JPS6193671A - light detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photodetection device disposed, for example, at the light transmission end of an optical fiber, and particularly to the configuration of its light receiving section.

In an optical communication device, the light detection device that converts an optical signal into an electrical signal is disposed at the light transmission end of the optical fiber.

In this photodetecting device, even if there is a slight deviation in the coupling angle of the light-receiving part surface with respect to the axis of the optical fiber, the sensitivity of the conversion is small (but the light-receiving part that enters the optical fiber It is desirable that there is less light reflected from the surface.

[Conventional technology]

Figure 5 shows M, which is a photodetector coupled to an optical fiber.
SM-PD (Metal Sem1 conductor
r Metal Photo.

FIG. 6 is a side sectional view showing the conventional structure of the light receiving section.

In both figures, 1 is a substrate made of, for example, gallium arsenide (GaAs), 2 is an active layer made of the same material as substrate 1 and made, for example, of n-type, and 3 and 4 are made of, for example, titanium-platinum-gold (Ti-Pt).
-Au), etc., forming a pair of electrodes in a comb shape, and 5 is a light receiving portion formed by meshing the comb teeth of electrodes 3 and 4.

The comb teeth of electrodes 3 and 4 are approximately 3 μm wide and approximately 100 μm long.
The distance between the electrodes 3 and 4 is about 3 μm, and the size of the light receiving part 5 is about 1 μm, which matches the thickness of the optical fiber 6, which is about φ0.1 fl.
It is 00 μm square.

When coupled to an optical fiber, this photodetecting device is arranged with the surface of the light receiving section 5 facing the end surface 6a of the optical fiber 6 as shown in FIG. Convert to electrical output.

That is, when a voltage is applied between the electrodes 3 and 4, a depletion layer is also formed between the electrodes 3 and 4 in the active layer 2, and electrons and holes are generated in the depletion layer by the incidence of light. current flows.

The sensitivity of the output to the incident light reaches its maximum value when the direction of the incident light (arrow shown in FIG. 6) is perpendicular to the surface of the light receiving section 5. That is, in the case of coupling with the optical fiber 6, the coupling angle θ (shown in FIG. 7) between the surface of the light receiving section 5 and the central axis 6b of the optical fiber 6 reaches its maximum value when it is 90 degrees.

[Problem that the invention seeks to solve]

However, when the configuration of the light receiving section 5 is as shown in FIG. 6, the sensitivity changes largely with respect to the coupling angle θ, as shown by the curve a in FIG. The bond angle .theta. must be made accurate when installing, which poses a problem of lowering the yield due to this arrangement.

Although it is desired that the amount of reflected light from the light receiving section 5 that enters the optical fiber 6 be small, since the light that enters the light receiving section 5 is reflected approximately perpendicularly, the reflected light directly hits the end surface 6a. Although it is possible to reduce the amount of reflected light hitting the end face 6a by coating the surface with a normal anti-reflection film (not shown), it still hits the end face 6a.

[Means for solving problems]

The above problems are solved by the photodetection device of the present invention, in which a film with a convex lens structure is formed on the light receiving portion surface.

[Effect]

Since the incident light is focused on the active layer by the film of the lens structure, even if the coupling angle between the light receiving surface and the central axis of the optical fiber deviates from 90 degrees, the sensitivity will not decrease from the maximum value. This is smaller than in the past, making it possible to prevent a reduction in yield due to the arrangement of the photodetector.

Further, the reflected light from the film diverges, and the amount of light directly hitting the end face of the optical fiber is reduced, thereby reducing the amount of light that enters the optical fiber.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals refer to the same objects throughout the design.

FIG. 1 is a side sectional view showing the configuration of an embodiment of the light receiving section of a photodetector according to the present invention, FIG. 2 is a characteristic diagram showing the effect of the present invention on sensitivity characteristics with respect to the coupling angle with an optical fiber, and FIG. , and FIG. 4 are side sectional views showing the configuration of other embodiments of the light receiving section of the photodetector according to the present invention.

FIG. 1 is a diagram corresponding to FIG. 6, and the light receiving section shown in FIG. 1 has a lens film 7 added to the conventional light receiving section shown in FIG.

That is, the lens film 7 is formed by patterning a resin transparent to incident light, such as an AZ resist, to form the electrodes 3 and 4.
For example, 240 to 3
The resin was shaped into a convex lens shape by heating at 00°C.

Since the incident light is focused on the active layer 2 by this lens film 7, the sensitivity characteristic with respect to the bond angle θ in FIG.
The curve becomes as shown in the figure, and the reduction in sensitivity from the maximum value when the coupling angle θ deviates from 90 degrees is smaller than that of the conventional method shown in curve a. This makes it possible to prevent a reduction in yield due to installation.

Further, the reflected light from the lens film 7 becomes divergent, and the amount of light directly hitting the end face 6a of the optical fiber halo is reduced, thereby reducing the amount of light that enters the optical fiber halo.

In the embodiment shown in FIG. 3, the added lens film is a single lens film 7a that covers substantially the entire surface of the light receiving section 5. This lens film 7a can be formed by depositing the resin on substantially the entire surface of the light receiving section 5 by the patterning.

The operation is substantially the same as that shown in FIG.

The embodiment shown in FIG. 4 is obtained by adding an antireflection film 8 to the embodiment shown in FIG. An antireflection coating 8 covers the lens membrane 7 and the electrodes 3.4.

The effect of this embodiment is that, in addition to the effect of the case shown in FIG. 1, the incident light at the edges of the electrodes 3 and 4 can also be focused on the active layer 2, and the effect of a normal antireflection film is also superimposed. , which is better than the case shown in FIG. As the material of the antireflection film 8, a resin having a refractive index different from that of the material of the lens film 7 may be used.

The reason why resin was used as the material for the lens crotch 7 was to avoid high-temperature treatment in the manufacturing process since the active layer 2 of the photodetector shown in the example is made of GaAs.
The material is not limited to resin, for example, AZ resist, as long as it satisfies the conditions of not degrading the materials such as 2. The same applies to the antireflection film 8.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, even if the coupling angle between the light-receiving part surface and the central axis of the optical fiber deviates from a predetermined angle, the decrease in sensitivity from the maximum value is smaller than before.
In addition, it is possible to provide a photodetection device in which the direction of reflected light diverges, making it possible to prevent a decrease in yield when disposed at the end of the optical fiber and to reduce reflected light incident on the optical fiber. effective.

[Brief explanation of drawings]

In the drawings, FIG. 1 is a side cross-sectional view showing the configuration of an embodiment of the light receiving section of the photodetector according to the present invention, and FIG. 2 is a characteristic diagram showing the effect of the present invention on sensitivity characteristics with respect to the coupling angle with the optical fiber. 3 and 4 are side sectional views showing the configuration of other embodiments of the light receiving section of the photodetector according to the present invention, FIG. 5 is a perspective view of an example of the photodetector coupled to an optical fiber, and FIG. 6 7 is a side sectional view showing the conventional configuration of the light receiving section.
The figure is a side view showing the coupling with the optical fiber. In the figure, ■ is the substrate, 2 is the active layer, 3.4 is the electrode,
5 is the light receiving part, 6 is the optical fiber, 6a is the end of 6, 6b is the central axis of 6, 7.7a is the lens back, 8 is the antireflection film,
θ represents a bond angle, a represents a conventional characteristic, and b represents a characteristic of the present invention. stomach. 4. Gi 2 Mintei Otsug

Claims (1)

[Claims] A photodetecting device characterized in that a film having a convex lens structure is formed on a light receiving portion surface.