for biomolecular fluorescence recognition.

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Abstract

A photonic crystal containing a nonlinear optical material at least partially and its production method, specifically a photonic crystal exhibiting excellent nonlinear optical characteristics and its production method. Upper and lower cladding regions are provided, a core layer for guiding light is provided between the upper and lower cladding regions, a photonic crystal portion providing a periodic refractive index distribution structure is included, at least partially, in the upper and lower cladding regions or the core layer, and an inorganic nonlinear optical crystal is provided, at least partially, in the upper and lower cladding regions or the core layer.

Description

フォトニック結晶およびその製造方法  Photonic crystal and manufacturing method thereof
技術分野  Technical field
[0001] 本発明は、フォトニック結晶およびその製造方法に関し、さらに詳細には、少なくと もその一部に非線形光学材料を含むフォトニック結晶およびその製造方法に関する なお、本明細書において、「フォト ック結晶」とは、屈折率が異なる少なくとも 2種の 材料を含み、かつ、これら屈折率が異なる少なくとも 2種の材料が周期的構造を備え た構造体を形成するようにしたものを意味するものとする。従って、少なくともその一 部に上記した周期的構造を備えた構造体を含む限りは、当該周期的構造を備えた 構造体以外の構造の有無や種類は問うことなぐ全て本明細書における「フォトニック 結晶」に含まれるものとする。換言すれば、本明細書における「フォトニック結晶」とは 、上記した周期的構造を備えた構造体そのものを意味するとともに、また、上記した 周期的構造を備えた構造体を含んで構成されるより大きな構造体をも意味するものと する。  TECHNICAL FIELD [0001] The present invention relates to a photonic crystal and a manufacturing method thereof, and more specifically, to a photonic crystal including a nonlinear optical material at least in part and a manufacturing method thereof. `` Cock crystal '' means a material that includes at least two materials having different refractive indexes, and that at least two materials having different refractive indexes form a structure having a periodic structure. Shall. Therefore, as long as at least a part of the structure including the periodic structure is included, the presence or type of the structure other than the structure having the periodic structure is not asked. It shall be included in “crystal”. In other words, the “photonic crystal” in the present specification means the structure itself having the periodic structure described above, and includes the structure having the periodic structure described above. It shall mean a larger structure.
背景技術  Background art
[0002] 近年、深紫外領域の波長（波長 200nm〜300nm)や赤外領域の波長（2— 10 m)のレーザー光を発生する小型かつ高性能のレーザー光源力 電子産業分野など における応用を目指して種々提案されて 、る。  [0002] In recent years, a small and high-performance laser light source that generates laser light with a wavelength in the deep ultraviolet region (wavelength 200 nm to 300 nm) and a wavelength in the infrared region (2-10 m) Aiming for applications in the electronics industry Various proposals have been made.
ところで、実用レベルにおいては、上記した深紫外領域や赤外領域の波長のレー ザ一光を発生する半導体発光素子は未だ実現されて ヽな ヽので、こうした深紫外領 域や赤外領域の波長のレーザー光を得るためには、高集積化かつ低消費電力化さ れた小型可視半導体レーザーダイオード (LD)からの出力光を、非線形光学効果に より非常に高い効率で波長変換することが必要であった。  By the way, on a practical level, the above-described semiconductor light emitting device that generates a laser beam having a wavelength in the deep ultraviolet region or the infrared region has not yet been realized. In order to obtain a laser beam of high quality, it is necessary to convert the wavelength of the output light from a highly visible and low power consumption compact visible semiconductor laser diode (LD) with a very high efficiency due to the nonlinear optical effect. Met.
ここで、非線形光学効果により波長変換を行う波長変換素子としては、例えば、バ ルク非線形光学結晶の複屈折を利用した角度 (または温度)位相整合法による波長 変換素子や、非線形光学結晶に周期的分極反転を施した擬似位相整合法による波 長変換素子などが知られて 、る。 Here, as the wavelength conversion element that performs wavelength conversion by the nonlinear optical effect, for example, a wavelength conversion element using an angle (or temperature) phase matching method using birefringence of a bulk nonlinear optical crystal, or a periodic conversion to a nonlinear optical crystal. Pseudo phase matching wave with polarization reversal Long conversion elements are known.
し力しながら、これら従来の波長変換素子は、位相整合は取れるものの問題点も多 いことが指摘されていた。  However, it has been pointed out that these conventional wavelength conversion elements can be phase matched but have many problems.
即ち、角度 (または温度)位相整合法による波長変換素子は、屈折率の波長分散 が少なぐかつ、複屈折が大きい非線形光学結晶にその使用が限られ、また、入射 光と変換光との進行方向の角度ずれ (ウォークオフ)や、集光する場合は入射光の整 合角のずれがあり、また、非線形光学係数の高い対角成分を使用することできない ため、変換効率に劣るという問題点があった。さらに、角度 (または温度)位相整合法 は、大きな角度精密調整機構や温度変調器などが原理上必要となり、その結果とし て全体の素子サイズを小さくすることができないという問題点もあった。  In other words, the wavelength conversion element based on the angle (or temperature) phase matching method is limited to nonlinear optical crystals with low refractive index wavelength dispersion and high birefringence, and the progress of incident light and converted light. There is a problem that the conversion efficiency is inferior because there is a misalignment in the direction (walk-off), misalignment of the incident light when condensing, and the use of diagonal components with a high nonlinear optical coefficient cannot be used. was there. Furthermore, the angle (or temperature) phase matching method requires a large angle precision adjustment mechanism and a temperature modulator in principle, and as a result, there is a problem that the entire element size cannot be reduced.
一方、擬似位相整合法による波長変換素子は、光導波路状に素子を加工できるた め断面積を小さくすることができ、し力もそれほど入力パワーが高くなくても非常に強 い光強度が得られ、また、結晶の全長にわたって高い光強度が保てるなどの優位点 はあるが、理想的な位相整合と比較すると相互作用長に対する変換効率の増加率 力 、さぐまた、短波長になると分極反転技術を精度良く行うことが困難であり、さらに は使用する結晶が強誘電体で分極反転がし易い材料に限られるなどの問題点があ つた。また、その性能は、結晶の非線形光学係数に依存し、相互作用の強さそのもの を増大させることはできな 、と 、う問題点もあった。  On the other hand, a wavelength conversion element using the quasi-phase matching method can reduce the cross-sectional area because the element can be processed into an optical waveguide shape, and a very strong light intensity can be obtained even if the input power is not so high. In addition, there are advantages such as maintaining high light intensity over the entire length of the crystal, but compared to ideal phase matching, the rate of increase in conversion efficiency relative to the interaction length. There are problems such as being difficult to perform with high accuracy and being limited to materials that are ferroelectric and easily reverse polarization. In addition, the performance depends on the nonlinear optical coefficient of the crystal, and the strength of the interaction itself cannot be increased.
即ち、上記したような従来の波長変化素子によれば、位相整合条件を満たすことは できるものの現段階以上の大幅な性能向上は望めず、大幅な性能向上にはより非線 形光学定数の高い物質^ iij製するし力ないものであるが、こうした大幅な性能向上を 見込める物質は見当たらないというのが現状であった。  In other words, according to the conventional wavelength change element as described above, although the phase matching condition can be satisfied, a significant performance improvement beyond the present stage cannot be expected, and a higher nonlinear optical constant is required for the significant performance improvement. The material ^ iij made and powerless, but there is currently no material that can be expected to greatly improve performance.
つまり、現状の波長変換素子開発の延長線上においては、画期的な性能向上を実 現することは現実的に困難であり、新しい原理に基づく新規な素子の開発が強く望ま れていた。  In other words, on the extension of the current development of wavelength conversion elements, it is practically difficult to realize breakthrough performance improvements, and the development of new elements based on new principles has been strongly desired.
一方、現在、光波長程度の周期で屈折率の異なる少なくとも 2種の物質を 1次元、 2 次元あるいは 3次元的に配列させた周期的構造を備えた構造体を有するフォトニック 結晶が注目されている。 このフォトニック結晶は、光波長程度のスケールで周期的に屈折率を変化させた構 造を持つ人工光ナノ構造体であり、真空中の光速と比較して数十分の一以下という 極端に遅 、光の群速度を実現することができることが知られて 、て (非特許文献 1参 照）、こうしたフォトニック結晶は非線形分野への応用が期待されており、フォトニック 結晶を利用した各種技術の提案が強く望まれている。 On the other hand, photonic crystals having a structure having a periodic structure in which at least two kinds of substances having different refractive indexes with a period of about the light wavelength are arranged one-dimensionally, two-dimensionally or three-dimensionally are attracting attention. Yes. This photonic crystal is an artificial optical nanostructure with a structure in which the refractive index is periodically changed on the scale of the light wavelength, and is extremely low, a few tenths of the speed of light in vacuum. It is known that the group speed of light can be realized slowly (see Non-Patent Document 1), and such photonic crystals are expected to be applied to nonlinear fields. Technical proposals are highly desired.
非特許文献 l : Phys. Rev. B 69, 205109 1 -6 (2004)  Non-Patent Document l: Phys. Rev. B 69, 205 109 1 -6 (2004)
発明の開示  Disclosure of the invention
発明が解決しょうとする課題  Problems to be solved by the invention
[0004] 本発明は、従来の技術に対する上記したような種々の要望に鑑みてなされたもの であり、その目的とするところは、非線形光学特性に優れたフォトニック結晶およびそ の製造方法を提供しょうとするものである。 [0004] The present invention has been made in view of the various needs as described above with respect to the prior art, and an object of the present invention is to provide a photonic crystal excellent in nonlinear optical characteristics and a method for manufacturing the same. It is something to try.
課題を解決するための手段  Means for solving the problem
[0005] 上記目的を達成するために、本発明は、非線形光学材料を含んだフォトニック結晶 を提供するとともに、それを高精度で作製する製造方法を提供するものである。非線 形光学材料を含むフォトニック結晶の作製が高精度に実現されれば、新し ヽタイプの 位相整合が実現可能であり、またさらに従来の動作原理に比べ様々な非線形光学 動作の効率を向上することが可能となる。 In order to achieve the above object, the present invention provides a photonic crystal containing a nonlinear optical material and a manufacturing method for producing the photonic crystal with high accuracy. If the fabrication of photonic crystals containing nonlinear optical materials is realized with high accuracy, a new ヽ -type phase matching can be realized, and the efficiency of various nonlinear optical operations can be improved compared to the conventional operating principle. It becomes possible to improve.
即ち、光の電場強度は群速度に反比例するので、フォトニック結晶に外部力 レー ザ一光を入射することにより、入射したレーザー光の数十倍以上の大変大きな光の 電場強度が実現できることになる。  In other words, since the electric field intensity of light is inversely proportional to the group velocity, a very large electric field intensity of several tens of times the incident laser light can be realized by making one external laser beam incident on the photonic crystal. Become.
ここで、非線形光学効果である第 2高調波発生について検討すると、第 2高調波発 生の場合には、高調波への変換効率は電場振幅の自乗に比例して増大するため、 本発明により上記した光の電場強度を増大するフォトニック結晶の作用を利用するこ とによって、第 2高調波発生について飛躍的な性能向上を図ることが期待できる。 さらに、波長変換素子においては、上記した光の電場強度の増大に加えて、入射 レーザー光 (基本波）と高調波との間の位相のマッチング (位相整合)をとることが重 要である力 フォトニック結晶では光の分散関係を自在に設計することができるため、 本発明によれば従来とは全く異なる手法で位相整合を達成することができる。このフ オトニック結晶による位相整合技術は、理想的な位相整合条件を満たすため、擬似 位相整合のような変換効率の低下は起こらな 、。 Here, when the second harmonic generation, which is a nonlinear optical effect, is studied, in the case of the second harmonic generation, the conversion efficiency to the harmonic increases in proportion to the square of the electric field amplitude. By using the action of the photonic crystal that increases the electric field intensity of light as described above, it is expected that the performance of the second harmonic generation will be dramatically improved. Furthermore, in the wavelength conversion element, in addition to the increase in the electric field intensity of the light described above, it is important to match the phase between the incident laser beam (fundamental wave) and the harmonic (phase matching). In the photonic crystal, the light dispersion relationship can be freely designed, and according to the present invention, phase matching can be achieved by a completely different method from the conventional one. This Since the phase matching technology using the tonic crystal satisfies the ideal phase matching condition, the conversion efficiency does not decrease like the pseudo phase matching.
従って、本発明によれば、位相整合と低群速度とを併せて実現することができ、非 線形光学特性を著しく向上することができる。  Therefore, according to the present invention, both phase matching and low group velocity can be realized, and the nonlinear optical characteristics can be remarkably improved.
[0006] 即ち、本発明は、上下のクラッド領域の間に、無機非線形光学結晶を含み、かつ、 周期的屈折率分布構造を与えるフォトニック結晶部を有するようにしたものである。  That is, according to the present invention, a photonic crystal part including an inorganic nonlinear optical crystal and providing a periodic refractive index distribution structure is provided between upper and lower cladding regions.
[0007] また、本発明は、上下にクラッド領域を有し、かつ、上記上下のクラッド領域の間に、 光を導波させる一層または複数層のコア層部を有し、かつ、上記上下のクラッド領域 または上記コア層部の少なくとも一部に、周期的屈折率分布構造を与えるフォトニッ ク結晶部を含み、かつ、上記上下のクラッド領域または上記コア層部の少なくとも一 部に無機非線形光学結晶を有するようにしたものである。  [0007] In addition, the present invention has a cladding region on the top and bottom, and has one or more core layer portions for guiding light between the top and bottom cladding regions, and the top and bottom At least a part of the cladding region or the core layer portion includes a photonic crystal portion that gives a periodic refractive index distribution structure, and an inorganic nonlinear optical crystal is formed on at least a part of the upper and lower cladding regions or the core layer portion. It is what you have.
[0008] また、本発明は、上下にクラッド領域を有し、かつ、上記上下のクラッド領域の間に、 光を導波させる一層または複数層のコア層部を有し、かつ、上記上下のクラッド領域 または上記コア層部の少なくとも一部に、 1次元または 2次元フォトニック結晶層を含 み、かつ、上記上下のクラッド領域または上記コア層部の少なくとも一部に無機非線 形光学結晶層を有するようにしたものである。  [0008] In addition, the present invention has a cladding region on the top and bottom, and has one or more core layer portions for guiding light between the top and bottom cladding regions, and the top and bottom At least a part of the cladding region or the core layer part includes a one-dimensional or two-dimensional photonic crystal layer, and an inorganic nonlinear optical crystal layer is formed on the upper and lower cladding regions or the core layer part. It is made to have.
[0009] また、本発明は、クラッド層と、上記クラッド層の上に形成された無機非線形光学結 晶層と、上記無機非線形光学結晶層の上に形成された 1次元または 2次元フォトニッ ク結晶層とを有するようにしたものである。  [0009] The present invention also provides a cladding layer, an inorganic nonlinear optical crystal layer formed on the cladding layer, and a one-dimensional or two-dimensional photonic crystal formed on the inorganic nonlinear optical crystal layer. And a layer.
[0010] また、本発明は、上記した発明において、上記無機非線形光学結晶層の厚さが、 光の波長レベルの厚さであるようにしたものである。  [0010] Further, the present invention is such that, in the above-described invention, the thickness of the inorganic nonlinear optical crystal layer is a thickness at a wavelength level of light.
[0011] また、本発明は、上記した発明において、上記無機非線形光学結晶層の厚さが、 5 Onm〜： LO μ mであるようにしたものである。  [0011] Further, in the present invention described above, the thickness of the inorganic nonlinear optical crystal layer is 5 Onm to LO μm.
[0012] また、本発明は、上記した発明において、上記無機非線形光学結晶層の厚さが、 2 OOnm〜l μ mであるようにしたものである。  [0012] The present invention is the above-described invention, wherein the inorganic nonlinear optical crystal layer has a thickness of 2 OOnm to lµm.
[0013] また、本発明は、上記した発明において、上記無機非線形光学結晶層は、無機非 線形光学結晶を表面研磨して薄膜形状に形成されたものである。  [0013] Further, according to the present invention, in the above-described invention, the inorganic nonlinear optical crystal layer is formed into a thin film shape by polishing the surface of the inorganic nonlinear optical crystal.
[0014] また、本発明は、上記した発明おいて、上記 1次元または 2次元フォトニック結晶層 は、 SiO系材料、ガラス系材料またはポリマー材料により形成されたものである。 [0014] Further, the present invention provides the above-described invention in which the one-dimensional or two-dimensional photonic crystal layer is Is formed of a SiO-based material, a glass-based material, or a polymer material.
2  2
[0015] また、本発明は、上記した発明において、上記無機非線形光学結晶層を構成する 無機非線形光学結晶は、 LiNbO結晶であるようにしたものである。  [0015] Further, according to the present invention, in the above-described invention, the inorganic nonlinear optical crystal constituting the inorganic nonlinear optical crystal layer is a LiNbO crystal.
3  Three
[0016] また、本発明は、非線形光学特性を有するフォトニック結晶の製造方法において、 クラッド層の上に無機非線形光学結晶層を形成する第 1の工程と、上記無機非線形 光学結晶層の上に 1次元または 2次元フォトニック結晶層を形成する第 2の工程とを 有するようにしたものである。  [0016] Further, the present invention provides a method for producing a photonic crystal having nonlinear optical characteristics, the first step of forming an inorganic nonlinear optical crystal layer on a cladding layer, and the inorganic nonlinear optical crystal layer on the inorganic nonlinear optical crystal layer. And a second step of forming a one-dimensional or two-dimensional photonic crystal layer.
[0017] また、本発明は、上記した発明において、上記第 1の工程は、上記無機非線形光 学結晶層の厚さを光の波長レベルの厚さに形成するようにしたものである。 [0017] Further, in the present invention described above, in the above-described invention, in the first step, the inorganic nonlinear optical crystal layer is formed to have a thickness at a wavelength level of light.
[0018] また、本発明は、上記した発明において、上記第 1の工程は、上記無機非線形光 学結晶層の厚さを 50nm〜10 mに形成するようにしたものである。 [0018] Further, according to the present invention, in the above-described invention, in the first step, the thickness of the inorganic nonlinear optical crystal layer is formed to be 50 nm to 10 m.
[0019] また、本発明は、上記した発明において、上記第 1の工程は、上記無機非線形光 学結晶層の厚さを 200ηπ！〜 1 μ mに形成するようにしたものである。 [0019] Further, in the present invention described above, in the first invention, in the first step, the thickness of the inorganic nonlinear optical crystal layer is set to 200ηπ! It is designed to form ~ 1 μm.
[0020] また、本発明は、上記した発明において、上記第 1の工程は、無機非線形光学結 晶を表面研磨して上記無機非線形光学結晶層を薄膜形状に形成するようにしたもの である。 [0020] Further, in the present invention described above, in the above-described invention, in the first step, the inorganic nonlinear optical crystal is surface-polished to form the inorganic nonlinear optical crystal layer in a thin film shape.
[0021] また、本発明は、上記した発明において、上記第 2の工程は、 SiO系材料、ガラス  [0021] Further, in the present invention according to the above-described invention, the second step includes: a SiO-based material, glass
2  2
系材料またはポリマー材料により上記 1次元または 2次元フォトニック結晶層を形成す るようにしたものである。  The one-dimensional or two-dimensional photonic crystal layer is formed of a system material or a polymer material.
[0022] また、本発明は、上記した発明において、上記第 2の工程は、 LiNbO結晶により [0022] Further, the present invention is the above invention, wherein the second step is performed by using a LiNbO crystal.
3 上記無機非線形光学結晶層を形成するようにしたものである。  3 The inorganic nonlinear optical crystal layer is formed.
[0023] また、本発明は、上記した発明において、上記第 2の工程は、上記無機非線形光 学結晶層の上に上記 1次元または 2次元フォトニック結晶層を形成するための材料を 配置し、ナノインプリントリソグラフィ一により上記材料に対して周期的構造を形成して 上記 1次元または 2次元フォトニック結晶層を形成するようにしたものである。 [0023] Further, in the present invention according to the above-described invention, in the second step, the material for forming the one-dimensional or two-dimensional photonic crystal layer is disposed on the inorganic nonlinear optical crystal layer. A one-dimensional or two-dimensional photonic crystal layer is formed by forming a periodic structure for the material by nanoimprint lithography.
発明の効果  The invention's effect
[0024] 本発明によれば、非線形光学特性に優れたフォトニック結晶およびその製造方法 を提供することができるという優れた効果が奏される。 図面の簡単な説明 [0024] According to the present invention, it is possible to provide an excellent effect that it is possible to provide a photonic crystal excellent in nonlinear optical characteristics and a method for manufacturing the photonic crystal. Brief Description of Drawings
[図 1]図 1 (a) (b) (c) (d) (e) (f) (g) (h) (i)は、本発明によるフォト ック結晶の製造 方法の処理手順を示す説明図である。 [FIG. 1] FIGS. 1 (a), (b), (c), (d), (e), (f), (g), (h), and (i) show the processing procedure of the photonic crystal manufacturing method according to the present invention. It is explanatory drawing.
[図 2]図 2は、非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶の概 念構成断面斜視説明図である。  [FIG. 2] FIG. 2 is a cross-sectional perspective view of a conceptual configuration of a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure.
[図 3]図 3は、図 1 (a)〜 (i)に示す製造方法で作製した非線形 2次元フォトニック結晶 導波路構造を備えたフォトニック結晶の断面の SEM (走査電子顕微鏡)写真の状態 を示す説明図である。  [Fig. 3] Fig. 3 is a SEM (scanning electron microscope) photograph of the cross section of a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i). It is explanatory drawing which shows a state.
[図 4]図 4は、図 1 (a)〜 (i)に示す製造方法で作製した非線形 2次元フォトニック結晶 導波路構造を備えたフォトニック結晶について求めた理論および実験によるフォト- ックバンド構造を示すグラフである。  [Fig. 4] Fig. 4 shows the photonic band structure obtained by the theory and experiment obtained for a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i). It is a graph which shows.
[図 5]図 5は、図 1 (a)〜 (i)に示す製造方法で作製した非線形 2次元フォトニック結晶 導波路構造を備えたフォトニック結晶について、基本波長 800nmの入射において、 CCDを用いる方式により得られた第 2高調波 (400nm)の発生を観測した結果と、フ オトニックバンドに共鳴する運動量 (入射角度）において第 2高調波の強度が大きく増 大した結果とを示すグラフである。  [Fig. 5] Fig. 5 shows a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i). A graph showing the results of observing the generation of the second harmonic (400 nm) obtained by the method used and the result of a significant increase in the intensity of the second harmonic at the momentum (incidence angle) resonating with the photonic band. It is.
[図 6]図 6は、図 1 (a)〜 (i)に示す製造方法で作製した非線形 2次元フォトニック結晶 導波路構造を備えたフォトニック結晶につ 、て、 650nmの基本励起 OPAレーザー の入射による第 2高調波（325nm)の発生を観測した結果を示すグラフである。  [Fig. 6] Fig. 6 shows a photonic crystal with a nonlinear two-dimensional photonic crystal waveguide structure fabricated by the manufacturing method shown in Figs. 1 (a) to (i). It is a graph which shows the result of having observed the generation | occurrence | production of the 2nd harmonic (325nm) by incidence | injection.
[図 7]図 7は、非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶によ り波長変換を行う際の構成例を示す説明図である。 FIG. 7 is an explanatory diagram showing a configuration example when wavelength conversion is performed using a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure.
[図 8]図 8 (a) (b) (c) (d) (e) (f) (g) (h) (i)は、本発明による 2次元フォト ック結晶層 の微細周期構造の作製にナノインプリントリソグラフィー技術を適用した場合の本発 明によるフォトニック結晶の製造方法の説明図である。  [Fig. 8] Fig. 8 (a) (b) (c) (d) (e) (f) (g) (h) (i) shows the fine periodic structure of the two-dimensional photonic crystal layer according to the present invention. FIG. 10 is an explanatory diagram of a photonic crystal manufacturing method according to the present invention when nanoimprint lithography technology is applied to the fabrication.
[図 9]図 9は、図 8 (a)〜 (i)に示す製造方法で作製した非線形 2次元フォトニック結晶 導波路構造を備えたフォトニック結晶の電子顕微鏡写真の状態を示す説明図である  [FIG. 9] FIG. 9 is an explanatory view showing the state of an electron micrograph of a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure manufactured by the manufacturing method shown in FIGS. 8 (a) to (i). is there
[図 10]図 10は、（a)〜 (i)に示す製造方法で作製した非線形 2次元フォトニック結晶 導波路構造を備えたフォトニック結晶の角度走査反射分光法による測定結果を示す グラフである。 [FIG. 10] FIG. 10 shows a nonlinear two-dimensional photonic crystal manufactured by the manufacturing method shown in (a) to (i). It is a graph which shows the measurement result by the angle scanning reflection spectroscopy of the photonic crystal provided with the waveguide structure.
符号の説明  Explanation of symbols
[0026] 10 フォトニック結晶  [0026] 10 Photonic crystal
12 LiNbO単結晶ウェハー  12 LiNbO single crystal wafer
12a  12a
12' LiNbO薄膜  12 'LiNbO thin film
3  Three
12' a 研磨面  12 'a polished surface
14 SiO膜  14 SiO film
16  16
16' LiNbO薄膜と SiO膜とよりなる基板  Substrate consisting of 16 'LiNbO thin film and SiO film
3 2  3 2
18 下地基板 18  18 Base substrate 18
20  20
22 PMMA  22 PMMA
24 ノヽードマスク材  24 Node mask material
26 レジスト材  26 Resist material
28 2次元フォトニック結晶層  28 Two-dimensional photonic crystal layer
100 フォトニック結晶  100 photonic crystals
114 Ag膜  114 Ag film
122 DR1/PMMA  122 DR1 / PMMA
128 2次元フォトニック結晶層  128 2D photonic crystal layer
130 Siモールド  130 Si mold
発明を実施するための最良の形態  BEST MODE FOR CARRYING OUT THE INVENTION
[0027] 以下、添付の図面を参照しながら、本発明によるフォトニック結晶およびその製造 方法の実施の形態の一例を詳細に説明するものとする。  [0027] Hereinafter, an example of an embodiment of a photonic crystal and a method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.
なお、以下の実施の形態においては、本発明によるフォトニック結晶として、最も代 表的な無機非線形光学結晶である LiNbO結晶を非線形光学材料として用いた 2次  In the following embodiments, as a photonic crystal according to the present invention, a LiNbO crystal, which is the most typical inorganic nonlinear optical crystal, is used as a nonlinear optical material.
3  Three
元フォトニック結晶構造を備えた導波路 (以下、「非線形 2次元フォトニック結晶導波 路」と適宜に称する。 )の構造を有するフォトニック結晶を作製する場合につ!ヽて説明 する。 Waveguide with original photonic crystal structure (hereinafter referred to as `` nonlinear two-dimensional photonic crystal waveguide '' It will be appropriately referred to as “road”. The case where a photonic crystal having the structure of) is produced will be described.
[0028] ここで、本願発明者は、高 、非線形光学特性をもつ材料を用いて非線形 2次元フォ トニック結晶導波路を作製する技術について、特開 2004— 133429号公報として既 に提案している。本発明は、この特開 2004— 133429号公報に開示された技術をさ らに発展させたものであるので、本発明の理解を容易にするために、まず、特開 200 4— 133429号公報に開示された技術の概要について説明する。  [0028] Here, the inventor of the present application has already proposed a technique for producing a nonlinear two-dimensional photonic crystal waveguide using a material having high nonlinear optical characteristics as Japanese Patent Application Laid-Open No. 2004-133429. . Since the present invention is a further development of the technique disclosed in Japanese Patent Application Laid-Open No. 2004-133429, in order to facilitate understanding of the present invention, first, Japanese Patent Application Laid-Open No. 2004-133429 An outline of the technique disclosed in the above will be described.
即ち、特開 2004— 133429号公報〖こは、主に非線形光学材料を用いた 2次元フォ トニック結晶導波路たる非線形 2次元フォトニック結晶導波路を実現するための素子 構造と作製方法とについて記載されている。より詳細には、特開 2004— 133429号 公報には、非線形光学材料として有機非線形光学ポリマーを用い、下部クラッド材料 として金属クラッド (具体的には銀である。）を用い、周期的構造よりなるフォトニック結 晶構造を備えた層（フォトニック結晶層）として透明なポリマー材料である PMMAを 用いて形成された 2次元フォトニック結晶層を備えた非線形 2次元フォトニック結晶導 波路の作製例と、作製された非線形 2次元フォトニック結晶導波路の第 2高調波発生 (SHG)特性と、作製された非線形 2次元フォトニック結晶導波路の光バンド構造特 性とが示されている。  In other words, JP-A-2004-133429 describes an element structure and a manufacturing method for realizing a nonlinear two-dimensional photonic crystal waveguide that is a two-dimensional photonic crystal waveguide mainly using a nonlinear optical material. Has been. More specifically, in Japanese Patent Application Laid-Open No. 2004-133429, an organic nonlinear optical polymer is used as a nonlinear optical material, a metal cladding (specifically, silver) is used as a lower cladding material, and a periodic structure is used. Examples of fabrication of nonlinear two-dimensional photonic crystal waveguides with two-dimensional photonic crystal layers formed using PMMA, which is a transparent polymer material, as layers with photonic crystal structures (photonic crystal layers) The second harmonic generation (SHG) characteristics of the fabricated nonlinear 2D photonic crystal waveguide and the optical band structure characteristics of the fabricated nonlinear 2D photonic crystal waveguide are shown.
[0029] 以下、図 1 (a)〜(i)を参照しながら、本発明によるフォトニック結晶の製造方法につ いて説明すると、まず、 0. 5〜lmm程度の LiNbO単結晶ウェハー（この実施の形  Hereinafter, the method for producing a photonic crystal according to the present invention will be described with reference to FIGS. 1 (a) to (i). First, a LiNbO single crystal wafer of about 0.5 to 1 mm (this implementation) Form of
3  Three
態においては、 MgO :LiNbOの 3インチウェハーを用いた。） 12に対し（図 1 (a)参  In this state, a 3-inch wafer of MgO: LiNbO was used. ) 12 (see Fig. 1 (a))
3  Three
照）、クラッド層として利用する SiO膜 14をプラズマ CVD法により 4 /z m程度の厚さで  The SiO film 14 used as a cladding layer is about 4 / zm thick by plasma CVD.
2  2
成膜した基板 16を作製する（図 1 (b)参照)。  A film-formed substrate 16 is produced (see FIG. 1 (b)).
次に、その基板 16の SiO膜 14と下地基板 18として用いる Siウェハーとを接着剤（  Next, the SiO film 14 of the substrate 16 and the Si wafer used as the base substrate 18 are bonded with an adhesive (
2  2
具体的には、例えば、アクリル系ポリマーなどである。）により貼り合わせ（図 1 (c)参 照）、ァニールする（図 1 (d)参照)。なお、この際に、接着剤層 20の厚さが、 0. 3〜0 . 5 /z m程度となるようにする。  Specifically, for example, an acrylic polymer is used. ) (See Fig. 1 (c)) and anneal (see Fig. 1 (d)). At this time, the thickness of the adhesive layer 20 is set to about 0.3 to 0.5 / zm.
次に、 LiNbO単結晶ウェハー 12の厚さが光の波長レベルの厚さ、例えば、 50nm  Next, the thickness of the LiNbO single crystal wafer 12 is the thickness of the wavelength level of light, for example, 50 nm
3  Three
〜 10 /z m程度の厚さとなるまで、基板 16に形成された SiO膜 14側の反対側の面、 即ち、 LiNbO単結晶ウェハー 12の表面 12aを研磨機により研磨する（図 1 (e)参照The surface on the opposite side of the SiO film 14 side formed on the substrate 16 until a thickness of about 10 / zm, That is, the surface 12a of the LiNbO single crystal wafer 12 is polished by a polishing machine (see FIG. 1 (e)).
3 Three
)。なお、 LiNbO単結晶ウェハー 12の研磨により形成された無機非線形光学結晶  ). Inorganic nonlinear optical crystal formed by polishing LiNbO single crystal wafer 12
3  Three
層たる LiNbO薄膜を符号 12 'で示し、 LiNbO薄膜 12 'と SiO膜 14とよりなる基板 A substrate made of LiNbO thin film 12 'and SiO film 14 is indicated by reference numeral 12'.
3 3 2  3 3 2
を符号 16 'で示すこととする。 Is denoted by 16 '.
ここで、上記した研磨機による研磨工程は、以下の工程 1〜4に示す手順に従って 行われる。  Here, the polishing process by the polishing machine described above is performed according to the procedure shown in the following processes 1 to 4.
工程 1：固定砥粒による研削  Process 1: Grinding with fixed abrasive
0. 5〜： Lmm程度の厚さの LiNbO単結晶ウェハー 12を 0. 05mm程度の厚  0.5 ~: LiNbO single crystal wafer 12 with a thickness of about Lmm is about 0.05mm thick
3  Three
さになるまで研磨する。この工程 1は、横型研削機により行われる。 Polish until it is. This step 1 is performed by a horizontal grinding machine.
工程 2：ダイヤモンドスラリ一〖こよる粗研磨  Process 2: Rough polishing with a diamond slurry
LiNbO単結晶ウェハー 12の厚さを 50 μ m力ら 5 μ m程度まで研磨する。こ Polish the thickness of the LiNbO single crystal wafer 12 from 50 μm force to about 5 μm. This
3 Three
の工程 2は、高速ラップ研磨機により行われる。 Step 2 is performed by a high speed lapping machine.
工程 3 :ダイヤモンドスラリーによる精密研磨  Process 3: Precision polishing with diamond slurry
LiNbO単結晶ウェハー 12の厚さを 5 mから 2. 0 m程度まで研磨する。  Polish the thickness of LiNbO single crystal wafer 12 from 5 m to 2.0 m.
3  Three
この工程 3は、高速ラップ研磨機により行われる。 This step 3 is performed by a high speed lapping machine.
工程 4 : SiOスラリーによる仕上げ研磨  Process 4: Finish polishing with SiO slurry
2  2
LiNbO単結晶ウェハー 12の厚さが波長レベルの厚さとなるように、 2. 0 μ 2.0 μm so that the thickness of LiNbO single crystal wafer 12 is the thickness of the wavelength level
3 Three
mから 0. 5 m程度までの適宜の厚さに研磨して、無機非線形光学結晶層たる LiN bO薄膜 12，を得る。この工程 4は、オスカー研磨機により行われる。 By polishing to an appropriate thickness from m to about 0.5 m, a LiN bO thin film 12, which is an inorganic nonlinear optical crystal layer, is obtained. This step 4 is performed by an Oscar polisher.
3  Three
次に、上記のようにして LiNbO単結晶ウェハー 12を研磨して形成した LiNbO薄  Next, the LiNbO thin film formed by polishing the LiNbO single crystal wafer 12 as described above.
3 3 膜 12 'の研磨面 12 ' a上に、電子線リソグラフィーおよび反応性ガスを用いた ICPドラ ィエッチングにより高垂直性かつ高アスペクト比を持つ周期的構造よりなる 2次元フォ トニック結晶構造を作製して、 2次元フォトニック結晶層 28 (図 1 (i)参照）を形成する。 具体的には、 2次元フォトニック結晶層 28を形成するための PMMA22を 300nm 〜1 /ζ πι程度の厚さにスピンコートして 100〜180°C程度でベイクし、次に、ドライエツ チング用のハードマスク材 24として SOG (SiO系塗布材）を 100  3 3 A two-dimensional photonic crystal structure consisting of a periodic structure with high perpendicularity and high aspect ratio is formed on the polished surface 12'a of film 12 'by electron beam lithography and ICP dry etching using reactive gas. The two-dimensional photonic crystal layer 28 (see FIG. 1 (i)) is formed. Specifically, PMMA22 for forming the two-dimensional photonic crystal layer 28 is spin-coated to a thickness of about 300 nm to 1 / ζ πι, baked at about 100 to 180 ° C, and then for dry etching. SOG (SiO coating material) 100 as hard mask material 24
2 〜200nm程度の 厚さにスピンコートして 100〜180°C程度でベイクし、次に、電子ビーム露光用のレジ スト材（ここでは ZEP520) 26を 100〜500nm程度の厚さにスピンコートして 100〜1 80°C程度でベイクして積層する（図 1 (f )参照)。 Spin coat to a thickness of about 2 to 200 nm, bake at about 100 to 180 ° C, and then spin coat the resist material for electron beam exposure (here ZEP520) 26 to a thickness of about 100 to 500 nm. 100-1 Bake and stack at about 80 ° C (see Fig. 1 (f)).
それから、電子ビーム露光装置を用いた電子線リソグラフィ一により、所望の周期的 構造よりなる 2次元周期ノターンを描画する（図 1 (g)参照)。なお、この実施の形態 に!、ては、直径 200nm程度のホールパターンを周期 500nm程度の正方格子状に パターニングした。  Then, a two-dimensional periodic pattern consisting of the desired periodic structure is drawn by electron beam lithography using an electron beam exposure system (see Fig. 1 (g)). In this embodiment, a hole pattern with a diameter of about 200 nm was patterned into a square lattice with a period of about 500 nm.
次に、フッ素系反応ガスを用いたドライエッチングによりハードマスク材 24にパター ン転写し、ついで O ZAr反応ガスを用いたドライエッチングにより、 PMMA22に対  Next, the pattern was transferred to the hard mask material 24 by dry etching using a fluorine-based reactive gas, and then applied to PMMA 22 by dry etching using an O ZAr reactive gas.
2  2
して高精度にフォトニック結晶構造の加工を行う（図 1 (h)参照)。 Then, the photonic crystal structure is processed with high accuracy (see Fig. 1 (h)).
最後にハードマスク 24の除去を行うことにより、波長変換部である無機非線形光学 結晶層たる LiNbO薄膜 12'と、 2次元フォトニック結晶構造よりなるフォトニック結晶  Finally, by removing the hard mask 24, an inorganic nonlinear optical crystal layer, the LiNbO thin film 12 ', which is the wavelength conversion section, and a photonic crystal consisting of a two-dimensional photonic crystal structure
3  Three
部である周期的屈折率変調層たる 2次元フォトニック結晶層 28とが互いに分離して 形成されているとともに、両者を一体的に結合して構成した 2層コア構造を有する非 線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶 10を作製することが できた (図 l (i)参照)。 The two-dimensional photonic crystal layer 28, which is a periodic refractive index modulation layer, is formed separately from each other and has a two-layer core structure formed by integrally coupling the two layers. A photonic crystal 10 with a nick crystal waveguide structure could be fabricated (see Fig. L (i)).
図 2には、上記のようにして作製されたフォトニック結晶周期 500nmであり正方格子 構造を持つ非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶 10の 概念構成断面斜視説明図が示されている。  Fig. 2 shows a cross-sectional perspective view of the conceptual configuration of a photonic crystal 10 having a nonlinear two-dimensional photonic crystal waveguide structure with a square lattice structure and a photonic crystal period of 500 nm fabricated as described above. Has been.
また、図 3には、上記のようにして作製されたフォトニック結晶周期 500nmであり正 方格子構造を持つ非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結 晶 10の断面の SEM (走査電子顕微鏡)写真の状態を示す説明図が示されている。 この実施の形態によるフォトニック結晶 10においては、接着剤層 20の膜厚は約 30 Onmであり、 SiO膜の膜厚は約 4 mであり、 LiNbO薄膜 12，の膜厚は約 60nmで  In addition, Fig. 3 shows a cross-sectional SEM of a photonic crystal 10 with a nonlinear two-dimensional photonic crystal waveguide structure with a photonic crystal period of 500 nm and a square lattice structure fabricated as described above ( Scanning electron microscope) An explanatory view showing the state of a photograph is shown. In the photonic crystal 10 according to this embodiment, the thickness of the adhesive layer 20 is about 30 Onm, the thickness of the SiO film is about 4 m, and the thickness of the LiNbO thin film 12 is about 60 nm.
2 3  twenty three
あり、 2次元フォトニック結晶層 28の膜厚は約 900nmである。 The film thickness of the two-dimensional photonic crystal layer 28 is about 900 nm.
上記した本発明よるフォトニック結晶の製造方法によれば、難加工性材料である Li NbO単結晶を使用して非線形 2次元フォトニック結晶導波路構造を備えたフォト-ッ According to the photonic crystal manufacturing method of the present invention described above, a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure using a Li NbO single crystal, which is a difficult-to-work material, is used.
3 Three
ク結晶を作製することができるものであり、非線形光学特性やその動作特性が良好で はあるが加工性に劣るため、従来はフォトニック結晶に利用することが困難であった L iNbO単結晶などの無機非線形光学結晶を、フォトニック結晶として利用することが でさるよう〖こなる。 LiNbO single crystals, etc. that were difficult to use for photonic crystals in the past because of their non-linear optical characteristics and their operational characteristics but poor workability. Inorganic nonlinear optical crystals can be used as photonic crystals It ’s a little tricky.
なお、以下に説明するように、本発明よるフォトニック結晶の製造方法により作製さ れた非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶は、従来の 技術に比べて第 2高調波発生の著 U、増強を実証し、波長変換素子として極めて有 効性であることが示された。  As will be described below, a photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure manufactured by a photonic crystal manufacturing method according to the present invention has a second harmonic compared to the conventional technology. It was demonstrated that the generation of U and enhancement was extremely effective as a wavelength conversion element.
ここで、素子動作の設計および評価を正確に行うためには、作製された非線形 2次 元フォトニック結晶導波路構造を備えたフォトニック結晶 10が、どのようなバンド構造 を持つものであるのかを理論的にシミュレーションすると同時に、実験的に直接観測 することが必要となる。  Here, in order to accurately design and evaluate the device operation, what kind of band structure is the photonic crystal 10 with a nonlinear two-dimensional photonic crystal waveguide structure manufactured? In addition to theoretical simulation, it is necessary to observe directly experimentally.
フォトニック結晶 10に関する理論計算に関しては、平面波展開法に比べてより精度 の高 、、 3次元 FDTD法によるバンド計算法を用いて解析を行った。  The theoretical calculation for the photonic crystal 10 was analyzed using a band calculation method based on the three-dimensional FDTD method, which is more accurate than the plane wave expansion method.
また、実験的には、角度走査偏光反射率測定を行い、反射スペクトルにおいて鋭 Vヽ極小として現れる共鳴ピーク位置力 フォトニックバンド構造を決定した。具体的に は、タングステンハロゲン白色光源を用いた各偏光平行ビームを、微小なサンプル（ ノターニング)部に対して集光入射し、分光器および CCDを用いて反射スペクトルを 測定し、さらにビーム入射角および結晶対称軸に対する面内ビーム進行角をそれぞ れ走査し、スペクトルに現れる共鳴ピークの周波数シフトからフォトニックバンド分散 曲線を追跡した。  Experimentally, the angle scanning polarization reflectance measurement was performed, and the resonance peak position force photonic band structure that appears as a sharp V-minimum in the reflection spectrum was determined. Specifically, each polarized parallel beam using a tungsten halogen white light source is focused on a small sample (not turning) part, and the reflection spectrum is measured using a spectroscope and a CCD. The in-plane beam advance angle with respect to the angle and the crystal symmetry axis was scanned, and the photonic band dispersion curve was traced from the frequency shift of the resonance peak appearing in the spectrum.
上記したように理論および実験の両面力 バンド構造を決定すれば、超低群速度 ならびに位相整合を同時に満たし、波長変換効率が著しく増大される動作条件を正 確に求め、かつ、素子性能を評価することができる。  If the band structure of both theory and experiment is determined as described above, the operating conditions under which the ultra-low group velocity and phase matching are simultaneously satisfied, and the wavelength conversion efficiency is remarkably increased, and the device performance is evaluated. can do.
図 4には、上記のようにして作製されたフォトニック結晶周期 500nmであり正方格子 構造を持つ非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶 10に ついて、上記したようにして求めた理論および実験によるフォトニックバンド構造が示 されている。  Figure 4 shows the photonic crystal 10 with a nonlinear two-dimensional photonic crystal waveguide structure with a square lattice structure and a photonic crystal period of 500 nm fabricated as described above. Theoretical and experimental photonic band structures are shown.
この図 4から明らかなように、実験によるフォトニックバンドと理論によるフォト-ックバ ンドとは非常に良く一致しており、上記したフォトニック結晶 10が精度よく作製された ことが示されている。後述するように、上記したフォトニック結晶 10において、光バンド に共鳴する条件で従来より 300倍以上の大きな SHG強度増大が観測された。 As is clear from FIG. 4, the experimental photonic band and the theoretical photonic band are in good agreement, indicating that the photonic crystal 10 described above was fabricated with high accuracy. As will be described later, in the photonic crystal 10 described above, the optical band A large SHG intensity increase of more than 300 times was observed under the condition of resonating with.
なお、フォトニック結晶周期を変化すれば、図 4の縦軸に示す光子エネルギーは自 由に変更することができる。  If the photonic crystal period is changed, the photon energy shown on the vertical axis in FIG. 4 can be freely changed.
次に、上記したフォトニック結晶 10を用いて、実際に第 2高調波発生過程の評価を行 つた実験について説明する。 Next, an experiment in which the second harmonic generation process was actually evaluated using the photonic crystal 10 described above will be described.
第 2高調波発生測定の際に入射光の波長および入射角度ならびにフォトニック結 晶に対するビーム進行角度を走査することによって、フォトニックバンドの位置に共鳴 するエネルギーおよび運動量において、出力される第 2高調波の強度が増大するこ とにより、バンドの位置の同定およびその強度の増大の度合いから、光バンドと関連 した増大の定量的調査、確認および最も効率良くフォトニック結晶が動作する条件の 調査、確認を行うことができる。  By scanning the wavelength and angle of incident light and the beam traveling angle relative to the photonic crystal during the second harmonic generation measurement, the second harmonic output at the energy and momentum that resonates with the position of the photonic band. By increasing the intensity of the wave, we can quantitatively investigate and confirm the increase associated with the optical band from the identification of the position of the band and the extent of its intensity, and the conditions under which the photonic crystal operates most efficiently, Confirmation can be made.
本実施の形態における実験では、入射光源として広範囲にわたり波長可変可能 (0 . 3〜： LO m)な短パルス OPA (短パルス光パラメトリック増幅器)を用いた。入射光 学系は、上記した角度走査偏光反射率測定のものと同様のものを用いた。なお、励 起光の高調波成分は、試料入射直前に干渉フィルタ一により取り除いた。また、高調 波の検知部は、ファイバーによって分光器や CCDに取り込む力、またはバンドパスフ ィルターを通して光電子増倍管に取り込む形式を用いればょ 、が、この実験にぉ ヽ ては CCDを用いた。  In the experiment in the present embodiment, a short pulse OPA (short pulse optical parametric amplifier) capable of changing the wavelength over a wide range (0.3 to LO m) was used as the incident light source. The incident optical system was the same as that used for the above-mentioned angle scanning polarization reflectance measurement. The harmonic component of the excitation light was removed by an interference filter just before the sample was incident. In addition, the harmonic detector used a force to be taken into the spectroscope and CCD by a fiber, or a form to be taken into a photomultiplier tube through a bandpass filter, but for this experiment, a CCD was used.
図 5には、基本波長 800nmの入射において、 CCDを用いる方式により得られた第 2高調波 (400nm)の発生を観測した結果と、フォトニックバンドに共鳴する運動量（ 入射角度）において第 2高調波の強度が大きく増大した結果とが示されている。即ち 、光バンドに共鳴する運動量において、バルタ部に対して 300倍以上の強度増大を 観測した。  Figure 5 shows the results of observing the generation of the second harmonic (400 nm) obtained by the CCD method at an incident wavelength of 800 nm and the second harmonic in the momentum (incident angle) resonating with the photonic band. The result shows that the wave intensity is greatly increased. In other words, in the momentum resonating with the optical band, an intensity increase of 300 times or more with respect to the Balta part was observed.
また、図 6には、他の実験結果として、上記したフォトニック結晶 10に 650nmの基 本励起 OPAレーザーを入射した結果が示されて 、る。この図 6の実験結果に示され ているように、フォトニック結晶 10に 650nmの基本励起 OPAレーザーを入射したとこ ろ、強 、第 2高調波 (波長 325nm)の発生が観測された。  In addition, FIG. 6 shows the result of the incident of a 650 nm basic excitation OPA laser on the photonic crystal 10 as another experimental result. As shown in the experimental results of FIG. 6, when a 650 nm basic excitation OPA laser was incident on the photonic crystal 10, the generation of strong second harmonics (wavelength 325 nm) was observed.
従って、上記したフォトニック結晶 10によれば、通常媒質中に比べてはるかに高効 率で高調波を実際に発生できるものである。 Therefore, according to the photonic crystal 10 described above, it is much more effective than in a normal medium. It is possible to actually generate harmonics at a rate.
なお、上記した実験においては、外部力 基本レーザー光を入射して、反射 SHG を測定するようにした力 例えば、図 7に示すように、光学系レンズや、あるいは、光 学系レンズ、導波路、プリズム、グレーティング、光ファイバ一、レーザー素子などの 直接接合あるいはそれらの組み合わせを通して基本レーザー光 (基本波）を非線形 2次元フォトニック結晶導波路構造の面内に導波させてやれば、より長い相互作用長 が得られることになり、また非常に微小な領域に光を閉じ込めことができるため、より 高 、効率で波長変換を行うことができるようになる。このとき位相整合条件をフォト-ッ クバンド構造により満たしてやれば、距離の 2乗に比例して SHG強度は増加し、また 、同時に低群速度バンドの電場増強効果により極めて強い変換効率の増大が得られ るよつになる。  In the experiment described above, the external force is a force that makes basic laser light incident and measures the reflected SHG. For example, as shown in FIG. 7, an optical lens, optical lens, or waveguide is used. It is longer if the fundamental laser light (fundamental wave) is guided in the plane of the nonlinear two-dimensional photonic crystal waveguide structure through direct bonding of a prism, grating, optical fiber, laser element, or a combination thereof. An interaction length can be obtained, and light can be confined in a very small region, so that wavelength conversion can be performed with higher efficiency. At this time, if the phase matching condition is satisfied by the photo-band structure, the SHG intensity increases in proportion to the square of the distance, and at the same time, an extremely strong increase in conversion efficiency is obtained due to the electric field enhancement effect of the low group velocity band. You will be able to be.
以上において説明したように、本発明によれば、代表的な非線形光学結晶である L iNbO結晶を用いて、非線形 2次元フォトニック結晶導波路構造を備えたフォトニック As described above, according to the present invention, a photonic having a nonlinear two-dimensional photonic crystal waveguide structure using a LiNbO crystal, which is a typical nonlinear optical crystal, is used.
3 Three
結晶 10を作製することができた。フォトニック結晶 10は、クラッド層として SiO膜 14を Crystal 10 could be made. The photonic crystal 10 has a SiO film 14 as a cladding layer.
2 予め成膜した LiNbO結晶ウェハー 12を研磨過程を通して薄膜ィ匕し、その上に 2次  2 Pre-deposited LiNbO crystal wafer 12 is thinned through the polishing process, and then the secondary
3  Three
元フォトニック結晶層 28を微細加工技術を用いて作製したものである。さらに、。フォ トニック結晶 10に対し、外部からレーザー光を入射し、第 2高調波発生 (SHG)を観 測し、またフォトニック結晶 10の効果による SHG強度の増大を観測した。 The original photonic crystal layer 28 is produced using a fine processing technique. further,. Laser light was incident on the photonic crystal 10 from the outside, second harmonic generation (SHG) was observed, and an increase in SHG intensity due to the effect of the photonic crystal 10 was observed.
これまでは、 LiNbO  Until now, LiNbO
3結晶に代表される無機非線形光学結晶は、高い非線形光学 性能とデバイス動作安定性を持ちながら、半導体材料や有機材料などに比べ、微細 加工プロセスに対する加工性が悪いために、フォトニック結晶への応用が困難であつ た。  Inorganic nonlinear optical crystals represented by three crystals have high nonlinear optical performance and device operation stability, but are less workable for microfabrication processes than semiconductor materials and organic materials. Application was difficult.
しカゝしながら、本発明によれば、非線形光学材料として用いる無機非線形光学結晶 そのものは、微細な孔を空けるなどの加工を必要とせずに単に薄膜ィ匕するだけでよく 、これにより非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶を作 製することができるものであり、従って、難加工材料である無機非線形光学結晶を用 いながら高精度なフォトニック結晶を実現することが可能となる。  However, according to the present invention, the inorganic nonlinear optical crystal itself used as the nonlinear optical material can be simply formed into a thin film without requiring processing such as making fine holes. Photonic crystals with a three-dimensional photonic crystal waveguide structure can be manufactured. Therefore, it is possible to realize highly accurate photonic crystals using inorganic nonlinear optical crystals, which are difficult to process materials. It becomes possible.
即ち、本発明によるフォトニック結晶の製造方法は、無機非線形光学結晶が微細加 ェプロセスに対する加工性が悪いという欠点を解消するものである。また、無機非線 形光学結晶に微細周期構造用の微細加工をしないで済むため、 2次元フォトニック 結晶層 28に加工性の高い材料を選択すれば、非常に高精度な加工レベルのフォト ニック結晶を作製することが可能になる。これにより、無駄な光散乱や光損失を避け、 また、誤差や加工揺らぎの少な ヽ理論設計に近 ヽデバイスが得られるようになるため 、結果として非常に高効率な波長変換効率が得られることになる。 That is, the method for producing a photonic crystal according to the present invention adds fine inorganic nonlinear optical crystals. This eliminates the disadvantage of poor processability for the process. In addition, since the inorganic nonlinear optical crystal does not need to be finely processed for a fine periodic structure, if a highly workable material is selected for the two-dimensional photonic crystal layer 28, photonics with a very high processing level can be obtained. Crystals can be produced. This avoids useless light scattering and light loss, and also enables devices that are close to theoretical design with less error and processing fluctuations, resulting in extremely high wavelength conversion efficiency. become.
また、無機非線形光学結晶に微細周期構造用の微細加工をしないで済むことは、 2次元フォトニック結晶層 28の材料として任意のものを用いることができるものであり、 また、どのようなカ卩工法を用いてもよいということを意味する。この特徴により、加工精 度を最大限に上げることができるということは勿論であるが、 2次元フォトニック結晶層 28に透明な有機材料やガラス材料のようなものを用いれば、微細周期構造の作製に ナノインプリントリソグラフィー技術を適用することが可能となり。これによりフォトニック 結晶の製造コストを著しく低減することができるようになる。  In addition, the fact that the inorganic nonlinear optical crystal does not have to be finely processed for a fine periodic structure is that any material can be used as the material of the two-dimensional photonic crystal layer 28. It means that the construction method may be used. Of course, this feature allows the processing accuracy to be maximized. However, if a transparent organic material or glass material is used for the two-dimensional photonic crystal layer 28, a fine periodic structure can be obtained. It becomes possible to apply nanoimprint lithography technology to the production. As a result, the manufacturing cost of the photonic crystal can be significantly reduced.
図 8 (a)〜 (i)は、 2次元フォトニック結晶層の微細周期構造の作製にナノインプリン トリソグラフィー技術を適用した場合の本発明によるフォトニック結晶の製造方法の説 明図である。なお、この図 8 (a) (b) (c) (d) (e)は、クラッド層とし SiO膜 14の代わりに  FIGS. 8 (a) to (i) are explanatory diagrams of a method for producing a photonic crystal according to the present invention when nanoimprint lithography technology is applied to the production of a fine periodic structure of a two-dimensional photonic crystal layer. . 8 (a), (b), (c), (d), and (e) are used as cladding layers instead of the SiO film 14.
2  2
Ag膜 114を用いている点を除いて、図 1 (a) (b) (c) (d) (e)とそれぞれ同一の処理を 示すものであるので、その詳細な説明は省略する。  Except that the Ag film 114 is used, the same processing as in FIGS. 1 (a), (b), (c), (d), and (e) is shown, and a detailed description thereof is omitted.
この図 8に示す本発明によるフォトニック結晶の製造方法においては、図 8 (e)に示 す処理を終了すると、 LiNbO単結晶ウェハー 12を研磨して形成した LiNbO薄膜 1  In the method for producing a photonic crystal according to the present invention shown in FIG. 8, when the process shown in FIG. 8 (e) is completed, a LiNbO thin film 1 formed by polishing a LiNbO single crystal wafer 12 1.
3 3 3 3
2'の研磨面 12' a上に、ナノインプリントリソグラフィー技術により高垂直性かつ高ァス ぺクト比を持つ周期的構造たる 2次元フォトニック結晶構造を作製して、 2次元フォト ニック結晶層 128 (図 8 (i)参照）を形成する。 A two-dimensional photonic crystal layer 128 (a periodic structure with a high perpendicularity and a high aspect ratio) is fabricated on the 2 'polished surface 12' a using nanoimprint lithography technology. (See Fig. 8 (i)).
具体的には、 2次元フォトニック結晶層 128を形成するための DR1ZPMMA122 を 300nm〜l μ m程度の厚さにスピンコートして積層する（図 8 (f)参照）。  Specifically, DR1ZPMMA122 for forming the two-dimensional photonic crystal layer 128 is spin-coated to a thickness of about 300 nm to l μm and stacked (see FIG. 8 (f)).
次に、所望のパターンを形成された Siモールド 130の表面に剥離剤（シラン系単分 子膜)をコートする。  Next, a release agent (silane-based monomolecular film) is coated on the surface of the Si mold 130 on which a desired pattern is formed.
それから、 Siモールド 130を DR1ZPMMA122上に載置して、加熱しながら加圧 する（図 8 (g)参照)。なお、この実施の形態においては、直径 200nm程度のホール ノターンを周期 600nmの正方格子状にパターユングした周期的構造を備えた Siモ 一ルド 130を用いた。また、加熱する際の温度は、ガラス転位温度 Tg前後の温度（5 0〜200°C)とし、この温度条件において Siモールド 130に形成されたパターンを DR 1ZPMMA122に直接転写した。 Then, place Si mold 130 on DR1ZPMMA122 and pressurize while heating (See Fig. 8 (g)). In this embodiment, Si mold 130 having a periodic structure in which a hole pattern having a diameter of about 200 nm is patterned into a square lattice having a period of 600 nm is used. The temperature at the time of heating was set to a temperature (50 to 200 ° C.) around the glass transition temperature Tg, and the pattern formed on the Si mold 130 was directly transferred to the DR 1ZPMMA 122 under this temperature condition.
次に、 Siモールド 130の冷却を行ってから、 PMMA122力ら Siモールド 130を引き 剥がすと（図 8 (h)参照）、波長変換部である非線形光学材料層たる LiNbO薄膜 12  Next, after cooling the Si mold 130 and peeling the Si mold 130 with PMMA 122 force (see Fig. 8 (h)), the LiNbO thin film as the nonlinear optical material layer that is the wavelength conversion section 12
3 Three
'と、 2次元フォトニック結晶構造よりなるフォトニック結晶部である周期的屈折率変調 層たる 2次元フォトニック結晶層 128とが互いに分離して形成されて 、るとともに、両 者を一体的に結合して構成した 2層コア構造を有する非線形 2次元フォトニック結晶 導波路構造を備えたフォトニック結晶 100を作製することができた (図 8 (i)参照)。 図 9には、上記のようにして作製した非線形 2次元フォトニック結晶導波路構造を備 えたフォトニック結晶 100の電子顕微鏡写真の状態を示す説明図が示されており、ま た、図 10には、角度走査反射分光法による測定結果を示すグラフが示されている。 これら図 9に示す電子顕微鏡写真の状態を示す説明図や図 10のグラフが示す明 確に観測された光バンド共鳴ディップにより、素子の高精度加工が実証された。 この 2次元フォトニック結晶層の微細周期構造の作製にナノインプリントリソグラフィ 一技術を適用した本発明によるフォトニック結晶の製造方法によれば、フォトニック結 晶を画期的な低コストで作製することが可能になり、し力も高精度で大面積かつ大量 かつ高スループットな生産性を実現性することが可能になる。 And the two-dimensional photonic crystal layer 128, which is a periodic refractive index modulation layer, which is a photonic crystal portion having a two-dimensional photonic crystal structure, are formed separately from each other, and the two are integrated with each other. A photonic crystal 100 having a nonlinear two-dimensional photonic crystal waveguide structure with a two-layer core structure formed by coupling was successfully fabricated (see Fig. 8 (i)). FIG. 9 is an explanatory diagram showing the state of an electron micrograph of the photonic crystal 100 having a nonlinear two-dimensional photonic crystal waveguide structure fabricated as described above, and FIG. Shows a graph showing the measurement results by angle scanning reflection spectroscopy. High-precision processing of the device was demonstrated by the optical band resonance dip observed clearly in the explanatory diagram showing the state of the electron micrograph shown in FIG. 9 and the graph of FIG. According to the photonic crystal manufacturing method according to the present invention, in which a technique of nanoimprint lithography is applied to the production of the fine periodic structure of the two-dimensional photonic crystal layer, the photonic crystal can be produced at an epoch-making low cost. This makes it possible to achieve high-precision, large-area, large-volume, high-throughput productivity.
なお、本発明によれば、上記したように、従来の手法では不可能な電場の増強と位 相整合とを同時に満たすことが可能であり、また、形成した 2次元フォトニック結晶導 波路構造は、導波路であるため光を非常に微小な領域に閉じ込めることによって非 常に強い光強度で最も長い相互作用長を取れることから、波長変換過程の特性上に ぉ 、て他の構造より断然有利である。  In addition, according to the present invention, as described above, it is possible to simultaneously satisfy the electric field enhancement and the phase matching which are impossible with the conventional method, and the formed two-dimensional photonic crystal waveguide structure is Because it is a waveguide, the longest interaction length can be obtained with very strong light intensity by confining the light in a very small area, which is far more advantageous than other structures in terms of the characteristics of the wavelength conversion process. is there.
また、本発明によれば、クラッド層も基本波と高調波とに対して吸収の無い透明材 料で作ることが可能であるので、長い相互作用長を取ってもまったく吸収の問題が無 い。 なお、上記した実施の形態は、以下の（1)乃至（13)に示すように変形することがで きるものである。 Further, according to the present invention, the cladding layer can also be made of a transparent material that does not absorb fundamental waves and harmonics, so there is no problem of absorption even if a long interaction length is taken. . The embodiment described above can be modified as shown in the following (1) to (13).
(1)上記した実施の形態においては、本発明によるフォトニック結晶として、非線形 2次元フォトニック結晶導波路構造を備えたフォトニック結晶について説明した力 こ れに限られるものではなぐ適宜の構造を備えるようにしてもよいことは勿論である。ま た、フォトニック結晶構造も 2次元に限られるものではなぐ各種のフォトニック結晶構 造を備えてよいことは勿論である。さらに、無機非線形光学結晶は、層状に形成され ていなくてもよい。  (1) In the embodiment described above, the structure described in the photonic crystal having a nonlinear two-dimensional photonic crystal waveguide structure as the photonic crystal according to the present invention is not limited to this, and an appropriate structure is used. Of course, it may be provided. Of course, the photonic crystal structure is not limited to two dimensions, and various photonic crystal structures may be provided. Furthermore, the inorganic nonlinear optical crystal may not be formed in a layered form.
(2)上記した実施の形態においては、無機非線形光学結晶として LiNbO結晶を  (2) In the above embodiment, LiNbO crystal is used as the inorganic nonlinear optical crystal.
3 用いたが、これに限られるものではないことは勿論であり、無機非線形光学結晶とし ては、例えば、 LiTaO (LT)、 KH PO (KDP)、 KTiOPO (KTP) , BaB O (BB  3 Of course, this is not a limitation, but examples of inorganic nonlinear optical crystals include LiTaO (LT), KH PO (KDP), KTiOPO (KTP), BaB O (BB
3 2 4 4 2 4  3 2 4 4 2 4
O)、 LiB O (LBO)、 BiB O (BIBO)、 CsLiB O (CLBO)、 KNbO (KN)などを  O), LiB O (LBO), BiB O (BIBO), CsLiB O (CLBO), KNbO (KN), etc.
3 5 3 6 6 10 3  3 5 3 6 6 10 3
適宜に選択して用いることができる。 It can select suitably and can be used.
(3)上記した実施の形態においては、 2次元フォトニック結晶層を PMMAにより形 成したが、これに限られるものではないことは勿論である。 2次元フォトニック結晶層は 、使用する入射波、出射波の波長に対して光吸収が少なぐかつ、ある程度加工性 が良！、ことが好ま 、ものである力 これを満たせば如何なる材料も使用可能である (3) In the embodiment described above, the two-dimensional photonic crystal layer is formed of PMMA, but it is needless to say that the present invention is not limited to this. The two-dimensional photonic crystal layer has little light absorption with respect to the wavelength of the incident wave and the outgoing wave to be used, and has good processability to some extent! The power that is preferred, any material can be used if this is met
。例えば、無機結晶材料、無機ガラス材料、半導体材料、有機材料 (ポリマーを含む 。；)、それらの組み合わせ材料などを適宜に選択して用いることができる。また、さらに 具体例をあげれば、例えば、 SiO、ガラス材料、 SiO系塗布膜、ガラス系塗布膜、 Ti . For example, an inorganic crystal material, an inorganic glass material, a semiconductor material, an organic material (including a polymer;), a combination material thereof, or the like can be appropriately selected and used. Further specific examples include, for example, SiO, glass material, SiO-based coating film, glass-based coating film, Ti
2 2  twenty two
O、 A1N、 AlGaN、 CaF、 Al O、 Ga Oなどがあげられる。  Examples include O, A1N, AlGaN, CaF, Al 2 O, and Ga 2 O.
2 2 2 3 2 3  2 2 2 3 2 3
(4)上記した実施の形態においては、接着剤としてアクリル系ポリマーを用いたが、 これに限られるものではないことは勿論であり、接着剤としては、有機系接着剤、無機 系接着剤、その組み合わせなどを適宜に選択して用いることができ、さらに具体的な 好ましいものとしては、例えば、エポキシ榭脂、アクリル榭脂、ポリウレタン榭脂、ポリイ ミド榭脂、シリコン榭脂、低融点ガラス、水ガラスなどを適宜に選択して用いることがで きる。  (4) In the above-described embodiment, an acrylic polymer is used as an adhesive. However, the present invention is not limited to this, and as an adhesive, an organic adhesive, an inorganic adhesive, Combinations thereof can be appropriately selected and used, and more specific preferable examples include, for example, epoxy resin, acrylic resin, polyurethane resin, polyimide resin, silicon resin, low melting glass, Water glass or the like can be appropriately selected and used.
(5)上記した実施の形態においては、下地基板として Siウェハーを用いた力 これ に限られるものではないことは勿論であり、下地基板としては、 LiNbO単結晶ウェハ (5) In the above embodiment, the force using a Si wafer as the base substrate Of course, the substrate is not limited to LiNbO single crystal wafer
3  Three
一、 GaAs単結晶基板、 SiC単結晶基板、 GaN単結晶基板、 Al O単結晶基板など 1. GaAs single crystal substrate, SiC single crystal substrate, GaN single crystal substrate, AlO single crystal substrate, etc.
2 3  twenty three
を適宜に選択して用いることができる。また、これらに他の元素が添加されていてもよ く、また他の材料などの膜が表面に形成されて 、てもよ 、。 Can be appropriately selected and used. In addition, other elements may be added to these, and films of other materials may be formed on the surface.
(6)上記した実施の形態においては、クラッド層としては SiO膜や Ag膜を用いたが  (6) In the above-described embodiment, a SiO film or an Ag film is used as the cladding layer.
2  2
、これに限られるものではないことは勿論である。即ち、クラッド層は、予め非線形光 学材料に成膜しておくだけでよいため、使用する入射波、出射波の波長に対して光 吸収が少ないという条件を満たせば如何なる材料も使用可能である。例えば、無機 結晶材料、無機ガラス材料、半導体材料、有機材料 (ポリマーを含む。）、それらの組 み合わせ材料などを用いることができ、さらに具体例をあげれば、例えば、 SiO、ガ  Of course, the present invention is not limited to this. In other words, since the cladding layer only needs to be formed in advance on a nonlinear optical material, any material can be used as long as it satisfies the condition that light absorption is small with respect to the wavelength of the incident wave and the outgoing wave to be used. . For example, inorganic crystal materials, inorganic glass materials, semiconductor materials, organic materials (including polymers), combinations thereof, and the like can be used.
2 ラス材料、 SiO系塗布膜、ガラス系塗布膜、透明ポリマー、 TiO、 A1N、 AlGaN、 C  2 Glass material, SiO coating film, glass coating film, transparent polymer, TiO, A1N, AlGaN, C
2 2  twenty two
aF、 Al O、 Ga Oなどがあげられる。また、後からこのクラッド層をエッチングなどにExamples include aF, Al 2 O, and Ga 2 O. Later, this cladding layer can be etched.
2 2 3 2 3 2 2 3 2 3
より取り除けば、より強い光閉じ込めが実現できる空気クラッドにすることも可能である If removed more, it is possible to make the air clad that can realize stronger light confinement
(7)上記した実施の形態においては、 2次元フォトニック結晶層を形成するための 加工技術として、電子線リソグラフィーおよび反応性ガスを用いた ICPドライエツチン グによるドライエッチング技術やナノインプリントリソグラフィー技術を用いた力 これに 限られるものではないことは勿論であり、他のドライエッチング技術、陽極酸化技術、 化学エッチング技術、電子ビームリソグラフィー技術、集束イオンビームリソグラフィー 技術、フオトンビームリソグラフィー技術、選択成長技術あるいはレーザー加工技術な どを適宜に選択して用いることができる。 (7) In the above-described embodiment, as a processing technique for forming the two-dimensional photonic crystal layer, a dry etching technique by electron beam lithography and ICP dry etching using a reactive gas or a nanoimprint lithography technique is used. Of course, it is not limited to this, other dry etching technology, anodizing technology, chemical etching technology, electron beam lithography technology, focused ion beam lithography technology, photon beam lithography technology, selective growth technology or laser processing Technology can be selected and used as appropriate.
(8)上記した実施の形態においては、本発明によるフォトニック結晶を深紫外波長 域や赤外波長領域に応用する場合について説明したが、これに限られるものではな V、ことは勿論であり、可視波長域や X線波長域ある!/ヽは遠赤外波長域さらにはテラへ ルツ波長領域などのような、他の波長域における波長変換技術として応用可能であ る。また、光パラメトリック増幅の原理を用いれば、同一の入射波長でも様々な波長へ 変換できるため、本発明によるフォトニック結晶を用いて、波長可変レーザ素子も実 現することができる。 (9)上記した実施の形態においては、本発明によるフォトニック結晶を非線形光学 効果を利用した波長変換に適用した場合について説明したが、これに限られるもの ではな!/、ことは勿論であり、フォトニック結晶の電場増強効果や分散関係の制御性な どの特徴を利用して、超高速光変調や光スイッチングなど非線形光学効果を利用し た他の作用効果の効率も著しく向上することができる。 (8) In the above-described embodiment, the case where the photonic crystal according to the present invention is applied to the deep ultraviolet wavelength region and the infrared wavelength region has been described. However, the present invention is not limited to this V. The visible wavelength range and the X-ray wavelength range can be applied as wavelength conversion technology in other wavelength ranges such as the far-infrared wavelength range and the terahertz wavelength range. In addition, if the principle of optical parametric amplification is used, even the same incident wavelength can be converted into various wavelengths. Therefore, a tunable laser element can be realized using the photonic crystal according to the present invention. (9) In the above-described embodiment, the case where the photonic crystal according to the present invention is applied to wavelength conversion using the nonlinear optical effect has been described. However, the present invention is not limited to this! Using the characteristics of the photonic crystal, such as the electric field enhancement effect and the controllability of the dispersion relationship, the efficiency of other effects using nonlinear optical effects such as ultrafast optical modulation and optical switching can be significantly improved. .
(10)本発明によるフォトニック結晶は、上記した実施の形態に限定されるものでは なぐフォトニック結晶内における無機非線形光学結晶層の上下関係や、フォトニック 結晶層以外の薄いコア層を本構造体に挟む構造、フォトニック結晶層の上にまた何 らかの層を積層する構造、クラッド層を入れない構造なども本発明によるフォトニック 結晶の範囲に含まれるものである。例えば、無機非線形光学結晶表面に Tiなどを拡 散することにより表面に導波路を形成でき、無機非線形光学結晶の非ドープ層自体 をクラッド層として使用することもできるものであり、その上にフォトニック結晶構造を積 むようにしたものも本発明の範囲に含まれる。また、無機非線形光学結晶の上にこれ より屈折率の高い材料 (例えば、 TiO  (10) The photonic crystal according to the present invention is not limited to the above-described embodiment, and the vertical relationship of the inorganic nonlinear optical crystal layer in the photonic crystal and the thin core layer other than the photonic crystal layer have this structure. A structure sandwiched between bodies, a structure in which any other layer is laminated on the photonic crystal layer, a structure without a cladding layer, and the like are also included in the scope of the photonic crystal according to the present invention. For example, a waveguide can be formed on the surface of the inorganic nonlinear optical crystal by diffusing Ti or the like, and the undoped layer of the inorganic nonlinear optical crystal itself can be used as a cladding layer. Those having a nick crystal structure are also included in the scope of the present invention. In addition, a material with a higher refractive index on the inorganic nonlinear optical crystal (for example, TiO
2など)で導波路コア層（その上にさらにフォト- ック結晶層を積む。）やフォトニック結晶層を作製すれば、無機非線形光学結晶がク ラッド層として働くと同時に波長変換層として働くものであり、こうしたものも本発明の 範囲に含まれる。  2) etc., if a waveguide core layer (with a photonic crystal layer on top of it) or a photonic crystal layer is prepared, the inorganic nonlinear optical crystal functions as a quad layer as well as a wavelength conversion layer. These are also included in the scope of the present invention.
(12)上記した実施の形態においては、無機非線形光学結晶層を波長レベルの厚 さ、例えば、 50mm〜10 μ m程度の厚さとした力 好ましくは、 200nm〜l μ m程度 であり、さらに好ましくは、 200〜600應である。  (12) In the above-described embodiment, the force with which the inorganic nonlinear optical crystal layer has a wavelength level thickness, for example, a thickness of about 50 mm to 10 μm, preferably about 200 nm to 1 μm, and more preferably Is between 200 and 600.
(13)上記した実施の形態ならびに上記した（1)乃至（12)に示す変形例は、適宜 に組み合わせるようにしてもょ 、。  (13) The above embodiment and the modifications shown in the above (1) to (12) may be combined as appropriate.
産業上の利用可能性 Industrial applicability
本発明は、例えば、波長変換素子、高調波発生素子、和周波 ·差周波発生素子、 光パラメトリック増幅素子、誘導ラマン散乱素子、四波混合素子、小型レーザー光源 、光スィッチ素子、光双安定素子、光論理演算素子、光変調素子あるいは位相共役 光発生素子などの各種の素子に利用することができるものであり、こうした素子を使 用することによって、小型かつ高効率な深紫外レーザー光源や赤外レーザー光源な どを実現することができるようになる。 The present invention includes, for example, a wavelength conversion element, a harmonic generation element, a sum frequency / difference frequency generation element, an optical parametric amplification element, a stimulated Raman scattering element, a four-wave mixing element, a small laser light source, an optical switch element, and an optical bistable element It can be used for various elements such as optical logic operation elements, light modulation elements, and phase conjugate light generation elements. By using these elements, small and highly efficient deep ultraviolet laser light sources and red light sources can be used. Outside laser light source Can be realized.
そして、小型高性能な深紫外レーザー光源や赤外レーザー光源が実現されると、 深紫外レーザー光源については、高集積度の次世代 DVDや光メモリ用途向け光源 、計測用 He— Cdレーザーや殺菌'露光用水銀ランプを置換する光源、さらには PC Bなどの環境汚染物質の深紫外光触媒処理法の光源としてなどの利用が見込まれ、 産業分野への多大な貢献、甚大な市場規模が期待できる。また、 DNA切断、レーザ 顕微鏡、生体分子蛍光認識用の光源としてなど、バイオ'医学への応用も強く期待さ れる。  When small high-performance deep ultraviolet laser light sources and infrared laser light sources are realized, deep ultraviolet laser light sources are highly integrated next-generation DVDs, light sources for optical memory applications, He-Cd lasers for measurement and sterilization. It is expected to be used as a light source to replace mercury lamps for exposure, and as a light source for deep ultraviolet photocatalyst treatment of environmental pollutants such as PCBs. It is also expected to be applied to biomedical applications such as DNA cleavage, laser microscope, and light source for biomolecular fluorescence recognition.
一方、赤外レーザー光源については、環境ガス、有害ガスなどのセンサー検知用 のレーザー光源や通信用のレーザ光源として、産業応用が強く期待される。  On the other hand, for infrared laser light sources, industrial applications are strongly expected as laser light sources for sensor detection of environmental gases and harmful gases, and as laser light sources for communication.

Claims

請求の範囲 The scope of the claims
[1] 上下のクラッド領域の間に、無機非線形光学結晶を含み、かつ、周期的屈折率分 布構造を与えるフォトニック結晶部を有する  [1] Between the upper and lower cladding regions, have a photonic crystal part that contains an inorganic nonlinear optical crystal and gives a periodic refractive index distribution structure
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[2] 上下にクラッド領域を有し、かつ、前記上下のクラッド領域の間に、光を導波させる 一層または複数層のコア層部を有し、かつ、前記上下のクラッド領域または前記コア 層部の少なくとも一部に、周期的屈折率分布構造を与えるフォトニック結晶部を含み 、かつ、前記上下のクラッド領域または前記コア層部の少なくとも一部に無機非線形 光学結晶を有する  [2] The upper and lower clad regions have one or more core layer portions for guiding light between the upper and lower clad regions, and the upper and lower clad regions or the core layers At least part of the part includes a photonic crystal part that gives a periodic refractive index distribution structure, and has an inorganic nonlinear optical crystal in at least part of the upper and lower cladding regions or the core layer part
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[3] 上下にクラッド領域を有し、かつ、前記上下のクラッド領域の間に、光を導波させる 一層または複数層のコア層部を有し、かつ、前記上下のクラッド領域または前記コア 層部の少なくとも一部に、 1次元または 2次元フォトニック結晶層を含み、かつ、前記 上下のクラッド領域または前記コア層部の少なくとも一部に無機非線形光学結晶層 を有する [3] The upper and lower clad regions, and one or more core layer portions for guiding light between the upper and lower clad regions, and the upper and lower clad regions or the core layers At least part of the part includes a one-dimensional or two-dimensional photonic crystal layer, and has an inorganic nonlinear optical crystal layer in at least part of the upper and lower cladding regions or the core layer part
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[4] クラッド層と、 [4] a cladding layer;
前記クラッド層の上に形成された無機非線形光学結晶層と、  An inorganic nonlinear optical crystal layer formed on the cladding layer;
前記無機非線形光学結晶層の上に形成された 1次元または 2次元フォトニック結晶 層と  A one-dimensional or two-dimensional photonic crystal layer formed on the inorganic nonlinear optical crystal layer;
を有することを特徴とするフォトニック結晶。  A photonic crystal characterized by comprising:
[5] 請求項 3または 4のいずれ力 1項に記載のフォトニック結晶において、 [5] In the photonic crystal according to any one of claims 3 or 4,
前記無機非線形光学結晶層の厚さが、光の波長レベルの厚さである  The thickness of the inorganic nonlinear optical crystal layer is a thickness at the wavelength level of light.
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[6] 請求項 3または 4のいずれ力 1項に記載のフォトニック結晶において、 [6] In the photonic crystal according to any one of claims 3 and 4,
前記無機非線形光学結晶層の厚さが、 50ηπ！〜 10 mである  The thickness of the inorganic nonlinear optical crystal layer is 50ηπ! ~ 10 m
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[7] 請求項 6に記載のフォトニック結晶において、 前記無機非線形光学結晶層の厚さが、 200ηπ！〜 1 μ mである [7] The photonic crystal according to claim 6, The thickness of the inorganic nonlinear optical crystal layer is 200ηπ! ~ 1 μm
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[8] 請求項 3、 4、 5、 6または 7のいずれ力 1項に記載のフォトニック結晶において、 前記無機非線形光学結晶層は、無機非線形光学結晶を表面研磨して薄膜形状に 形成された [8] The photonic crystal according to any one of claims 3, 4, 5, 6, or 7, wherein the inorganic nonlinear optical crystal layer is formed into a thin film shape by polishing the surface of the inorganic nonlinear optical crystal.
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[9] 請求項 3、 4、 5、 6、 7または 8のいずれ力 1項に記載のフォトニック結晶において、 前記 1次元または 2次元フォトニック結晶層は、 SiO系材料、ガラス系材料またはポ [9] The force of any one of claims 3, 4, 5, 6, 7 or 8, wherein the one-dimensional or two-dimensional photonic crystal layer is formed of a SiO-based material, a glass-based material, or a polymer.
2  2
リマー材料により形成された  Formed by limer material
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[10] 請求項 3、 4、 5、 6、 7、 8または 9のいずれか 1項に記載のフォトニック結晶において 前記無機非線形光学結晶層を構成する無機非線形光学結晶は、 LiNbO [10] The photonic crystal according to any one of claims 3, 4, 5, 6, 7, 8, or 9, wherein the inorganic nonlinear optical crystal constituting the inorganic nonlinear optical crystal layer is LiNbO.
3結晶で ある  3 crystals
ことを特徴とするフォトニック結晶。  A photonic crystal characterized by that.
[11] 非線形光学特性を有するフォトニック結晶の製造方法において、  [11] In a method for producing a photonic crystal having nonlinear optical characteristics,
クラッド層の上に無機非線形光学結晶層を形成する第 1の工程と、  A first step of forming an inorganic nonlinear optical crystal layer on the cladding layer;
前記無機非線形光学結晶層の上に 1次元または 2次元フォトニック結晶層を形成 する第 2の工程と  A second step of forming a one-dimensional or two-dimensional photonic crystal layer on the inorganic nonlinear optical crystal layer;
を有することを特徴とするフォトニック結晶の製造方法。  A method for producing a photonic crystal, comprising:
[12] 請求項 11に記載のフォトニック結晶の製造方法にぉ 、て、 [12] The method for producing a photonic crystal according to claim 11, wherein
前記第 1の工程は、前記無機非線形光学結晶層の厚さを光の波長レベルの厚さに 形成する  In the first step, the thickness of the inorganic nonlinear optical crystal layer is formed to a thickness at a wavelength level of light.
ことを特徴とするフォトニック結晶の製造方法。  A method for producing a photonic crystal characterized by the above.
[13] 請求項 11に記載のフォトニック結晶の製造方法にぉ 、て、 [13] The method for producing a photonic crystal according to claim 11, wherein
前記第 1の工程は、前記無機非線形光学結晶層の厚さを 50ηπ！〜 10 mに形成 する  In the first step, the thickness of the inorganic nonlinear optical crystal layer is reduced to 50ηπ! ~ 10 m to form
ことを特徴とするフォトニック結晶の製造方法。 A method for producing a photonic crystal characterized by the above.
[14] 請求項 13に記載のフォトニック結晶の製造方法において、 [14] The method for producing a photonic crystal according to claim 13,
前記第 1の工程は、前記無機非線形光学結晶層の厚さを 200ηπ！〜 1 μ mに形成 する  In the first step, the thickness of the inorganic nonlinear optical crystal layer is set to 200ηπ! ~ 1 μm
ことを特徴とするフォトニック結晶の製造方法。  A method for producing a photonic crystal characterized by the above.
[15] 請求項 11、 12、 13または 14のいずれ力 1項に記載のフォトニック結晶の製造方法 において、 [15] The method for producing a photonic crystal according to any one of claims 11, 12, 13 or 14, wherein
前記第 1の工程は、無機非線形光学結晶を表面研磨して前記無機非線形光学結 晶層を薄膜形状に形成する  In the first step, the inorganic nonlinear optical crystal is surface-polished to form the inorganic nonlinear optical crystal layer in a thin film shape.
ことを特徴とするフォトニック結晶の製造方法。  A method for producing a photonic crystal characterized by the above.
[16] 請求項 11、 12、 13、 14または 15のいずれ力 1項に記載のフォトニック結晶の製造 方法において、 [16] In the method for producing a photonic crystal according to any one of claims 11, 12, 13, 14, or 15, wherein
前記第 2の工程は、 SiO系材料、ガラス系材料またはポリマー材料により前記 1次  In the second step, the primary material is made of SiO-based material, glass-based material or polymer material.
2  2
元または 2次元フォトニック結晶層を形成する  Form original or two-dimensional photonic crystal layer
ことを特徴とするフォトニック結晶の製造方法。  A method for producing a photonic crystal characterized by the above.
[17] 請求項 11、 12、 13、 14、 15または 16のいずれか 1項に記載のフォトニック結晶の 製造方法において、 [17] In the method for producing a photonic crystal according to any one of claims 11, 12, 13, 14, 15, or 16,
前記第 2の工程は、 LiNbO結晶により前記無機非線形光学結晶層を形成する  In the second step, the inorganic nonlinear optical crystal layer is formed from a LiNbO crystal.
3  Three
ことを特徴とするフォトニック結晶の製造方法。  A method for producing a photonic crystal characterized by the above.
[18] 請求項 11、 12、 13、 14、 15、 16また ίま 17の!/、ずれ力 1項に記載のフォトニック結 晶の製造方法において、 [18] In the method for producing a photonic crystal according to claim 11, 12, 13, 14, 15, 16, or ί or 17!
前記第 2の工程は、前記無機非線形光学結晶層の上に前記 1次元または 2次元フ オトニック結晶層を形成するための材料を配置し、ナノインプリントリソグラフィ一により 前記材料に対して周期的構造を形成して前記 1次元または 2次元フォトニック結晶層 を形成する  In the second step, a material for forming the one-dimensional or two-dimensional photonic crystal layer is disposed on the inorganic nonlinear optical crystal layer, and a periodic structure is formed on the material by nanoimprint lithography. To form the one-dimensional or two-dimensional photonic crystal layer
ことを特徴とするフォトニック結晶の製造方法。  A method for producing a photonic crystal characterized by the above.
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