JPS61233329A - Polarized light detector - Google Patents

Abstract

PURPOSE:To constitute a device into an integral structure and to facilitate handling by making the pitch of materials constituting a wire grating shorter than a half wavelength of the light to be detected and making their width longer than 60% of the pitch. CONSTITUTION:A wire grating 3 consisting of plural light-nontransmissive material stripes parallel with one another is provided on the light receiving face 2 of a semiconductor light receiver 1. The pitch of light-nontransmissive materials constituting the wire grating 3 is made shorter than a half wavelength of the light to be detected and their width is made longer than 60% of the pitch. A polarized light in the direction parallel with the direction of the wire grating 3 is intercepted and only a polarized light in the direction perpendicular to the direction of the wire grating 3 is made incident on the receiver 1. Thus, the device is handled easily with the integral structure.

Description

[Detailed Description of the Invention] [Summary] A plurality of non-light-transmitting strips (hereinafter referred to as wire gratings) are arranged such that a plurality of non-light-transmitting strips (hereinafter referred to as wire gratings) are arranged so as to correspond to the direction of an electric vector of light incident thereon.
on the light-receiving surface of a semiconductor light-receiving device by taking advantage of the characteristic that transmittance and reflectance are different.

A polarization detector that is equipped with a wire grating determined according to the wavelength of the light to be detected, and detects only polarized light whose electric vector direction is perpendicular to the direction of the wire grating by entering the semiconductor photodetector. be.

[Industrial application field]

The present invention relates to a polarization detector that detects polarized light having a specific polarization direction.

[Conventional technology]

BACKGROUND ART Conventionally, there has been a demand for a polarization detector that detects polarized light having a specific polarization direction, but there has been no simple means to meet this demand.

[Problem that the invention seeks to solve]

Conventionally used polarization detectors have a structure that combines an analyzer and a light receiving device, and must be assembled with the optical axes of the light source, analyzer, and semiconductor light receiving device aligned, making them difficult to handle. Therefore, it has been desired to develop a polarization detector that has an integrated structure and is easy to handle.

[Means for solving problems]

As shown in FIG. 1, in the present invention, a wire grating (a plurality of mutually parallel non-transparent strips) 3 is provided on the light receiving surface 2 of a semiconductor light receiving device 1, and the pitch of the wire grating 3 is is set to be less than or equal to the wavelength of the detected light, and the width of each non-transparent strip forming the wire grating 3 is set to be 60% or more of the above-mentioned pitch.

[Effect]

J, P, Auton (Appl, Opt,
6 10 198? ), a wire lattice has the characteristic of transmitting a large amount of light having an electric vector perpendicular to the wire and reflecting a large amount of light having an electric vector parallel to the wire, for light having a wavelength longer than the lattice spacing. Then, let the transmittance of the former be T and the transmittance of the latter T be v
If p, respectively, where Z Z is the equivalent impedance of the wire grating for the components of the electric vector v′p of light whose direction is perpendicular and parallel to the wire, respectively, and n is the wire grating provided above it. It is the refractive index of the material of the calendar.

Using the above formula to find the conditions under which both the extinction ratio and the transmittance (TV) are approximately 60%, we find that D/2, a>0. θD is obtained.

however, The extinction ratio is (T - T)/(TV + T,) and p can be.

D is the pitch of the wire grid; a is the width of the wire.

Therefore, as shown in FIG.
If a wire grating (a plurality of mutually parallel non-transparent strips) 3 that satisfies the above conditions is provided on the light receiving surface 2 of the wire grating 3, polarized light in the direction parallel to the wire grating 3 will be blocked, Only the polarized light in the direction perpendicular to the direction of the grating 3 enters the semiconductor photodetector, which functions as a polarization detector.

〔Example〕

Hereinafter, a polarization detector using a germanium avalanche photodiode according to an embodiment of the present invention will be further described with reference to the drawings.

Referring to FIG. 2, a germanium avalanche photodiode 1 is manufactured using a known method. That is, a p-type region 5 having a thickness of about 0.47 Lm and a diameter of about 200 to 400 ILm is formed in a part of the surface layer of the n-type germanium substrate 4 to serve as a light-receiving layer, and this p-type region (Light-receiving layer)
5, a deep ring-shaped p-type steel region 6 is formed to serve as a guard ring, and surrounding the guard ring 6 and at some distance from it, an n-type region 7 is formed to serve as a channel stopper; A silicon dioxide layer 8 is formed on the surface layer, and is used as an anti-reflection coating film on the light-receiving layer 5, and as a field insulating film in the surrounding area.

In a partial region (generally surrounding area) on the light-receiving layer 5, the silicon dioxide layer 8 is removed to form Au/Zn/Au.
(100/60/340 people) + Cr/ Au (300/
A negative electrode 9 is formed by stacking 1.50 OA), and a positive electrode 10 made of AuGe or the like having a thickness of about 2,000 OA is formed on the lower surface of the substrate 4. As a result, the diameter of the light receiving part is 1
It will be about 00-300JL11.

Refer to FIG. 3 Next, a wire grating is formed on the anti-reflection coating film 8 forming the light receiving surface.

The absorption wavelength of germanium photodetector is approximately 1 + 300
Since n ta, if we calculate the above conditions based on this wavelength, the pitch of the wire grid is about 2,500 people,
The width of the wire will be approximately 1,750 people.

A wire grating that satisfies this condition is manufactured using a two-beam interferometry method using light with a wavelength of 3,250^ emitted by a helium cadmium laser.

That is, a layer 11 of Cr/Au, which is the material of the wire grid.
After forming a photoresist film 12 on the light receiving surface to a thickness of about 300/1,500^, a photoresist film 12 is formed on the light receiving surface.

Refer to Figure 4. Based on Equation 1, which shows the principle of two-beam interferometry, -i ゝθ=s+n (1), θ=40' is determined, and θ is set at an angle of 40° to the light-receiving surface.
3,250 people were illuminated from an angle of 2.
Form interference fringes of 50 OA, expose and develop so that the pitch is 2,500 and the width of the exposed area or non-exposed area is about 1,750^ to form an etching mask of 12° with the above dimensions. Then, using this etching mask 12°, the Cr/Au layer 11 is etched to form the wire grid 3.
form.

When light with a wavelength of 1.300 nm is incident on the polarization detection device manufactured by the above process, about 90% of the polarized light in the direction parallel to the wire grating will be reflected, while the polarized light in the direction perpendicular to the wire grating will be reflected. Since about 60% of the polarized light is transmitted, only this transmitted polarized light reaches the semiconductor light receiving device, and only this polarized light can be detected.

〔Effect of the invention〕

As explained above, according to the present invention, a wire grating is formed on the light receiving surface of a normal semiconductor light receiving device, and the pitch of the wire grating is selected to be smaller than 1/2 of the wavelength of the detected light. , so the width of the wire grating is chosen to be greater than 60% of the pitch.

Only the polarized light in the direction perpendicular to the wire grating is detected by the semiconductor light receiving device, making it possible to provide a polarized light detector that has an integrated structure and is easy to handle.

[Brief explanation of the drawing]

FIG. 1 is a conceptual configuration diagram of a polarization detector according to the present invention. 2 to 4 are cross-sectional views of a substrate after completion of the main steps for manufacturing a polarization detector according to an embodiment of the present invention. l...Semiconductor light receiving device, 2... Light receiving surface. 3. Fist/wire lattice (multiple non-transparent strips parallel to each other), 4... H-type germanium substrate, 5... P-type layer (light-receiving layer), 6... P-type layer (guard ring),
7... N-type layer (channel stopper), 8. Kensha silicon dioxide layer (non-reflective coating film, field insulating film), 9. φ. negative electrode, 10.. positive electrode, 11.
...Cr/Au layer, 12...Photoresist film, Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] A semiconductor light-receiving device (1) has a plurality of mutually parallel non-light-transmitting strips (wire gratings) (3) provided on the light-receiving surface (2) of the semiconductor light-receiving device (1); Multiple non-transparent strips (wire grid) (3
) The pitch between the non-transparent strips constituting the plurality of non-transparent strips (wire gratings) (3) that are parallel to each other is smaller than 1/2 of the wavelength of the detected light. A polarization detector characterized in that the width of each of the light-transmitting strips is greater than 60% of the pitch.