JP2009128879A - Optical isolator using photonic crystal and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical isolator which is thinner and more compact than heretofore by forming a polarizer and a wavelength plate on the same substrate surface. <P>SOLUTION: Cyclic trenches are produced on the substrate by electron beam lithography and dry etching (S1). Data for constitution design of the polarizer and the wavelength plate are obtained in order to alternately laminate multilayers on the substrate while maintaining cyclic rugged shapes in an x-axis direction of each layer by combining sputtering deposition and sputtering etching (S2). Based on the data for constitution design obtained at processing S2, an antireflection film is formed on the substrate and film-forming processing of laminating the multilayers which becomes the polarizer of a photonic crystal is performed (S3). Similarly based on the data for constitution design obtained at processing S2, the antireflection film is formed on the multilayers of the polarizer which is film-formed at processing S3 and film-forming processing of laminating the multilayers which become the wavelength plate of the photonic crystal is performed (S4). Thereby the optical isolator is manufactured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical isolator using a photonic crystal that achieves an isolator function by a combination of a wave plate and a polarizing element by one optical element (one surface on one side) manufactured from the photonic crystal, and its manufacture. It is about the method.

  Conventionally, in an optical communication system or the like, light emitted from a semiconductor laser used as a light source is reflected by an optical component arranged on the optical path of the emitted light, and return light is generated by light traveling in the reverse direction on the optical path. When this return light returns to the semiconductor laser and enters, it causes unstable operation such as output, frequency fluctuation, modulation band suppression, and LD breakdown. In order to prevent this, an optical isolator, which is an optical element that allows light to pass only in one direction, is disposed and used between the light source and the optical component on the optical path. Patent Document 1 discloses an optical isolator that is used in the field of optical storage, optical communication, and the like and reduces the return light to the semiconductor laser and stabilizes the laser oscillation intensity of the semiconductor laser.

  In addition, as a method for detecting a glossy image of an object having glossiness, a reflected light image from an object irradiated with illumination light is captured using an optical isolator comprising a polarizer and a quarter-wave plate, and Patent Document 2 describes that a reflected light image from an object irradiated with illumination light without using an optical isolator is captured, and a glossy image of the object is detected by subtraction processing between both reflected light images. .

  The pickup optical system used for DVD, CD, BD (Blu-ray Disc: registered trademark), HD-DVD (High-Definition DVD) and the like as shown in FIG. 8 includes a semiconductor laser 20 as a light source, a polarization beam splitter 21. , A quarter wavelength plate 22, a deflection prism 23, and an objective lens 24.

In this pickup optical system, the P-polarized light of the laser beam from the semiconductor laser 20 passes through the polarizing beam splitter 21 and the quarter-wave plate 22 and is condensed on the medium 25 by the objective lens 24, and the presence or absence of a groove in the medium 25 is checked. The ¼ wavelength plate 22 and the polarizing beam splitter 21 are reversed as reflected light and act as an S-polarized signal. The combination of the polarization beam splitter and the quarter wavelength plate provides a function as an optical isolator and contributes to the stability of the semiconductor laser.
JP 2007-225905 A Japanese Patent No. 3306513 JP 2001-108832 A

  In the wave plate described above, for example, a half-wave plate (phase difference 180 deg) is used to rotate linearly polarized light, and the rotation angle is adjusted by the angle formed between the incident polarized light and the slow axis. By setting the slow axis to 45 degrees, the plane of polarization rotates by 90 degrees, and in the quarter wave plate (phase difference 90 deg), linearly polarized light is used to convert circularly polarized light or circularly polarized light into linearly polarized light. Similarly, circularly polarized light can be obtained by setting the slow axis to 45 degrees with respect to linearly polarized light.

  For this reason, in order to obtain the function as an optical isolator, it is necessary to impose a restriction on the angle (shifting the optical axis by 45 degrees) between the quarter wavelength plates combined with the polarizer and the polarization beam splitter. There is a problem that it is difficult to make the optical isolator compact.

  The present invention is directed to solving the problems of the prior art, and a photonic that can realize a thinner and more compact optical isolator than the prior art by forming a polarizer and a wave plate on the same surface on the same substrate. An object is to provide an optical isolator using a crystal and a method for manufacturing the same.

  In order to achieve the above object, an optical isolator using a photonic crystal according to claim 1 according to the present invention includes a transparent substrate having a periodic concavo-convex structure in one direction and two or more types of transparent having different refractive indexes. A first periodic structure made of a multi-layer photonic crystal having a body laminated on an uneven structure, and a multi-layer photonic made by laminating two or more types of transparent bodies having different refractive indexes on the first periodic structure And a second periodic structure made of a crystal.

  An optical isolator using a photonic crystal according to claims 2 and 3 is the optical isolator according to claim 1, wherein the transparent substrate has a unidirectional periodic concavo-convex structure on each of the front surface and the back surface. The first and second periodic structures are formed on one surface of the substrate, the wave plate of the periodic structure is formed on the other surface, and the first and second periodic structures are polarized. The element and the other have the function of a wave plate.

  The optical isolator using the photonic crystal according to claim 4 is a multilayer film in which a transparent substrate having a periodic concavo-convex structure in one direction and two or more types of transparent bodies having different refractive indexes are laminated on the concavo-convex structure. A first periodic structure made of a photonic crystal is a polarizer, and a second period made of a multi-layer photonic crystal in which two or more types of transparent bodies having different refractive indexes are stacked on the first periodic structure. The structure is a wave plate, and the polarizer and the wave plate function as an isolator corresponding to the same wavelength.

  An optical isolator using a photonic crystal according to claim 5 is a multilayer film in which a transparent substrate having a periodic concavo-convex structure in one direction and two or more types of transparent bodies having different refractive indexes are laminated on the concavo-convex structure. A first periodic structure made of a photonic crystal is a wave plate, and a second period made of a multi-layer photonic crystal in which two or more types of transparent bodies having different refractive indexes are stacked on the first periodic structure. The structure is a polarizer, and the wave plate and the polarizer function as an isolator corresponding to the same wavelength.

  The optical isolator using the photonic crystal according to any one of claims 6 to 8 is the optical isolator according to any one of claims 1 to 5, wherein the first periodic structure and the second periodic structure are stacked on the transparent substrate. An antireflection film is disposed between the transparent substrate and the periodic structure, and an antireflection film is formed on the surface of the periodic structure laminated on the transparent substrate. It is characterized by arranging.

The optical isolator using the photonic crystal according to claim 9 or 10 is the optical isolator according to claims 1 to 8, wherein an antireflection film is disposed on the back surface of the surface on which the periodic structure of the transparent substrate is formed. Further, the transparent body laminated as a multilayer film forming the periodic structure is composed of any one of SiO _2, Al ₂ O _3, Ta ₂ O _5, Nb ₂ O ₅ and TiO _2. And

  The method for manufacturing an optical isolator using a photonic crystal according to claim 11 includes a step of forming a periodic concavo-convex structure in one direction of the transparent substrate, and a refractive index of the refractive index on the concavo-convex structure as a first periodic structure. A step of forming a multilayer film made of a photonic crystal by laminating two or more different types of transparent bodies, and two or more types of transparent bodies having different refractive indexes on the first periodic structure as a second periodic structure. A step of forming a multilayer film made of a photonic crystal by laminating the first and second periodic structures on the same surface of the transparent substrate.

  The method for manufacturing an optical isolator using a photonic crystal according to claims 12 and 13 is the method for manufacturing an optical isolator according to claim 1, wherein in the step of forming the periodic uneven structure in one direction of the transparent substrate, A periodic uneven structure is formed on each of the front and back surfaces of the substrate, the first and second periodic structures are formed on one surface of the transparent substrate, and the wavelength plate of the periodic structure is formed on the other surface. Further, the first and second periodic structures are characterized in that one has a function of a polarizer and the other has a function of a wave plate.

  The method for manufacturing an optical isolator using a photonic crystal according to claim 14 includes a step of forming a periodic concavo-convex structure in one direction of a transparent substrate, and a concavo-convex structure as a polarizer of the first periodic structure. A step of forming a multilayer film made of a photonic crystal by laminating two or more types of transparent bodies having different refractive indexes, and 2 having different refractive indexes on the first periodic structure as a wavelength plate of the second periodic structure. It consists of a process of forming a multilayer film made of photonic crystals by laminating more than one type of transparent body, and the polarizer and wave plate laminated on the same surface of the transparent substrate function as an isolator corresponding to the same wavelength. Features.

  The method for manufacturing an optical isolator using a photonic crystal according to claim 15 includes a step of forming a periodic concavo-convex structure in one direction of a transparent substrate, and a wave plate of the first periodic structure on the concavo-convex structure. A step of forming a multilayer film made of a photonic crystal by laminating two or more types of transparent bodies having different refractive indexes, and 2 having different refractive indexes on the first periodic structure as a polarizer of the second periodic structure. It consists of a step of forming a multilayer film made of photonic crystals by laminating more than one type of transparent body, and the wave plate and the polarizer laminated on the same surface of the transparent substrate function as an isolator corresponding to the same wavelength. Features.

  The method for manufacturing an optical isolator using a photonic crystal according to any one of claims 16 to 18 is the method for manufacturing an optical isolator according to any one of claims 11 to 15, wherein the first periodic structure laminated on a transparent substrate and Having a step of forming an antireflection film between the two periodic structures, further having a step of forming an antireflection film between the transparent substrate and the periodic structure, and laminating on the transparent substrate And a step of forming an antireflection film on the surface of the periodic structure.

The method for manufacturing an optical isolator using a photonic crystal according to claims 19 and 20 is the optical isolator manufacturing method according to claims 1 to 18, wherein the optical isolator is reflected on the back surface of the surface on which the periodic structure of the transparent substrate is formed. The transparent body to be laminated as a multilayer film for forming the periodic structure has any of SiO _2, Al ₂ O _3, Ta ₂ O _5, Nb ₂ O _5, and TiO ₂ . It is characterized by comprising.

  According to the above configuration and method, two functions of a polarizer and a wave plate can be formed on the same surface of the substrate using a photonic crystal.

  According to the present invention, the functions of the polarizer and the wave plate are implemented by stacking photonic crystals, and the two functions are configured by stacking photonic crystals on the same surface of the substrate. In addition, since it is manufactured integrally, there is no need for adjustment, assembly, etc., and it is possible to reduce the occurrence of defects associated with this work and the reduction in manufacturing yield.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view showing a structure of a photonic crystal in an embodiment of the present invention, and is a cross-sectional view seen from a direction orthogonal to a continuous periodic structure so that a periodic uneven structure in one direction can be seen. The structure of FIG. 1 has periodicity in the horizontal direction (x direction) and vertical direction (z direction), and no periodicity in the depth direction (y direction) not shown.

  In FIG. 1, reference numeral 1 denotes a transparent substrate, which has a periodic uneven structure in one direction. Reference numeral 2 denotes a low refractive index layer corresponding to a part of the multilayer film 4 having a laminated periodic structure. Reference numeral 3 denotes a high refractive index layer corresponding to a part of the multilayer film 4 having a laminated periodic structure. Such a periodic structure is a one-dimensional photonic crystal if it is a structure having periodicity in one axial direction due to a difference in periodicity in the axial direction, and a dichroic filter or PBS made by laminating optical thin films in multiple layers. Filters have been known for a long time. A structure having periodicity in the biaxial direction becomes a two-dimensional photonic crystal, and the structure in FIG. 1 is this two-dimensional photonic crystal. A structure having periodicity in the three-axis direction is a three-dimensional photonic crystal, and has a three-dimensional optical axis in a plurality of directions.

The photonic crystal of the present invention has a function as a wave plate. In the case of a two-dimensional photonic crystal, the optical characteristics are mainly determined by the parameters described below. In FIG.
1. 1. Refractive index of the transparent substrate 1 2. Refractive index of the low refractive index layer 2 Film thickness dL of the low refractive index layer 2
4). 4. Refractive index of the high refractive index layer 3 Film thickness dH of high refractive index layer 3
6). Period P of periodic uneven structure
7). Inclination θv of periodic uneven structure (V-shaped)
And 8. 8. Number of layers or period of lamination of the high refractive index layer 3 and the low refractive index layer 2 Film thickness dL and film thickness dH for every lamination period
The parameters configured as described above are matched with values that provide desired characteristics.

In the present embodiment, the transparent thin film to be laminated is based on a combination of a low refractive index material and a high refractive index material. For example, SiO ₂ and Ta ₂ O ₅ , SiO ₂ and Nb ₂ O ₅ , SiO ₂ A combination of TiO ₂ , SiO ₂ and Al ₂ O ₃ , Al ₂ O ₃ and Ta ₂ O ₅ , Al ₂ O ₃ and Nb ₂ O ₅ , Al ₂ O ₃ and TiO _2, or the like may be used.

  In the photonic crystal of the present invention, the transparent substrate 1 on which the periodic concavo-convex structure is formed is introduced into a film forming apparatus shown in FIG. 2 having an etching source, for example. This film forming apparatus is a film forming apparatus that forms a thin film of a target material on a substrate by sputtering a target as shown in the schematic diagram of FIG. 2, and is provided in the vacuum chamber 10 and the vacuum chamber 10. A cylindrical substrate holder 11, an etching source 12, and a first target 13, a second target 14, and a reaction source 15 that are provided inside the vacuum chamber 10 and are partitioned by a shielding plate. The inside of the vacuum chamber 10 is evacuated by an exhaust system (not shown) and kept in a high vacuum state. The cylindrical substrate holder 11 can be rotated at a predetermined rotational speed, and one or a plurality of transparent substrates 1 can be held on the outer periphery of the substrate holder 11 (see Patent Document 3: FIG. 3).

  Etching is performed on the rectangular periodic concavo-convex structure on the transparent substrate 1 introduced into the film forming apparatus to form a V-shaped periodic concavo-convex structure. Further, a raw material (first target) of a high refractive index material is sputtered (deposited) to form the high refractive index layer 3 on the transparent substrate 1 so as to have a desired film thickness. At this time, the etching source is operated at the same time, and the etching effect by plasma is applied to shape the same shape as the V-shaped periodic uneven structure formed on the substrate.

  Subsequently, the raw material (second target) of the low refractive index material is sputtered (deposited) to form the low refractive index layer 2 on the transparent substrate 1 so as to have a desired film thickness. At this time, the above-described etching source is operated at the same time, and an etching effect by plasma acts to shape the same shape as the V-shaped periodic uneven structure formed on the substrate. Thereafter, the above-described film formation of the high-refractive index material and the low-refractive index material is repeated until the desired number of layers is reached, but the film thickness of each layer is controlled to a film thickness based on the design value to produce a photonic crystal.

Here, a specific example is given and demonstrated about this embodiment. First, the transparent substrate used in the embodiment is a cycle in one direction in a fine processing in which an electron beam resist is applied to a quartz substrate, a fine line is drawn by electron beam drawing, and the resist is developed and then dry etching is performed. A transparent substrate with a concavo-convex structure is produced. The transparent substrate has a groove width of 200 nm and a groove depth of 100 nm. The above-mentioned transparent substrate 1 was held on the substrate holder 11 by the film forming apparatus shown in FIG. 2, and the vacuum chamber 10 in the apparatus was evacuated to 1 × 10 ⁻⁴ Pa or less. Ar gas is introduced into the etching source 12, the ion beam source is activated to irradiate the transparent substrate 1 with the Ar ion beam, and the rectangular shape of the transparent substrate 1 is processed into a V-shaped periodic uneven structure (see FIG. 1). ). At this time, Ar gas was introduced at 100 sccm, and an electric power of 2.5 kw was supplied to the etching source 12.

Subsequently, 200 sccm of Ar gas is introduced from the vicinity of the first target 13 (Si target), 7 kW of power is introduced to the cathode of the first target 13, and an Si film is formed on the transparent substrate 1 very thinly. At this time, simultaneously with the film formation of Si, 100 sccm of oxygen is introduced into the reaction source 15 (oxidation source), and further 5 kw of electric power is supplied to irradiate oxygen plasma and radicals onto the transparent substrate 1. Si is oxygenated to form a SiO ₂ thin film. Thereafter, Ar gas is introduced into the etching source 12, the ion beam source is activated, and the SiO ₂ thin film formed on the transparent substrate 1 is irradiated with the Ar ion beam to form a V-shaped periodic concavo-convex structure. . At this time, the film thickness of the SiO ₂ thin film was adjusted to 50 nm to form a film.

Further, Ar gas is introduced at 200 sccm from the vicinity of the second target 14 (Nb target), 5 kW of electric power is introduced into the cathode of the second target 14, and an Nb film is formed on the transparent substrate 1 very thinly. At this time, simultaneously with the Nb film formation, oxygen 100 sccm is introduced into the reaction source 15 (oxidation source), and further 5 kw of electric power is supplied to irradiate oxygen plasma and radicals onto the transparent substrate 1. Nb is oxygenated to form a thin film of Nb ₂ O ₅ . Thereafter, Ar gas is introduced into the etching source, the ion beam source is activated, and the Nb ₂ O ₅ thin film formed on the substrate is irradiated with the Ar ion beam to form a V-shaped periodic uneven structure. At this time, the Nb ₂ O ₅ thin film was adjusted to have a film thickness of 50 nm, and the film was formed.

The process of molding the SiO ₂ thin film and the Nb ₂ O ₅ thin film was alternately repeated 26 times, and finally the SiO ₂ thin film molding process was performed to form a total of 53 layers.

  As described above, the photonic crystal wave plate in which the multilayer film was formed on the transparent substrate 1 was measured with a phase difference measuring device. As a result, the phase difference at a wavelength of 405 nm was 135 deg.

  Subsequently, a multilayer film was formed on the photonic crystal wave plate to form a photonic crystal polarizer. The multilayer film can be continuously produced by the same apparatus as the wave plate described above.

After forming the wave plate, 200 sccm of Ar gas is introduced from the vicinity of the second target 14 (Nb target), 5 kw of power is introduced to the cathode of the second target 14, and the Nb film is extremely thin on the transparent substrate 1. Form a film. At this time, simultaneously with the Nb film formation, oxygen 100 sccm is introduced into the reaction source 15 (oxidation source), and further 5 kw of electric power is supplied to irradiate oxygen plasma and radicals onto the transparent substrate 1. Nb is oxygenated to form a thin film of Nb ₂ O ₅ . Thereafter, Ar gas is introduced into the etching source 12, the ion beam source is activated, and the Nb ₂ O ₅ film formed on the transparent substrate 1 is irradiated with the Ar ion beam to form a V-shaped periodic uneven structure. Mold. At this time, the Nb ₂ O ₅ thin film was adjusted to have a thickness of 200 nm, and the film was formed.

Subsequently, 200 sccm of Ar gas is introduced from the vicinity of the first target 13 (Si target), 7 kW of power is introduced to the cathode of the first target 13, and an Si film is formed on the transparent substrate 1 very thinly. At this time, simultaneously with the film formation of Si, 100 sccm of oxygen is introduced into the reaction source 15 (oxidation source), and further 5 kw of electric power is supplied to irradiate oxygen plasma and radicals onto the transparent substrate 1. Si is oxygenated to form a SiO ₂ thin film. Thereafter, Ar gas is introduced into the etching source 12 and the ion beam source is operated to irradiate the SiO 2 thin film formed on the transparent substrate 1 with the Ar ion beam to form a V-shaped periodic uneven structure. At this time, the film thickness of the SiO ₂ thin film was adjusted to 240 nm to form a film.

The process of forming the Nb ₂ O ₅ thin film and the SiO ₂ thin film was repeated 25 times alternately to form a total of 50 multilayer films.

  When the function of this photonic crystal layer is confirmed using the optical system shown in FIG. 3, the return light from the reflection surface of the medium 25 is reflected by the photonic crystal surface and has the same function as that shown in FIG. It was confirmed. This photonic crystal layer functions as an optical isolator having functions of a polarizer and a wave plate.

  FIG. 5 is a cross-sectional view showing the configuration of the optical isolator of this embodiment. As shown in FIG. 5, for example, the first photonic crystal layer 6a has a quarter wavelength via the antireflection film (first, second, and third antireflection layers 5a, 5b, and 5c) on the transparent substrate 1. It is a figure which shows the structure arrange | positioned so that a board and the 2nd photonic crystal layer 6b may function as a polarizer.

  In addition, the first photonic crystal layer 6a may be a polarizer and the second photonic crystal layer 6b may be a wave plate, not limited to the configuration described above. Even if the S shape is formed in the same direction, an optical isolator can be manufactured, and the same effect can be obtained.

  FIG. 6 is a flowchart for explaining a manufacturing process of an optical isolator using a photonic crystal in the present embodiment. As shown in FIG. 1, as the material processing, periodic grooves are manufactured on the transparent substrate 1 by electron beam lithography and dry etching using the film forming apparatus of FIG. 2 (S1).

For example, using a SiO ₂ and Si target on this transparent substrate 1, combining sputter deposition and sputter etching, and laminating multilayer films alternately while preserving the periodic uneven shape in the x-axis direction of each layer, Data on the design of the polarizer and wave plate is acquired (S2).

  Based on the data of the structural design acquired in the process S2, an antireflection film is formed on the substrate, and a film forming process for stacking a multilayer film to be a polarizer of the photonic crystal is performed (S3).

  Similarly, based on the structural design data obtained in process S2, an antireflection film is formed on the polarizer multilayer film formed in process S3, and a multilayer film serving as a photonic crystal wave plate is laminated. Film processing is performed (S4). Thereby, an optical isolator is manufactured.

  FIG. 7 is a flowchart showing a process for acquiring data for designing the configuration of the polarizer and the wave plate in the above-described process S2. In FIG. 7, first, parameters for acquiring data used for configuration design are input (S11). As this parameter, the refractive index, film thickness, shape interval (pitch) in the materials used for each layer forming the photonic crystal, and the angle, height, width, etc. as shown in FIG. 1 are used.

  Using the input parameters, light scattering, diffraction, etc. are simulated on a computer. For example, data to be calculated and configured by a finite difference time domain method such as the FD-TD method (Finite Difference Time-Domain Method) is acquired (S12). Data is obtained from the calculation result and the configuration of the polarizer is designed (S13). For example, according to a band diagram composed of phase information for each wavelength derived from the structural design, the structural design of the polarizer is performed by combining the configurations in which the band gap is generated.

  The polarization separation characteristics of the designed polarizer are confirmed (S14). The polarization separation characteristic in this case indicates the transmittance when linearly polarized light is incident in parallel with the optical axis of the polarizer and when incident in an orthogonal state. The parallel state is the transmittance of TM (P wave), and the orthogonal state is the transmittance of TE (S wave). As a confirmation method, for example, a plurality of data of polarizers that have been configured and designed in advance are obtained in advance by experimentally measuring and measuring characteristics for each of a plurality of parameters, and compared with data acquired by configuration design. To confirm. Here, in the case of OK, “TM transmittance ≧ specific value transmittance, TE transmittance ≦ specific value transmittance”, and in the case of NG, “TM transmittance ≦ specific value transmittance, TE Transmittance ≧ transmittance of specification value ”. In this process S14, when it is determined as NG, the process returns to process S1 and reprocesses with another parameter.

  In this way, the design is performed using the layer thickness (film thickness) as a parameter, and the phase difference per cycle (lamination) is calculated, and “(phase difference of specification value (target value)) / (phase difference per cycle) is calculated. ) = (Required period (number of layers)) ”. Therefore, a desired phase difference can be obtained by adjusting the number of layers and the film thickness (designed as parameters).

  Next, after processing the polarizer, the wave plate is similarly obtained from the calculation result and the wave plate is designed (S15). In accordance with a band diagram composed of phase information for each wavelength derived from the configuration design, the configuration of the wave plate is designed by combining configurations that do not generate a band gap and have a phase difference.

  Here, as the phase difference of the wave plate, in the photonic crystal wave plate in which thin films are periodically formed in multiple layers, the birefringence having the optical axis in the longitudinal direction of the groove is generated due to the structural anisotropy. Therefore, when light is incident from the direction perpendicular to the plane and the polarization of the incident light is linearly polarized at 45 degrees with respect to the groove, the polarization of the emitted light is rotated by 90 degrees with respect to the incident polarized light. Is given a half-wave phase difference. Similarly, when a multilayer film having four periods is laminated, the phase difference becomes a quarter wavelength, and linearly polarized light is converted into circularly polarized light. Thus, the phase difference changes depending on the number of stacked photonic crystals.

  Further, the polarization separation characteristics of the structurally designed wave plate are confirmed (S16). As a confirmation method, the same method as that of the polarizer in step S14 is performed. When it is determined as NG, the process returns to step S1 and re-processing is performed using another parameter.

  The optimization design of the antireflection layer arranged between the substrate, the polarizer and the wave plate is performed (S17). As this optimization design, for example, a model of a polarizer and a wave plate is formed with a simulator, and an antireflection film (first, second, and third reflections) shown in FIG. The material and film thickness for forming the prevention layers 5a, 5b, 5c) in the middle of the transparent substrate 1, the first photonic crystal layer 6a, the second photonic crystal layer 6b, and air are selected, and the structural design is completed.

  As described above, in an optical isolator in which a polarizer using a photonic crystal plate and a wave plate are stacked, two functions are formed on the same surface of the substrate, and a thin and compact optical isolator can be realized. In addition, since it is manufactured integrally, it is not necessary to adjust the position of the polarizer and the wave plate, or to assemble, and it is possible to reduce the occurrence of defects associated with this work and the reduction in manufacturing yield.

  In the optical isolator using the photonic crystal and the manufacturing method thereof according to the present invention, the functions of the polarizer and the wave plate are performed by stacking photonic crystals, and the two functions are stacked on the same surface of the substrate. The optical isolator can be made thinner and more compact than before, and because it is manufactured in one piece, there is no need to adjust and assemble the polarizer and wave plate. This can be reduced, and is useful for an isolator formed by combining a wave plate and a polarizing element on one optical element (one surface on one side).

The figure which shows the outline of the periodic structure in embodiment of this invention Diagram showing schematic configuration of film deposition system Diagram showing the optical system for confirming the function of the photonic crystal layer The figure which shows the optical system which formed the polarizer and the waveplate in one Sectional view showing configuration of optical isolator Flow chart of optical isolator manufacturing process Flow chart showing data acquisition process for designing the configuration of polarizer and wave plate Diagram showing schematic configuration of pickup optical system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Low refractive index layer 3 High refractive index layer 4 Multilayer film 5a First antireflection layer 5b Second antireflection layer 5c Third antireflection layer 6a First photonic crystal layer 6b Second photonic crystal layer 7 Wavelength Plate 8 Photonic crystal layer 10 Vacuum chamber 11 Substrate holder 12 Etching source 13 First target 14 Second target 15 Reaction source 20 Semiconductor laser 21 Polarizing beam splitter 22 1/4 wavelength plate 23 Deflection prism 24 Objective lens 25 Medium

Claims (20)

  A transparent substrate having a periodic concavo-convex structure in one direction, a first periodic structure formed of a multi-layer photonic crystal in which two or more types of transparent bodies having different refractive indexes are laminated on the concavo-convex structure, and the refractive index An optical isolator using a photonic crystal comprising: a second periodic structure made of a multi-layer photonic crystal in which two or more different types of transparent bodies are stacked on the first periodic structure .   The transparent substrate has a unidirectional periodic concavo-convex structure on each of the front and back surfaces, the first and second periodic structures are formed on one surface of the transparent substrate, and the periodic structure is formed on the other surface. 2. An optical isolator using a photonic crystal according to claim 1, wherein a wave plate is formed.   3. The optical isolator using a photonic crystal according to claim 1, wherein one of the first and second periodic structures has a function of a polarizer and the other has a function of a wave plate.   A first periodic structure made of a multi-layer photonic crystal in which a transparent substrate having a periodic uneven structure in one direction and two or more kinds of transparent bodies having different refractive indexes are laminated on the uneven structure is a polarizer, A second periodic structure made of a multi-layer photonic crystal in which two or more types of transparent bodies having different refractive indexes are laminated on the first periodic structure is a wave plate, and the polarizer and the wave plate Is an optical isolator using a photonic crystal, which functions as an isolator corresponding to the same wavelength.   The wavelength plate is a first periodic structure made of a multi-layer photonic crystal in which a transparent substrate having a periodic uneven structure in one direction and two or more types of transparent bodies having different refractive indexes are laminated on the uneven structure, A second periodic structure made of a multi-layer photonic crystal in which two or more types of transparent bodies having different refractive indexes are laminated on the first periodic structure is a polarizer, and the wavelength plate and the polarizer Is an optical isolator using a photonic crystal, which functions as an isolator corresponding to the same wavelength.   6. The antireflection film is disposed between the first periodic structure and the second periodic structure laminated on the transparent substrate. 6. Optical isolator using photonic crystal.   The optical isolator using a photonic crystal according to claim 1, wherein an antireflection film is disposed between the transparent substrate and the periodic structure.   The optical isolator using a photonic crystal according to any one of claims 1 to 7, wherein an antireflection film is disposed on a surface of the periodic structure laminated on the transparent substrate.   9. An optical isolator using a photonic crystal according to claim 1, wherein an antireflection film is disposed on the back surface of the surface on which the periodic structure of the transparent substrate is formed. . The transparent body laminated as a multilayer film forming the periodic structure is composed of any one of SiO _2, Al ₂ O _3, Ta ₂ O _5, Nb ₂ O ₅ and TiO _2. An optical isolator using the photonic crystal according to any one of 1 to 9.   A step of forming a periodic concavo-convex structure in one direction of a transparent substrate and a multilayer film made of a photonic crystal by laminating two or more kinds of transparent bodies having different refractive indexes on the concavo-convex structure as a first periodic structure And a step of forming a multilayer film made of a photonic crystal by laminating two or more types of transparent bodies having different refractive indexes on the first periodic structure as the second periodic structure, A method of manufacturing an optical isolator using a photonic crystal, wherein the first and second periodic structures are stacked on the same surface of the transparent substrate.   In the step of forming the periodic concavo-convex structure in one direction of the transparent substrate, the periodic concavo-convex structure is formed on each of the front surface and the back surface of the transparent substrate, and the first and second periods are formed on one surface of the transparent substrate. 12. The method of manufacturing an optical isolator using a photonic crystal according to claim 11, wherein the structure is formed, and the wave plate of the periodic structure is formed on the other surface.   13. The method of manufacturing an optical isolator using a photonic crystal according to claim 11, wherein one of the first and second periodic structures has a function of a polarizer and the other has a function of a wave plate.   A step of forming a periodic concavo-convex structure in one direction of the transparent substrate, and a multilayer made of a photonic crystal by laminating two or more kinds of transparent bodies having different refractive indexes on the concavo-convex structure as a polarizer of the first periodic structure Forming a film, and forming a multilayer film made of a photonic crystal by laminating two or more kinds of transparent bodies having different refractive indexes on the first periodic structure as a wave plate of the second periodic structure A method of manufacturing an optical isolator using a photonic crystal, wherein the polarizer and the wave plate stacked on the same surface of the transparent substrate function as an isolator corresponding to the same wavelength.   A step of forming a periodic concavo-convex structure in one direction of a transparent substrate, and a multilayer made of a photonic crystal by laminating two or more transparent bodies having different refractive indexes on the concavo-convex structure as a wavelength plate of the first periodic structure Forming a film, and forming a multilayer film made of a photonic crystal by laminating two or more kinds of transparent bodies having different refractive indexes on the first periodic structure as a polarizer of the second periodic structure A method of manufacturing an optical isolator using a photonic crystal, wherein the wave plate and the polarizer laminated on the same surface of the transparent substrate function as an isolator corresponding to the same wavelength.   16. The method according to claim 11, further comprising a step of forming an antireflection film between the first periodic structure and the second periodic structure laminated on the transparent substrate. A method of manufacturing an optical isolator using the photonic crystal described in 1.   The method of manufacturing an optical isolator using a photonic crystal according to any one of claims 11 to 16, further comprising a step of forming an antireflection film between the transparent substrate and the periodic structure.   The optical isolator using a photonic crystal according to any one of claims 11 to 17, further comprising a step of forming an antireflection film on a surface of the periodic structure laminated on the transparent substrate. Production method.   19. The photonic crystal according to claim 11, further comprising a step of forming an antireflection film on a back surface of the surface on which the periodic structure of the transparent substrate is formed. Manufacturing method of optical isolator. The transparent body laminated as a multilayer film forming the periodic structure is composed of any one of SiO _2, Al ₂ O _3, Ta ₂ O _5, Nb ₂ O ₅ and TiO _2. 20. A method for manufacturing an optical isolator using the photonic crystal according to any one of 11 to 19.

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