JPH0447980Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to an optical monitor for monitoring laser light, etc.

(b) Prior art At present, optical disk reading devices use three independent resonators arranged in parallel at intervals of about 100 μm so that each beam for erasing, reading, and writing can be output individually. A three-beam type semiconductor laser has been proposed (Utility Application No. 61-40952).

In order to independently monitor the laser beams emitted from adjacent resonators, Japanese Patent Laid-Open No. 58-
As disclosed in Japanese Patent No. 102590, a method of arranging a monitoring light receiving element for each resonator near the resonator can be considered.

Figure 4 schematically shows such a method.
-3 are semiconductor laser chips, and the distance between the optical axes 4 of the laser beams output from each chip is
They are arranged so that the distance is 100 μm. Also,
Laser light 1a output from each of the above chips 1 to 3
The beam spread angle θ of ~3a is 10°. 5-7
are light-receiving elements, and the light-receiving elements are arranged to face the chips 1 to 3, respectively.

(c) Problems to be solved by the invention However, as is clear from FIG.
If it is 500 μm or more, each laser beam will be superimposed on the light receiving element side. Therefore, each light receiving element 5~
7 also receive laser light output from chips other than the laser chips facing each other,
It becomes impossible to monitor each individual laser chip.

Note that the above problem can be solved by setting the distance between each chip 1 to 3 and the light receiving elements 5 to 7 to 500 μm or less, but
Providing the laser chip and the light receiving element in close proximity to each other in this manner complicates optical axis alignment between the laser chip and the light receiving element, wiring by wire bonding, etc., and is not practical.

Furthermore, as a method to solve the above-mentioned problem, it is possible to optically couple the associated semiconductor laser chip and the light-receiving element with an optical fiber so that the distance between the laser chip and the light-receiving element is set to the required size. This method has a problem in that the device becomes larger due to the attachment of the optical fiber.

(d) Means for solving the problems The present invention has been made in view of the above points, and its structural features include a semiconductor substrate of one conductivity type, and one conductivity type of the substrate.
a light-receiving region selectively formed on the main surface; a buffer layer laminated on one main surface of the substrate excluding at least the surface of the light-receiving region; A waveguide made of a material having a larger optical refractive index than the buffer layer is provided.

(E) Effect With such a configuration, the waveguide for propagating light and the light receiving element can be integrated in a small size.

(F) Embodiment Figures 1 and 2 show embodiments of the present invention.
12 is an n ⁺ type silicon substrate, and 12 is an n ^- type silicon layer, which is epitaxially grown on the substrate 11 described above. 13 to 15 are first to third light receiving regions, which can be formed by selectively diffusing P-type impurities such as boron from the surface of the silicon layer 12. Reference numeral 16 denotes a buffer layer made of silicon dioxide, and the buffer layer is connected to the light-receiving areas 13 to 16.
It is laminated on the silicon layer 12 except for the surface 15 by, for example, a sputtering method. Note that the buffer layer 16
The boundary portion between each of the light receiving elements 13 to 15 is tapered.

17 to 19 are the first to third parts made of aluminum.
The electrodes are arranged on the right side of the buffer layer 16 and are arranged in the first to third light receiving regions 13 to 13, respectively.
15. 20 is a back electrode formed on the back surface of the substrate.

Reference numerals 21 to 23 are the first to third waveguides in the shape of a ridge made of glass material #7059 manufactured by Corning, Inc., for example. One end of the waveguide is aligned with the left end of the buffer layer 16 at a pitch of 100 μm, and the other end is aligned with the left end of the buffer layer 16 at a pitch of 100 μm. are laminated on the buffer layer 16 using sputtering and etching methods so as to be superimposed on the surfaces of the first to third light receiving elements 13 to 15, respectively.

In such a configuration, the optical refractive index of the waveguides 21 to 23 is approximately 1.54, the optical refractive index of the buffer layer 16 is approximately 1.46, the optical refractive index of air is approximately 1.0, and the refractive index around the waveguides 21 to 23 is approximately the same as that of the waveguide. It is smaller than that of 21-23. Therefore, for example, light incident from the left end of the waveguide 22 passes through the waveguide 22 as shown by the arrow in FIG. The light will be incident on the light receiving area 14 which is as large as 3.45. The tapered portion 22a is formed along the tapered portion of the surface of the buffer layer 16, and therefore, when the buffer layer 16 is not tapered, the tapered portion 22a of the waveguide 22 is not formed either. Moreover, when such a taper part 22a is not formed, the light receiving area 14 of the light propagating through the waveguide 22
Since the reflectance to the side decreases, the amount of light incident on the light receiving area 14 decreases.

Therefore, if a semiconductor laser chip is placed near the left end of each of the first to third waveguides 21 to 23, and the laser light output from the chip is made to enter the corresponding waveguide 21 to 23, the The incident laser light propagates through each of the waveguides 21 to 23 and is guided to the first to third light receiving regions 13 to 15.

In this embodiment, the waveguide is of a rigid type, but as shown in FIG.
6 are laminated on the entire surface and the first to third waveguides 21 to
A metal-loaded type may be used in which the metal 25 is laminated on the material layer 24 except for the portion 23.

(g) Effects of the invention Since the optical monitor of the invention integrates a waveguide and a light receiving element, the laser chip and the light receiving element can be optically coupled by simply aligning the waveguide and the semiconductor laser chip optically. and the structure for such coupling does not become large.

Moreover, since the waveguide and the light receiving region can be aligned with high precision using integration technology, the area of the light receiving region can be considerably reduced. Furthermore, as the area of the light-receiving region becomes smaller, its junction capacitance becomes smaller, so its response speed becomes faster, making it possible to monitor rapid fluctuations in laser output.

[Brief explanation of the drawing]

1 and 2 are perspective views and sectional views showing the first embodiment of the present invention, FIG. 3 is a perspective view showing the second embodiment of the invention, and FIG. 4 is a schematic diagram showing the conventional structure. It is. 11...n ⁺ type silicon substrate, 12... n ^- type silicon layer, 13-15... first to third light receiving regions,
16... Batsuhua layer, 21-23... 1st to 3rd
waveguide.

Claims (1)

[Scope of utility model registration request] a semiconductor substrate of one conductivity type; a light-receiving region selectively formed on one main surface of the substrate; a buffer layer laminated on one main surface of the substrate excluding at least the surface of the light-receiving region; a buffer layer laminated on the buffer layer; An optical monitor device comprising: a waveguide made of a material having a larger optical refractive index than the buffer layer and having one end optically coupled to the light receiving region.