JP2000249834A - Polarizer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polarizer having excellent homogeneity and stable performance without dispersing metal particles by arranging a large number of columns produced by depositing an electrically conductive layer on the surface of a semiconductor or dielectric material in a transparent base body. SOLUTION: This polarizer 1 has a polarizing portion formed in a planer transparent base body 2 comprising one or more kinds of glass, crystals and plastics. The polarizing portion consists of columns 3 arranged at an equal distance of several 10 to several 100 nm from one another in the transparent base body 2. The column 3 consist of a surface layer of a metal thin film which is an electrically conductive layer of about 10 to 1,000 Å thickness, and an inner layer consisting of a semiconductor such as a Si single crystal or a dielectric material. The minor axis and major axis of the columns 3 are specified to 5 to 50 nm and 500 to 50,000 nm, respectively, and the aspect ratio is specified to >=10. The distance between adjacent columns is preferably controlled to 50 to 200 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizer used for an optical communication device, an optical recording device, an optical sensor, and the like, and a method for manufacturing the same, and is particularly suitable for an optical isolator used for an optical communication device. The present invention relates to a polarizer used and a method for producing the polarizer.

[0002]

2. Description of the Related Art A conventional polarizer is an element utilizing colored ions, such as a cell in which a certain kind of solution is put in a cell, a cell in which a colorant is put in a plastic, and a large number of dielectric thin films laminated on a substrate. An element utilizing interference of a multilayer thin film, a polarizing prism typified by a Glan-Thompson prism composed of a crystal having a large birefringence, a PBS (polarizing beam splitter) for separating polarization components using Brewster conditions,
Alternatively, a polarizing film that orients a polymer material in a certain direction and absorbs a polarized component in one direction has been dominant.

However, a conventional polarizer using colored ions has a large wavelength dependence, and it is necessary to select a polarizer having an optimum wavelength characteristic for each wavelength. In addition, although a polarizer composed of a crystal having a large refractive index has a small wavelength dependency, there is no polarizer having a small size and excellent wavelength characteristics so far, such as difficulty in processing and a limitation in element size, making it difficult to miniaturize. .

In recent years, a polarizing glass has been used as an optical communication device for the above-mentioned polarizer. This polarizer has a structure in which, for example, transparent glass is used as a transparent solid medium, and elliptical silver particles are aligned in a certain direction and dispersed in the medium to give anisotropy (for example, Japanese Patent Publication No. -4
No. 0619).

[0005] In this method for producing a polarizing glass, first, a glass batch comprising at least one halide selected from the group consisting of silver and chloride, bromide and iodide is melted, and a glass substrate having a required shape is melted. Mold into
Next, the glass substrate is subjected to a heat treatment under predetermined conditions to precipitate silver halide grains in the glass.

Further, the glass base is stretched by applying a tension in a predetermined temperature range, so that the silver halide grains are elongated and aligned in the tension direction. Finally, a polarizer can be obtained by exposing the stretched glass substrate to a reducing atmosphere in a defined temperature range and reducing a part of the silver halide to metal silver particles.

[0007]

However, in these production methods, in the former, heat treatment is performed in a reducing atmosphere in order to precipitate metallic silver from silver halide. As a result, it is difficult to control the amount of metallic silver precipitated in the glass substrate, and stable optical characteristics cannot be obtained. Therefore, even if the glass substrate is heated and stretched, it is difficult to stably obtain reproducible polarization characteristics.

In addition, there is a problem that the presence of a temperature distribution in the thickness direction in the glass substrate causes silver halide not reduced to metallic silver to remain in the center, which adversely affects the transmittance. .

Furthermore, when the silver halide grains are reduced to metallic silver, the volume shrinks by about 1/3, so that the surface portion of the glass substrate being reduced becomes porous, and there is a problem in long-term reliability. was there.

Therefore, a discontinuous island-like particle layer and a dielectric layer such as glass are alternately formed on a dielectric substrate such as glass by using a thin film manufacturing process such as vacuum deposition, and then anisotropically formed by heating and stretching. Some have been proposed to have the property. (Refer to the Proceedings of the IEICE Autumn National Convention 1990, C-212, etc.). In this polarizer, each island in the island-shaped metal particle layer serves as a metal particle, and has the same structure as that in which the metal particles are dispersed.

However, according to this method, the metal particles diffuse into the glass film during the lamination, and it is difficult to obtain a stable polarization characteristic. In particular, it is difficult to obtain an extinction ratio at a desired wavelength. As described above, conventional glass polarizers based on metal particle dispersion have inhomogeneous dispersion of metal particles in glass, inhomogeneous mechanical elongation of dispersed metal particles, diffusion of metal particles into glass and solidification. There was a problem in homogeneity, such as local inhomogeneity due to melting, and the lamination type had many steps, resulting in a problem in yield.

Accordingly, an object of the present invention is to provide a polarizer having excellent homogeneity and stable performance without dispersing metal particles, and a method for producing the same.

[0013]

In order to achieve the above object, a polarizer according to the present invention comprises a transparent substrate in which a large number of columnar bodies each having a conductive layer adhered to a semiconductor or dielectric surface are arranged. Consisting of

Further, the short axis length of the columnar body is 5 to 50 nm,
It is characterized in that the major axis length is 500 to 50,000 nm, and the interval between adjacent columnar bodies is 50 to 200 nm.

The columnar body is characterized in that a conductive layer of 10 to 1000 ° is formed on the surface of a dielectric made of Si.

Also, a method of manufacturing a polarizer, comprising arranging a large number of columns having light absorption anisotropy in a transparent substrate, comprising: bonding a plate made of a dielectric to a support substrate; Removing unnecessary portions from the plate-like body to form a large number of pillars, forming a conductive layer on the surface of the pillar-like body, removing a part or all of the support substrate, and removing the columnar body. Surrounding the body with a transparent substrate.

Here, a semiconductor or a dielectric refers to one having a dielectric constant of 1 or more. Further, the conductive layer is a metal (Cu, Al, Cr, Au, Ag, etc.) having a specific conductivity of 0.1 or more, preferably 0.5 or more when the conductivity of copper is set to 1.
More preferably, it is good to be 1 or more (Cu, Ag, etc.).

The numerical range for limiting the shape and the interval of the columnar body is a preferable range in which an extinction ratio of 40 dB or more can be obtained and light scattering does not easily occur.

The columnar body may be tapered at the end, and has at least a two-layer structure at the cut surface. The surface layer is a metal thin film having a thickness of about 10 to 1000 mm, and the inner layer is a single layer of Si. It is good to consist of a crystal.

Further, a specific method for producing a polarizer of the present invention is a method for producing a polarizer comprising arranging a large number of rod-shaped metal bodies having light absorption anisotropy in a transparent substrate. And a step of forming a rod-shaped metal body by coating the Si with a metal thin film, and surrounding the rod-shaped metal body with a transparent substrate.

Here, as the transparent substrate, various inorganic materials and organic materials can be used. Further, a metal thin film having light absorption anisotropy is, for example, Cu, Ni, Al, Co, F
One or more metal elements such as e, Sn, and Ag are appropriately selected, and the columnar body has an aspect ratio of 10 or more.

With these configurations, the substrate functions as a polarizer, and good polarization characteristics can be obtained.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a polarizer 1 is made of glass,
A polarizing section is provided on a plate-shaped transparent substrate 2 made of at least one of a crystal and a plastic. This polarizing section is composed of columnar bodies 3 arranged at approximately equal intervals of several tens to several hundreds of nm in a transparent substrate 2, and the columnar bodies 3 are formed of a conductive layer having a thickness of about 10 to 1000 mm as shown in FIG. It comprises a surface layer 3b made of a certain metal thin film and an inner layer 3a made of a semiconductor or dielectric such as, for example, Si single crystal. In addition, the major axis direction of the columnar body 3 faces the two main surfaces 2a and 2b of the transparent substrate 2.

Here, in order to obtain a polarizer capable of obtaining an extinction ratio of 40 dB or more and hardly causing light scattering, the short axis length of the columnar body is 5 to 50 nm and the long axis length is 500 to 5 nm.
0000 nm, the aspect ratio is 10 or more,
Further, the interval between adjacent columnar bodies is set to 50 to 200 n.
m. The transparency of the transparent substrate 2 means that the transparent substrate 2 is transparent to the light having the wavelength used by the polarizer 1, and the transparent substrate 2 is made of a glass material such as borosilicate glass or silica glass, or a material such as Ta ₂ O ₅ . One or more kinds are appropriately selected from organic materials such as a thin film dielectric and polymethyl methacrylate (PMMA). The surface layer 3b of the columnar body 3 having light absorption anisotropy is formed of Cu, Ni, Al, Co, Mn, Fe, Sn,
It is preferable that the layer is formed by appropriately selecting one or more of metal elements such as Ag.

The polarizer 1 configured as described above is provided on the substrate 2
The light L1 incident from the side surface 2b of the column 3 is absorbed in the major axis direction of the columnar body 3, and is emitted as polarized light L2 from which the major axis component is removed. The polarizer 1 having such polarization characteristics can be suitably used particularly as an optical isolator.

Hereinafter, an example of a method for manufacturing the polarizer 1 will be described with reference to FIGS.

First, as shown in FIG. 3A, a Si wafer 12 is bonded to a glass substrate 11, for example. Next, as shown in FIG. 3B, after the Si wafer 12 is made extremely thin to 1 μm or less, the Si surface is covered with a mask material 13 made of SiO ₂ , Si ₃ N _4, etc. To form The mask material 13 is appropriately selected from substances having resistance to the etching solution of Si. By etching the masked Si, a columnar body (inner layer) 3a as shown in FIG. 3C is formed. The columnar body 3a thus obtained is coated with a surface layer 3b, which is a conductive layer of a metal or the like, by various thin film forming methods such as an electron beam evaporation method, thereby forming a columnar body as shown in FIG. Body 3 can be obtained. Next, as shown in FIG. 3E, the transparent base material is overcoated, and the columnar body 3 is surrounded by the transparent base 2. Such an overcoat is mainly formed by a thin film forming method, but a relatively low-temperature process such as a sol-gel method is preferably performed. Finally, a desired polarizer 1 as shown in FIG. 3F can be obtained by removing unnecessary portions and performing a surface treatment by a CMP method or the like.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Example 1 A Si wafer having a thickness of 400 μm and having a (100) or (110) plane as a main surface and a thickness of 1 m
m aluminosilicate glass (SiO ₂ : 55.3% by weight, A
l ₂ O ₃ : 22.9% by weight, B ₂ O ₃ : 7.4% by weight, Mg
O: 8.5 wt%, CaO: 4.7 wt%, Na ₂ O: 0.6
% By weight, K ₂ O: 0.4% by weight) at 400 ° C. and -1200.
The electric field bonding was performed under the condition of V.

Next, the CMP method (Chemical and Mechanica)
l Polishing), flattening and polishing were performed to a thickness of about 1.0 μm of Si. On the ultra-thin single-crystal Si obtained in this manner, by photolithography using Si ₃ N ₄ as a mask material, an interval of about 50 nm, an interval of about 300 nm
Grid was formed. When this was subjected to anisotropic etching using a KOH solution, a large number of trapezoidal Si single crystals having a diameter of about 50 nm were formed at intervals of about 400 nm. Then, using a sputtering apparatus, metal Cu was overcoated on the surface of the trapezoidal Si single crystal by about 20 nm in thickness. Thus, a rod-shaped Cu metal body having a diameter of about 80 nm was formed. Boron silicate glass (Corning 7740) was sputter-deposited to a thickness of 1 μm on the glass substrate on which the rod-shaped Cu metal body was erected, and the rod-shaped Cu metal body was completely coated with borosilicate glass. Finally, unnecessary portions were removed from the sample substrate thus obtained, and a molding process was performed to produce a polarizer having a size of 3 × 3 mm. When the polarization characteristics were measured, the extinction ratio was 45 dB and the insertion loss was 0.
It exhibited an excellent characteristic value of 08 dB.

Example 2 SIMOX (Separation by implanted oxygen) having a (110) plane having a thickness of 300 μm as a main surface
The wafer and BK7 glass having a thickness of 0.5 mm were anodically bonded in the same manner as in Example 1 to remove the Si substrate and the buried oxide film. As a result, a thin film S having a thickness of 0.2 μm was formed on a glass substrate.
An i single crystal was formed. A width of about 10 nm and an interval of about 50 nm are formed on this single crystal Si by a scanning tunneling microscope (STM).
Was drawn. Next, using this anodic oxide film as a mask, Si was etched with a hydrazine solution to form a large number of columnar Si single crystals having a diameter of about 8 nm at intervals of about 70 nm. Next, using a sputtering apparatus, metal Ni was overcoated on the surface of the single crystal Si having a thickness of about 20 nm.
Thus, a rod-shaped Ni metal body having a diameter of about 30 nm was formed. A glass of the same composition as the substrate was sputtered on the glass substrate on which the rod-shaped Ni metal body was erected, by 0.3 μm,
The rod-shaped Ni metal body was completely embedded in the glass. Finally, remove unnecessary parts from the sample substrate, and mold to 3 × 3
A polarizer having a size of mm was produced. As a result, the extinction ratio of 49
Excellent polarization characteristics of dB and insertion loss of 0.05 dB were obtained.

Example 3 A 350 μm thick (110) bonded SOI (Silicon on Insulator) substrate and silica glass were joined in the same manner as in Example 1, and S
The i-substrate and the oxide film were removed.

As a result, a thin film Si single crystal having a thickness of 0.4 μm was formed on the silica glass substrate.

A nanopattern was drawn on this single-crystal Si using STM in the same manner as in Example 2, and silicon was etched to form a large number of columnar Si single crystals having a diameter of about 15 nm at intervals of about 200 nm. Next, using a sputtering apparatus, metal Al was overcoated on the surface of the single crystal Si having a thickness of about 30 nm. Thus, a rod-shaped Al metal body having a diameter of about 50 nm was formed. Using this as a substrate, sputtering was carried out using a magnetron sputtering apparatus with Ta as a target in an atmosphere of Ar + O ₂ , and coated with a thin film of Ta ₂ O ₅ having a thickness of about 0.8 μm. When the polarization characteristics of the polarizer of the same size manufactured in this way were evaluated, the extinction ratio was 45 dB, the insertion loss was 0.09 dB, and the characteristics were at a practical level.

Example 4 The same wafer and glass substrate as in Example 2 and Co as the metal were used. Ten polarizing elements having a thickness of 0.2 μm were manufactured by the same manufacturing method, and these were joined. A polarizer having a thickness of about 2 μm was manufactured. When the polarization characteristics of the polarizer thus manufactured were evaluated, the extinction ratio was 42 dB and the insertion loss was 0.1 dB.

[0037]

As described in detail above, according to the polarizer and the manufacturing method of the present invention, the columnar body arranged in the transparent substrate makes it possible to obtain a polarized light having high uniformity which is hardly obtained by the conventional method and has almost no variation. Can provide children.

In addition, since there is no conventional process such as a stretching process or a laminating process that greatly affects polarization characteristics in a subsequent process, stable quality and a high yield can be obtained.

Further, since a Si wafer is used as a raw material, an established LSI semiconductor process can be used as it is, and a nanometer-order processing can be performed by applying a silicon micromachining process. And a highly accurate and inexpensive polarizer can be provided.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view schematically showing a polarizer according to the present invention.

FIG. 2 is a perspective view schematically illustrating a columnar body of a polarizer according to the present invention.

3 (a) to 3 (f) are cross-sectional views schematically showing steps of manufacturing a polarizer according to the present invention.

[Explanation of symbols]

 1: polarizer 2: transparent substrate 3: columnar body 3a: inner layer 3b: surface layer

Claims (4)

[Claims] 1. A polarizer comprising a transparent substrate and a large number of columnar members each having a conductive layer applied to a surface of a semiconductor or a dielectric arranged on a transparent substrate. 2. A column having a minor axis length of 5 to 50 nm,
2. The polarizer according to claim 1, wherein the major axis length is 500 to 50,000 nm, and an interval between adjacent columnar bodies is 50 to 200 nm. 3. 3. The polarizer according to claim 1, wherein the columnar body is formed by forming a conductive layer of 10 to 1000 ° on a surface of a dielectric made of Si. 4. A method for producing a polarizer, comprising arranging a large number of columns having light absorption anisotropy in a transparent substrate,
A step of joining a plate made of a dielectric to a support substrate, a step of forming unnecessary columns from the plate to form a large number of columns, and a step of forming a conductive layer on the surface of the column. Removing part or all of the support substrate and enclosing the columnar body with a transparent substrate.