JPH06148425A - Infrared polarizer and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide the infrared polarizer, which is manufactured at low cost and reducible in element size and thickness and can utilize reflected light, and its manufacture. CONSTITUTION:On the surface of a 1st substrate 11 which has a successive waveform shape wherein planes and curved surfaces successively alternate on the top surface and is transparent in an infrared light range, an optical element 12 which performs polarized separating operation in the infrared light range, and an optical element 15 which performs infrared light reflecting or absorbing operation is formed on the curved surfaces; and the surface of the 1st substrate 11 which has the waveform shape is covered with a material which is transparent in another infrared light range and made flat the surface of the 1st substrate 11 which has the waveform shape is connected to a 2nd substrate 16 which is transparent in the infrared light range. Further, an optical element which has reflection prevention characteristics can be formed on the opposite surface from the surface having the waveform shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizer for extracting linearly polarized light from natural light, and particularly to an infrared polarizer used for infrared optical elements such as optical switches and optical isolators in the infrared region. And its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, infrared polarizers are composed of (1) pile-of-plates polarizer using surface reflection of many dielectric plates, and (2) many parallel conductor line arrays (grids). There are grid polarizers.

A conventional infrared polarizer will be described below with reference to the drawings. First, the pile of plates polarizer will be described. FIG. 8 is a diagram showing a pile-of-plates polarizer, in which a large number of transparent plates 80 made of selenium (Se), polyethylene, or the like are stacked and the Brewster angle (θb) with respect to the incident light 81. If so, the transmitted light 82 becomes almost P-polarized light, and only the S-polarized light can be obtained from the reflected light 83 from the transparent plate 80.

Next, a large number of parallel conductor wire arrays (grids)
The infrared polarizer configured by will be described. This is one in which a conductor (grid) such as gold is provided on the surface of a substrate such as silicon that is transparent to infrared light at a pitch shorter than the wavelength of incident light. An example of the configuration is shown in FIG. Silicon (S
A multilayer antireflection film 92 is formed on both sides of a substrate 91 made of i), and a gold grid 93 is provided on one side of the substrate 91 at a pitch shorter than the wavelength of incident infrared light. The parallel polarized component (P polarized light) 95 is reflected and the vertical polarized component (S polarized light) 96 is transmitted.

[0005]

In the above-mentioned conventional infrared polarizer, the pile-of-plates polarizer requires many transparent plates to be stacked in parallel, which leads to an increase in size of the device. It will be expensive. In addition, an infrared polarizer composed of a large number of parallel conductor wire arrays (grids) uses a photolithographic exposure method and an ion beam etching method as its manufacturing method, but this manufacturing method has complicated steps. The device also becomes expensive.

In view of the above problems, the present invention provides an infrared polarizer which can be manufactured at low cost, can utilize reflected light, and can be made smaller and thinner, and a manufacturing method thereof.

[0007]

In order to solve the above-mentioned problems, the infrared polarizer of the present invention comprises a first substrate which is transparent in the infrared region and has a corrugated shape in which flat surfaces and curved surfaces are alternately continuous on the surface. The optical element that has a polarization separation effect in the infrared region is provided on the surface including the flat surface of the substrate, and the infrared light reflection function or the infrared light is reflected on the surface of the curved surface or the surface of the substrate facing the curved surface. An optical element having an absorbing effect can be provided.

Further, the corrugated surface of the first substrate is
The surface can be flattened by combining with a transparent substrate in the infrared region, or the corrugated surface can be covered with a transparent material in the infrared region to be planarized. As a method for combining the first substrate and the second substrate into one body, a method of bonding with an adhesive, or a method of combining the first substrate with the second substrate
It is preferable that the substrates of (1) and (2) are bonded by pressure. Also, as a method of coating the surface of the corrugated shape with a material transparent in the infrared region,
After coating the surface by a method such as coating with a material, it is preferable to cure the surface in some cases. By flattening the corrugated surface in this way, the incident light and the reflected light become parallel, and it becomes easy to broaden the effect of the optical element having the polarization separation action.

It is preferable that the refractive index of the second substrate and the refractive index of the infrared transparent material covering the surface of the second substrate be substantially the same as the refractive index of the first substrate.

The substrate of the infrared polarizer is silicon (S
i), semiconductor materials such as germanium (Ge) that are transparent in the infrared region, or silver chloride (AgCl), silver bromide (Ag)
Br) or other transparent silver halide in the infrared region, or
It can be composed of chalcogen glass that is transparent in the infrared region.

Further, the optical element having a polarized light separating action in the infrared region can be formed of a multilayer film of a dielectric and a semiconductor. As the material for forming the multilayer film, ZnS, ZnS
e, CaF2, BaF2, Sb2 O3, BiF3, Pb
Substances transparent in the infrared region such as F2, Si and Ge are suitable.

Further, the optical element having the infrared light reflecting action can be formed of a metal film. As a material forming the metal film, it is preferable to use a metal having a high reflectance for infrared light, such as Al, Ag, Au, or Cu. The dielectric film and the metal film can be formed by a method such as a vacuum deposition method and a sputtering method.

A coating material containing a black pigment or the like is preferable for the optical element having an infrared ray absorbing function, and this can be formed by a method such as a spraying method.

Although it is necessary to process the surface of the first substrate into a corrugated shape, processing the surface by conventional cutting or the like is not an appropriate method considering mass productivity. In this case, a material that is transparent in the infrared region, for example, a silver halide such as silver chloride (AgCl) or silver bromide (AgBr) or a pressable material such as chalcogen glass is processed in advance into a desired corrugated surface. By press molding with a die, a good substrate with good reproducibility can be obtained.

Therefore, the infrared polarizer uses silver halide or chalcogen glass as a substrate material, and press-molds it with a die whose surface is processed into a corrugated shape in which planes and curved surfaces are alternately continuous. After that, it can be manufactured by forming an optical element having a polarization separation action in the infrared region on the surface of the corrugated shape of the substrate transferred, and further bonding it to the second substrate with an adhesive. Can be integrated into one body, or can be combined with the second substrate by pressure bonding to form one body. Alternatively, the corrugated shape may be covered with a material transparent in the infrared region to form a flat surface.

[0016]

According to the above construction, the infrared polarizer of the present invention has the following functions. (1) An optical element having a polarization separation effect on the plane of the surface of the first substrate transmits only a linearly polarized light component in a specific direction of incident infrared light and reflects a linearly polarized light component orthogonal thereto to generate infrared light. It has the performance as a polarizer. Moreover, the reflected linearly polarized light component is further reflected by the facing surface having the same incident surface as the first reflected surface and returns to the incident direction, so that the reflected infrared light component can also be used. (2) A thin infrared polarizer can be realized by making the corrugated shape of the substrate surface minute. (3) An optical element having an infrared light reflecting action or an infrared light absorbing action can be formed on a curved surface or on a flat surface of a substrate facing the curved surface, and an infrared polarizer having an excellent extinction ratio can be obtained. (4) An infrared polarizer having excellent optical characteristics can be obtained by forming an optical element having antireflection characteristics on the surface opposite to the corrugated surface. (5) The infrared polarizer of the present invention can be mass-produced inexpensively by using a substrate obtained by press-molding a transparent material in the infrared region. (6) By combining the first substrate and the second substrate into one body, or by coating the corrugated shape of the first substrate with a transparent material in the infrared region to form a flat surface, the effective wavelength range is increased. It is possible to realize an infrared polarizer in which the incident light and the emitted light are parallel to each other easily and easily.

[0017]

EXAMPLES Examples of the infrared polarizer of the present invention will be described below.
A description will be given with reference to the drawings.

[0018]

[Table 1]

FIG. 1 shows the structure (cross-sectional view) of an infrared polarizer of Example 1 of the present invention, and 11 is made of silicon (Si) having a corrugated surface in which planes and curved surfaces are alternately continuous in the x direction. The first substrate 12 is an optical element having a polarized light separating action in the infrared region and is composed of a multilayer film of germanium (Ge) and antimony sulfide (Sb2 S3). Table 1 shows the structure of the multilayer film.

The multilayer film was formed by a vacuum vapor deposition method. Further, in order to improve the extinction ratio (T⊥ / (T (material) + T⊥)) of the polarizer, an optical element 15 having a light absorbing action by a paint using a black pigment is formed on the curved surface of the silicon substrate surface. . After that, the first substrate 11 is replaced with another second substrate 1
Combined with 6 to make one. The second substrate 16 is a substrate made of the same material having the same corrugated surface as the first substrate 11, that is, a substrate made of silicon (Si), and 18 is formed by connecting the first substrate and the second substrate together. It is an adhesive layer for The refractive index of the adhesive layer is almost equal to the refractive index of the substrate.

The waveform shape is θ1 = θ2 = 4 in FIG.
5 °, d1 = d2 = 80 .mu.m, d3 = d4 = 5 .mu.m. FIG. 5 shows the spectral transmittance characteristics of the polarizer of the present embodiment (however,
It does not include the surface reflection / absorption of the substrate, and shows the characteristics of the polarization splitting part). In FIG. 5, T (material) and T⊥ are the characteristics of linearly polarized light components orthogonal to each other, T (material) is a linearly polarized light component parallel to the incident surface, and T⊥ is a linearly polarized light component perpendicular to the incident surface.

The operation of the infrared polarizer constructed as above will be described. Of the infrared light 10 incident on the slope A of the corrugated flat surface at an incident angle of 45 °, the linearly polarized light component 14 parallel to the incident surface is transmitted and the linearly polarized light component 13 perpendicular to the incident surface is formed on the slope A. After being reflected by the optical element having the polarized light separating action in the infrared region, the light is incident on the slope B facing the slope A. The slope A and the slope B have a common incident surface. Therefore, since the infrared light 13 that has entered the slope B is a linearly polarized light component that is perpendicular to the slope B, the infrared light that is reflected by an optical element that has a polarization splitting effect in the infrared region formed on that surface is incident in the direction in which it is incident. Go back. Infrared light incident on other surfaces behaves similarly. In addition, since infrared light that is incident on a portion other than the slope of the flat surface is absorbed by the optical element that has an infrared light absorbing action, as a result, the linearly polarized light component in a specific direction of the infrared light that has entered the infrared polarizer. Through.

Further, a single-layer antireflection film 17 made of ZnS, which also serves as a protective film, is formed on the corrugated opposite surfaces of the first substrate and the second substrate. Since Si has a refractive index of 3.3, the transmittance without an antireflection film is about 5
Although it is 5%, it can be improved to about 89% at maximum by forming an antireflection film of ZnS.

The characteristics of the infrared polarizer of this example are shown in FIG. 5, and the characteristics of extinction ratio 1/200 or less were obtained at wavelengths of about 5800 to 7500 nm.

However, extinction ratio = T⊥ / (T (material) + T⊥)
Is. Next, a second embodiment of the present invention will be described.

FIG. 2 shows the structure of an infrared polarizer according to Example 2 of the present invention. Reference numeral 21 is a germanium-based chalcogen glass substrate having a corrugated surface in which planes and curved surfaces are alternately continuous in the x direction, and 22 is polarized light. It is an optical element having a separating action, and is composed of a multilayer film of germanium (Ge) and zinc sulfide (ZnS). The multilayer film was formed by a vacuum deposition method. The waveform shape of the substrate is shown in FIG. 2 as follows: θ1 = θ2 = 45 °, d1 = d2 =
100 μm and d3 = d4 = 5 μm. The curvature of the curved surface portion is about 3.5 μm.

Table 2 shows the structure of the optical element 22 having the polarized light separating action formed in this embodiment. Here, the optical film thickness is the product of the film thickness and the film refractive index, and λ0 is the reference wavelength of the optical film thickness. Further, an antireflection film 25 which also serves as a protective film was formed on the flat surface side of the substrate 21.

The infrared polarizer of this embodiment has a refractive index of 3.
The germanium-based chalcogen glass of No. 0 is press-molded with a die whose surface has a desired corrugated shape, that is, the same shape as that of FIG. 2, to obtain a substrate, after which the corrugated shape of the substrate is transferred. An optical element having a polarized light separating action in the infrared region is formed on the formed surface. Since the surface of the mold had a smooth corrugated shape, the mold and the chalcogen glass material were easily released, and a good substrate without defects such as chipping was obtained.

[0029]

[Table 2]

FIG. 6 shows the spectral transmittance characteristics of the infrared polarizer of the present embodiment (however, the characteristics of the polarization splitting portion are not included in the surface reflection / absorption of the substrate). In FIG. 6, T // and T⊥ are characteristics of linearly polarized light components orthogonal to each other, T // is a linearly polarized light component parallel to the incident surface, and T⊥ is a linearly polarized light component perpendicular to the incident surface.

The characteristics of the infrared polarizer are shown in FIG.
A characteristic of extinction ratio of 1/15 or less was obtained at 250 nm. However, extinction ratio = T⊥ / (T // + T⊥).

However, in the case of the infrared polarizer of this embodiment, FIG.
As shown in, the incident angle θ0 and the refraction angle θS with respect to the slope of the incident light are n0 · sin θ0 = nS · sin θS (where n0 and nS are the refractive indices of the incident medium and the outgoing medium, respectively) according to Snell's law. Therefore, the incident light at θ 0 = 45 ° is θ
Since S = 45 ° is not achieved, the incident light 20 and the outgoing light 24 are not parallel. Therefore, the emitted lights of the lights incident on the opposite slopes are not parallel to each other, so that caution is required in use.

In this embodiment, chalcogen glass is used as the substrate material, but silver chloride (AgCl) or other silver halide which is transparent and moldable in the infrared region may be used instead.

Next, a third embodiment of the present invention will be described.
FIG. 3 shows the structure of an infrared polarizer according to Example 3 of the present invention, which uses the same substrate 31 as the first substrate used in Example 2 above, and has a corrugated surface (Table 3). Is a polarizer formed by forming an optical element 32 having a polarized light separating action in the infrared region as shown in (1) and combining it with another second substrate 36, where 36 is the same material as the first substrate, That is, it was a chalcogen glass substrate, and was pressed and integrated with the corrugated surface of the first substrate.

In order to improve the extinction ratio, an optical element 35 having a function of absorbing infrared light is formed on the surface facing the curved surface by a paint using a black pigment. After that, a protective film 37 also serving as an antireflection film was formed on both planes as in Example 2.

[0036]

[Table 3]

The spectral transmittance characteristics of the polarizer (however, the characteristics of the polarization splitting portion not including the surface reflection / absorption of the substrate, are as shown in FIG. 7) are shown in FIG. According to Snell's law, the incident light is n0 · sin θ
Since 0 = nS.sin .theta.S and n0 = nS, .theta.0 = .theta.S, which is parallel.

Next, a fourth embodiment of the present invention will be described.
FIG. 4 shows the structure of an infrared polarizer according to Example 4 of the present invention. The same substrate 41 as the first substrate used in Example 3 is used, and Example 3 is formed on the corrugated surface. Same (Table 3)
Optical element 4 having polarized light separating action in the infrared region as shown in
2 is formed, and the surface is covered with an organic material 43 which is transparent in the infrared region instead of being bonded to the second substrate and cured to form a flat surface. In order to improve the extinction ratio, aluminum (A) is used as an optical element having an infrared light reflecting action on the plane of the first substrate facing the curved surface portion.
The metal film 44 of 1) is formed by vacuum deposition to a thickness of about 1 μm
Then, an antireflection film 45 which also serves as a protective film was formed on the flat surface. The spectral transmittance characteristics of the polarizer (however, the characteristics of the polarization splitting portion, which does not include the surface reflection / absorption of the substrate, are the same as in Example 3, are shown in FIG. 7.

The optical elements having the infrared polarized light separating action, the infrared light reflecting action, the infrared light absorbing action, and the antireflection action are not limited to those of the above-mentioned respective embodiments, and may be designed according to the design. Optical elements having respective functions may be used. When it is necessary to select the wavelength, an optical element having wavelength selection characteristics may be formed on the surface of the substrate.

[0040]

As described above, according to the present invention, in the infrared region on the surface including the flat portion of the first substrate which is transparent in the infrared region and has a corrugated shape in which flat and curved surfaces are alternately continuous. Since an infrared polarizer is provided by providing an optical element having a polarization separating action, it is possible to easily and inexpensively realize an infrared polarizer which can utilize reflected light. Further, by making the waveform shape minute, the device can be made smaller and thinner, and infrared polarizers of various sizes can be realized. Further, by using a substrate formed of silver halide or chalcogen glass, mass productivity is excellent. In this infrared polarizer, an extinction ratio can be improved by providing an optical element having an infrared light reflecting action or an infrared light absorbing action on the surface of the curved surface portion or on a plane facing the curved surface.

Further, the first substrate and the second substrate may be bonded or pressure-bonded with an adhesive to be integrated, or the corrugated shape of the first substrate may be covered with a material transparent in the infrared region. Can be a flattened infrared polarizer.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of an infrared polarizer according to Example 1 of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of an infrared polarizer according to Example 2 of the present invention.

FIG. 3 is a sectional view showing the configuration of an infrared polarizer according to Example 3 of the present invention.

FIG. 4 is a sectional view showing the structure of an infrared polarizer according to Example 4 of the present invention.

FIG. 5 is a spectral transmittance characteristic diagram of the infrared polarizer of Example 1 of the present invention.

FIG. 6 is a spectral transmittance characteristic diagram of an infrared polarizer of Example 2 of the present invention.

FIG. 7 is a spectral transmittance characteristic diagram of an infrared polarizer according to Example 3 of the present invention.

FIG. 8 is a pile of one of conventional infrared polarizers.
Plates block diagram

FIG. 9 is a configuration diagram of a grid polarizer, which is one of conventional infrared polarizers.

[Explanation of symbols]

 11, 21, 31, 41 First substrate 12, 22, 32, 42 Optical element 16, 36 Second substrate 18 Adhesive layer 15, 35, 44 Optical element 17, 25, 37, 45 Antireflection film 43 Transparent material

Claims (18)

[Claims] 1. An optical element having a polarization separating action in the infrared region is provided on a surface including a plane portion of a first substrate which is transparent in the infrared region and has a corrugated shape in which planes and curved surfaces are alternately continuous. Infrared polarizer. 2. An optical element having a polarization separating action in the infrared region is provided on the surface including the plane portion of the first substrate which is transparent in the infrared region and has a corrugated shape in which flat surfaces and curved surfaces are alternately continuous. An infrared polarizer in which the corrugated surface of the first substrate is combined with a substrate transparent in the second infrared region to form an integral body. 3. An optical element having a polarization separating action in the infrared region is provided on the surface including the flat portion of the first substrate which is transparent in the infrared region and has a corrugated shape in which planes and curved surfaces are alternately continuous. An infrared polarizer in which the corrugated shape of the first substrate is covered with a transparent material in the infrared region to be flat. 4. The second transparent substrate in the infrared region has a refractive index of the first
The infrared polarizer according to claim 2, wherein the refractive index of the substrate is substantially the same. 5. The infrared polarizer according to claim 3, wherein the refractive index of the transparent material in the infrared region is substantially equal to the refractive index of the first substrate. 6. An optical element having an infrared light reflecting action or an infrared light absorbing action is provided on the surface of the curved surface portion.
The infrared polarizer according to any one of 1. 7. The optical element having an infrared light reflecting action or an infrared light absorbing action is provided on the surfaces of the first and second substrates facing the curved surface portion. Infrared polarizer. 8. The infrared polarizer according to claim 1, wherein the substrate is made of a semiconductor material transparent in the infrared region. 9. The substrate comprises silver halide.
The infrared polarizer according to any one of 1. 10. The infrared polarizer according to claim 1, wherein the substrate is made of chalcogen glass which is transparent in the infrared region. 11. The infrared polarizer according to claim 1, wherein the optical element having a polarization separating action in the infrared region is composed of a dielectric and semiconductor multilayer film. 12. The infrared polarizer according to claim 6, wherein the optical element having an infrared light reflecting action is made of a metal film. 13. The infrared polarizer according to claim 6 or 7, wherein the optical element having an infrared light absorbing function comprises a coating film containing a pigment. 14. A silver halide is used as a material for a first substrate, which is press-molded with a die whose surface is processed into a corrugated shape in which planes and curved surfaces are alternately continuous. A method for producing an infrared polarizer, wherein an optical element having a polarization separating action in the infrared region is formed on a surface on which a wavy shape is transferred. 15. A chalcogen glass is used as a material for a first substrate, and the chalcogen glass is press-molded by a die having a corrugated shape in which a surface and a curved surface are alternately continuous, and then the corrugated substrate is corrugated. A method for producing an infrared polarizer, in which an optical element having a polarized light separating action in the infrared region is formed on the surface on which the above shape is transferred. 16. A first substrate, which has an optical element having a polarization separation action in the infrared region on the surface of a substrate having a corrugated shape in which planes and curved surfaces are alternately continuous on the surface, and the first substrate. A method for manufacturing an infrared polarizer, wherein a second substrate having substantially the same surface shape is bonded with an adhesive to be integrated. 17. A first substrate and a second substrate, which have an optical element having a polarization separating action in the infrared region formed on the surface of a substrate having a corrugated shape in which planes and curved surfaces are alternately continuous on the surface, are pressure-bonded to each other. A method for manufacturing an infrared polarizer that is bonded and integrated. 18. A substrate having a corrugated shape in which planes and curved surfaces are alternately continuous on the surface, and an optical element having a polarization separating action in the infrared region is formed on the surface of the substrate, and the surface of the first substrate is transparent in the infrared region. First with corrugated shape by coating with material
Manufacturing method of an infrared polarizer for flattening the surface of a substrate.