JPH01241032A - Optical output monitoring device - Google Patents

Abstract

PURPOSE:To cause the title device to cope with a laser chip assembled by a junction-down system while occurrence of cross talks is prevented by forming light condensing grating couplers which lead monitor light to waveguides and, at the same time, light receiving elements at the positions to which each monitor is condensed. CONSTITUTION:Waveguides which propagate monitor light in the monitor light projecting direction on a substrate are provided and light condensing grating couplers 7 which lead the monitor light to the waveguides are formed on the waveguides. At the same time, light receiving elements 4 are formed in such a state where the elements 4 are respectively brought into contact with the waveguides at the positions to which each monitor light refracted by each grating coupler is condensed. Therefore, the junction-down system can be coped with this device and, as a result, deterioration of the performance of the light receiving elements 4 can be prevented because heat is easily diffused into the substrate. Thus the reliability of the light emitting device can be improved and occurrence of cross talks between the laser light and adjacent monitor light can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention focuses monitor light having an optical output corresponding to the optical output of the irradiated light irradiated onto an irradiated object onto a light-receiving element. The present invention relates to a light output monitor device that detects light output.

Disaster■ KogyokuIn recent years, as optical disk devices have become more sophisticated and multifunctional,
Demand for multibeam semiconductor lasers is increasing. In the multi-beam semiconductor laser, it is necessary to independently control each beam output, and for this purpose, it is necessary to independently monitor each optical output. However, in the conventional multi-beam semiconductor laser optical output monitor device, the fourth
As shown in the figure, since the interval between the light emitting points 32 of the monitor light 330 emitted from the semiconductor laser 31 is narrow, typically 100 μm, crosstalk occurs between the monitor light 33 and the adjacent monitor light 33 . For this reason, there was a problem in that the light receiving element 37 could not accurately measure the amount of irradiation light 38 corresponding to each monitor light 33. Therefore, as shown in FIG. 5, it has been proposed to use separators 34 that bend the optical axis of the monitor light 33 at both ends approximately at right angles. With such a structure, it is possible to prevent crosstalk from occurring between adjacent monitor lights 33, so that the light intensity of each irradiation light 38 can be accurately measured by the light receiving element 37.

By the way, when a monolithic multi-beam semiconductor laser is used as described above, it is generally known that as the number of beams increases, the device performance deteriorates due to thermal interaction. In particular, when the laser chip 31 is assembled using the junction-up method as shown in FIG. , the device performance deteriorates significantly, υ1°.Therefore, in order to prevent the device performance from deteriorating, it is desirable to assemble the laser chip by the junction-down method, as shown in FIG. 6(b).

O<”°I will do it.

However, in the conventional structure described above, it is difficult to make the reflective surface near the submount 36 a perfect mirror surface because the edges of the separator 34 curl up during processing. Submount 36 to
It is difficult to install it at right angles. Therefore, the optical axis 35 of the monitor light 33 of the laser chip 31 is aligned with the submount 3.
If the laser chip is assembled using a junction-down method where the laser chip is located close to the surface of 3, the monitor light 3
3 is incident on the submount 36 and a part of it is absorbed by the submount 36. As a result, the amount of the monitor light 33 cannot be measured accurately, making it difficult to measure the laser output.

The present invention has been made in consideration of the above-mentioned conventional problems, and an object of the present invention is to provide an optical output monitor device that can prevent crosstalk from occurring and is compatible with laser chips assembled using the junction-down method. It is something to do.

In order to achieve the above object, the present invention is provided on a substrate and has a plurality of irradiation lights that irradiate an object to be irradiated and a light output corresponding to each of the light outputs of the irradiation light. In an optical output monitoring device comprising a semiconductor laser that emits monitor light and a plurality of light receiving elements that individually detect the plurality of monitor lights, a waveguide for propagating the monitor light in the direction of irradiation of the monitor light on the substrate is provided. A condensing grating coupler is formed on the waveguide to guide the monitor light to the waveguide, and the light receiving element is placed in contact with the waveguide at a condensing position of each monitor light refracted by the condensing grating coupler. It is characterized by the fact that it has been formed.

In the above configuration, a waveguide for propagating the monitor light is provided on the substrate on which the semiconductor laser is provided, and a grating coupler for guiding the monitor light to the waveguide is formed on the waveguide. Therefore, it becomes possible to support a junction down method in which the distance between the light emitting point and the substrate is short. Therefore, since heat is sufficiently diffused into the substrate, deterioration of device performance can be prevented.

Furthermore, since the distance between adjacent light emitting points of a multi-beam semiconductor laser is usually 100 μm or more, even if adjacent monitor lights are incident on the condensing grating coupler, this monitor light will The light is not focused on the light receiving element corresponding to the light collecting grating coupler. Therefore, it is possible to prevent crosstalk from occurring between adjacent monitor lights.

First Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

A laser chip 2 assembled by a junction down method is fixed to one end of a submount 1 made of n-type silicon. This laser chip 2 is an irradiation light 1 that irradiates an object to be irradiated such as a compact disk (not shown).
0 and three monitor lights 11 emitted from the opposite side to the irradiation light and having a light output corresponding to the light output of the irradiation light. On the surface of the submount 1 on the side irradiated with the monitor light 11, there is a SiO□ buffer N3 made by thermally oxidizing the n-type silicon.
The SiO□ buffer layer 3 is composed of an upstream buffer layer 3a and a downstream buffer layer 3b. The submount 1 between the upstream buffer layer 3a and the downstream buffer layer 3b (the condensing position of each monitor light refracted by the condensing grating coupler 7 described later) includes:
A light receiving element 4 is formed of p-type silicon produced by thermally diffusing n-type silicon.

Further, on the downstream buffer IJab, an electrode 5 having an area that can be wire bonded is formed by vapor deposition or the like, and this electrode 5 is connected to the light receiving element 4 and the lead 8.
connected by. A Corning 70594 wave N6 is formed on the surface of the lead 8, the surface of the light receiving element 4, and the surface of the upstream buffer layer 3a by sputtering or the like, and the laser beam on the Corning 7059 waveguide layer 6 Three condensing grating couplers (hereinafter referred to as FCC) 7 are arranged in parallel on the chip 2 side. These FGCs 7 have a function of refracting the three corresponding monitor lights 11, coupling them to the Corning 70591 wave layer 6, and focusing the monitor lights 11 on each light receiving element 4 individually. .

In the above configuration, the optical output monitoring device of the present invention is operated as follows.

The laser chip 2 emits irradiation light 10 that irradiates an object to be irradiated, and monitor light 11 having an optical output corresponding to the optical output of this irradiation light IO. A part of this monitor light 11 is incident on the FGC 7 formed corresponding to each laser beam emission point 13, is refracted, and is combined in the waveguide layer 6. Thereafter, the monitor light 11 propagates within the waveguide layer 6 by the light focusing function of the FGC 7 and is focused on the light receiving element 4 corresponding to each monitor light 11.

By the way, the coupling efficiency of the laser beam to the waveguide layer 6 by the FGC 7 strongly depends on the positional relationship between the FGC 7 and the laser beam emission point 13, and if this positional relationship deviates significantly from the designed value, the coupling efficiency will decrease. is known to decrease dramatically. In the above case, the distance between adjacent light emitting points 13 of the laser chip 2 is usually 100 μm or more in consideration of deterioration of device performance due to thermal interaction, so that the adjacent monitor light 11 is Even if the monitor light is incident on the FGC 7, this monitor light is not focused on the light receiving element 4 corresponding to the FGC 7.

As a result, only the corresponding monitor light 11 is focused on each light receiving element 4.

(Second Embodiment) A second embodiment of the present invention will be described below based on FIG. 3.

A grating lens 10 corresponding to each monitor light is formed between the FGC 7 and the light receiving element 4, and the optical axis of the monitor light 11 at both ends of the monitor light 11 emitted from the FGC 7 is tilted outward. The configuration is substantially the same as that of the first embodiment.

In this way, the distance between the light receiving elements 4 can be made wider than the distance between the light emitting points 13, so the area of each light receiving element 4 can be made larger than in the first embodiment. Therefore, the same effects as in the first embodiment can be achieved, and the optical output monitoring device can also be manufactured easily.

It goes without saying that even if the FGCT itself has a function of tilting the optical axis of the monitor light, the same effect as described above can be achieved.

Furthermore, in the first and second embodiments, three monitor lights 11 are emitted from the laser chip 2, but the structure is not limited to this, and two monitor lights 11 are emitted from the laser chip 2. Light 11 or 4 or more monitor lights 1
Even when 1 is issued, the same effects as in both of the above embodiments are achieved.

As described above, according to the present invention, it becomes possible to support the junction down method, so that heat can be easily diffused into the substrate, and deterioration of element performance can be prevented. Thereby, the reliability of the light emitting device can be significantly improved.

Furthermore, since it is possible to prevent crosstalk from occurring between adjacent monitor lights, it is possible to dramatically improve the detection accuracy of the light output monitor device.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the propagation path of monitor light in the optical output monitoring device of the first embodiment, FIG. 2 is a side view of the optical output monitoring device of the first embodiment, and FIG. 3 is a plan view of the optical output monitoring device of the second embodiment. FIG. 4 and FIG. 5 are schematic explanatory diagrams showing a conventional optical output monitoring device, and FIG. 6 is a side view showing a method for assembling a semiconductor laser. . 1...Submount, 2...Laser chip, 4...
- Light receiving element, 6... Corning 7059 waveguide layer, 7.
...Concentrating grating coupler.

Claims (1)

[Claims] (1) A semiconductor laser that is provided on a substrate and emits a plurality of irradiation lights that are irradiated onto an object to be irradiated and a monitor light that has an optical output corresponding to each of the light outputs of the irradiation light, and a semiconductor laser that emits monitor light that has an optical output corresponding to each of the light outputs of the irradiation light, and the plurality of monitor lights that are individually transmitted. In an optical output monitoring device equipped with a plurality of light receiving elements for detecting the An optical output monitoring device characterized in that an optical grating coupler is formed, and the light receiving element is formed so as to be in contact with the waveguide at a condensing position of each monitor light refracted by the condensing grating coupler.