JPH04355702A - Infrared polarizer - Google Patents

Abstract

PURPOSE:To provide the polarizer of a thin type for IR light which is inexpensive and has excellent heat resistance and weatherability by forming a thin film having a polarization sepn. effect on an Si substrate worked to a saw tooth shape. CONSTITUTION:An optical element 12 having the polarization sepn. effect is formed on the 1st Si substrate 11 having the saw tooth section and is stuck to an Si substrate 13 having the same saw tooth-shaped surface as the saw tooth-shaped surface of the 1st substrate 11 via an adhesive layer 14. The polarizer of the thin type for IR light which reflects the specific component in the incident light to an incident direction, is inexpensive and has the excellent heat resistance and weatherability is obtd. by this constitution.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared polarizer for extracting linearly polarized light from infrared light.

0002

[Prior Art] Conventionally, infrared polarizers include (1) a polarizer that utilizes the phenomenon that polarized light components are separated by arranging a large number of dielectric plates so as to form a Brewster angle θ0 with respect to incident light; For example, there are pile-of-plates, and (2) a grid polarizer composed of a large number of parallel conductor wire arrays (grits).

A conventional infrared polarizer will be explained below with reference to the drawings. FIG. 4 shows the structure of a pile-of-plates polarizer. As shown in the figure, it is constructed by laminating transparent plates 20 made of selenium (Se), polyethylene, or the like. When the transparent plate 20 is installed so as to form a Brewster angle θ0 with respect to the incident light 21, most of the transmitted light 22 becomes only P-polarized light. Also, reflected light 2 from the transparent plate 20
3, only S-polarized light is obtained when the Brewster angle is θ0. Next, a grid polarizer constituted by a large number of parallel conductor wire arrays (grits) will be explained. FIG. 5 shows the configuration of a grid polarizer. As shown in the figure, silicon (Si
) A multilayer anti-reflection film 25 is formed on both sides of the substrate 24, and on one side thereof, a submicron pitch (pitch shorter than the wavelength of incident light) grid 26 made of a thin gold film is provided. Of the incident light 27, a polarization component (P polarization) 28 parallel to the grid is reflected, and a polarization component (S polarization) 28 perpendicular to the grid is reflected.
9 is transparent.

0004

However, such a conventional pile-of-plates polarizer has a disadvantage in that the device becomes large because a large number of transparent plates are superimposed in parallel. Grit polarizers, which are composed of a large number of parallel conductor wire arrays (grits), are manufactured using photographic exposure and ion beam etching, but these methods require complicated manufacturing processes. Moreover, in terms of cost, it cannot be said to be an inexpensive polarizer.

The present invention solves these problems by providing an infrared polarizer that can utilize reflected light, has excellent weather resistance, can be made smaller and thinner, and can be manufactured at a lower cost. The purpose is to

[0006]

[Means for Solving the Problems] In order to achieve the above object, the polarizer of the present invention has a sawtooth surface of a first substrate having a sawtooth-like continuous uneven cross-sectional shape on the surface. The structure is such that an optical element is provided on the top and has a polarization separation effect in the infrared light region.

[0007] Further, the polarizer is constructed by bonding a second substrate having the same sawtooth cross-sectional structure as another first substrate with the optical element thin film sandwiched therebetween. It is something. Further, the first and second substrates are made of silicon (S
The optical element consisting of (i) and having a polarization separation function is formed of a multilayer film mainly composed of a dielectric material and a semiconductor.

[0008]

[Function] In the above configuration, the optical element having a polarization separation function transmits only the linearly polarized component of the incident infrared light in a specific direction, and reflects the linearly polarized component orthogonal to the linearly polarized component. Moreover, since the substrate surface has a sawtooth shape, the reflected linearly polarized light component is further reflected by the opposing surface having the same incident surface as the first reflecting surface and returns in the direction from which it was incident. Here, since the substrate surface is serrated, a thin polarizer can be realized. Furthermore, since a thin film having a polarization separation effect is formed on a Si substrate processed into a sawtooth shape, it can be manufactured at low cost, and an infrared polarizer with excellent weather resistance can be realized.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An infrared polarizer according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1(A) shows the structure of an infrared polarizer according to a first embodiment of the present invention, and FIG. 1(B) shows a structure of an infrared polarizer according to a first embodiment of the present invention.
The cross-sectional structure of the sawtooth portion of the board is shown. As shown in Figures 1 (A) and (B), the surface of the Si substrate with a sawtooth cross section in the Forms a multilayer film. The shape of the sawtooth is θ1 = θ2 = 45° and d1 = 100 μm, as shown in FIG. 1(B). Table 1 shows the configuration of the optical element 2 having a polarization separation function.

[0011]

[Table 1]

Next, the operation of the polarizer constructed as described above will be explained. For example, the sawtooth slope A of the sawtooth part
Of the infrared light 3 that is incident at an incident angle of 45°, the linearly polarized component 5 parallel to the plane of incidence is transmitted, and the linearly polarized component 4 perpendicular to the plane of incidence is reflected by the slope A and then returns to face the slope A. It is incident on slope B. Since slope A and slope B have a common incident surface, the light 14 incident on slope B is a linearly polarized light component perpendicular to slope B, and is further reflected by that surface and returns in the direction of incidence. Since light incident on other surfaces behaves similarly, as a result, only the linearly polarized component in a specific direction of the light incident on the polarizer is transmitted.

As described above, by providing an optical element having a polarization separation function on the sawtooth surface of the first substrate, which has a sawtooth cross-sectional shape in a specific direction, linearly polarized light components in a specific direction can be transmitted. , it is possible to realize a polarizer that reflects a linearly polarized light component perpendicular to the linearly polarized light component in the direction in which it is incident on the polarizer.

(Embodiment 2) FIG. 2(A) shows the structure of a polarizer according to a second embodiment of the present invention, and FIG. 2(B) shows the cross-sectional structure of the sawtooth portion. As shown in FIGS. 2(A) and 2(B), a multilayer film of germanium (Ge) and antimony sulfide (Sb2S3) is formed on the sawtooth surface of the first Si substrate 11, which has a sawtooth cross section in the x direction in the figure. An optical element 12 having a polarization separation function is provided. A Si substrate 13 having the same sawtooth surface as the first substrate is bonded to the first substrate 11 via an adhesive layer. The shape of the sawtooth part shown in Fig. 2(B) is θ1 = θ2 = 45°, d1 = 100μ
It is m.

FIG. 3 shows the spectral transmittance characteristics of the infrared polarizer of the second embodiment. In FIG. 3, a and b are the spectral characteristics of orthogonal linearly polarized light components, respectively. The action of the polarizer configured as above is the same as that of the first embodiment,
Of the light incident on the polarizer, a linearly polarized component in a specific direction is reflected in the incident direction, and a linearly polarized component perpendicular to the incident direction is transmitted. Furthermore, by adopting the configuration as in the second embodiment, the refractive index of the incident medium to the optical element having a polarization separation function can be set high, so that the effective wavelength range as a polarizer can be widened. .

[0016] Furthermore, on the Si substrate processed into a sawtooth shape,
Since a thin film having a polarization separation effect is formed, it can be manufactured at low cost. Furthermore, it is possible to realize a thin infrared polarizer that has excellent heat resistance and weather resistance.

It should be noted that the present invention is not limited to the shapes of the first and second embodiments, and an optimal shape can be selected in consideration of the effective wavelength range, the size of the polarizer, etc.

[0018]

As is clear from the description of the embodiments above, according to the present invention, polarized light is provided on the surface of the sawtooth portion of a Si substrate having a sawtooth cross-sectional shape in a specific direction. Since the polarizer is constructed by providing an optical element having a separating function, a thin infrared polarizer with excellent heat resistance and weather resistance can be realized at a low cost.

[Brief explanation of drawings]

FIG. 1 (A) is a perspective view of a polarizer of Example 1 of the present invention (
B) is a cross-sectional view of the sawtooth part of Example 1

FIG. 2 (A) is a perspective view of a polarizer according to Example 2 of the present invention (
B) is a cross-sectional view of the sawtooth part of Example 2

[Figure 3] Diagram showing polarization characteristics of the polarizer of Example 2

[Figure 4]
Perspective view of pile of plates, a conventional infrared polarizer

[Figure 5] Perspective view of the same grid polarizer

[Explanation of symbols]

1, 11, 13 Si substrate 2, 12 with sawtooth cross section
Optical element with polarization separation effect 3 Incident infrared light 4 Reflected light 5 Transmitted light 14 Adhesive layer

Claims (5)

[Claims] 1. Polarized light for infrared light, comprising: a sawtooth surface of a first substrate having a sawtooth cross-sectional shape on the surface thereof; and an optical element having a polarization separation function in the infrared light region on the surface of the substrate; Child. 2. A first substrate provided with an optical element on its surface and another second substrate, the optical element being sandwiched between the two and bonded together,
The infrared polarizer according to claim 1, which is integrally constructed. 3. The first and second substrates each having a sawtooth cross-sectional shape on their surfaces are made of silicon.
The infrared polarizer according to any one of the above. 4. The infrared polarizer according to claim 2, wherein the second substrate has the same sawtooth surface as the first substrate. 5. The infrared polarizer according to claim 1, wherein the optical element having a polarization separation function comprises a multilayer film of a dielectric and a semiconductor.