JPH0621577A - Semiconductor laser module - Google Patents

Abstract

PURPOSE:To ensure a monitor current sufficient to APC control, even when the backward light output of a semiconductor laser element is small. CONSTITUTION:A carrier 42 mounting a photodiode element 2 is directly fixed to a carrier 41 mounting a semiconductor laser element 1. Hence the semiconductor laser element 1 is adjusted and fixed to a position where the maximum monitor current flows to the light receiving surface of the photodiode element 2, while observing the position with a TV camera or the like. Thereby the influence of dimensional precision of part members can be evaded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a semiconductor laser module equipped with a semiconductor laser device.

[0002]

It has been a long time since a semiconductor laser has been put into practical use as a light source for optical fiber communication. DIP (dualin
-Line package) type 14-pin box module with a built-in Pelje element for temperature control, and box or coaxial module without a Pelje element are currently available from the initial stage of commercialization. It is widely used up to. Generally, in these, the semiconductor laser device is so-called APC (Automatic Power) so as to keep the fiber input light output constant.
er Control: constant output control). Therefore, the optical output from the cavity end face opposite to the face optically coupled to the optical fiber of the semiconductor laser device is coupled to the photodiode device for monitoring, and the photocurrent is used as a control signal. I am using.

[0003]

The initial semiconductor laser device had the simplest structure of a Fabry-Perot resonator composed of a crystal-exposed reflecting surface, and therefore, an optical output of the same intensity was obtained from both end surfaces. Was given. However, after that, a dielectric thin film was formed on the end face of the resonator for high temperature operation and high output, and as a result of increasing the optical output from the front that is coupled to the optical fiber, the optical output from the rear was increased. The output has decreased. Similar situations occur in single-axis mode lasers such as DFB lasers. Since the photodiode element for monitoring essentially has a dark current component, if the input light intensity from the semiconductor laser element decreases and the photocurrent decreases, the S / N ratio as a control signal deteriorates. In order to increase the photocurrent, there are methods such as increasing the light receiving area of the photodiode element and bringing the semiconductor laser element and the photodiode element as close as possible. However, in the former case, not only the cost factor of the photodiode element but also the response speed decrease due to the expansion of the light receiving area limits the feasible light receiving area to, for example, about a hundred and several tens of μm. On the other hand, for the latter, the limit is set by the assembly position accuracy of each element in the actual module structure.

FIG. 4 shows a configuration example of a conventional semiconductor laser module. The semiconductor laser device 1 and the photodiode device 2 are mounted on separate carriers 41 and 42, respectively, and fixed on a common substrate 5. This is a design resulting from the necessity of individually screening each of them in manufacturing. In this figure, the deviation amounts in the X and Y directions from the optimum positions of the semiconductor laser element and the photodiode element are
It is determined by the dimensional accuracy of the heat sink 3 and the carriers 41, 42 and the mounting accuracy of the semiconductor laser device 1 and the photodiode device 2 on the carrier. In particular, the deviation in the Y direction cannot be corrected by adjusting the positional relationship between the carriers. Moreover, when the semiconductor laser element is mounted on the heat sink 3 upside down, the original Gaussian beam has a strong and weak cycle every several degrees due to the reflection interference on the surface of the heat sink. Appears as a large drop in monitor current.

Due to the various factors described above, there is a problem that a semiconductor laser module equipped with a semiconductor laser device having a small rear light output cannot obtain a sufficiently large monitor current for APC operation.

[0006]

A semiconductor laser module of the present invention comprises at least a semiconductor laser element, a photodiode element, and an optical fiber, and a carrier on which the photodiode element is mounted carries the semiconductor laser element. It is characterized by being directly fixed to the carrier.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a partial structural view of a semiconductor laser module which is an embodiment of the present invention. The semiconductor laser device 1 is fused to the heat sink 2 and further fused to the carrier 41. On the other hand, the photodiode element 2 is fused to the carrier 42, and the carrier 42
Fused to 1. Since the semiconductor laser element and the photodiode element are often electrically insulated and used, a ceramic material is used for the portion 421 of the carrier 42 where the photodiode element is fused, and a metal material portion 422 brazed thereto is used. It is fused to the carrier 41 using solder.

FIG. 2 is a partial structural view of a semiconductor laser module according to the second embodiment of the present invention. In this example, a metal coating is formed on the ceramic material carrier 42 to which the photodiode element 2 is fused, and the carrier 41 is solder-fused at that portion, which has the advantage of simplifying the structure of the carrier 42. .

FIG. 3 is a partial structural view of a semiconductor laser module according to the third embodiment of the present invention. In this example, the metal material portion 422 brazed to the ceramic material 421
Are fixed to the carrier 41 by laser welding.
If there are several soldered parts such as those mentioned here, lower fusion temperature conditions must be set for each process, and the temperature control must also be performed fairly accurately in general. There is. For example, in the case of FIG. 4, the solder for fusing the semiconductor laser element and the heat sink is AuS.
n eutectic (80:20, melting point 280 ° C.), the solder that fuses the photodiode element to the carrier is AuSi eutectic (melting point 370 ° C.), and the solder that fuses the heat sink to the carrier is AuSn eutectic (10:90, The melting point is 217 ° C.), and the solder for fusing each carrier to the substrate can have a structure of PbSn eutectic (melting point 183 ° C.). In each fusing step, previously assembled parts are not re-melted. Therefore, it is necessary to accurately control the temperature.
When laser welding is used to fix the carriers to each other as in this embodiment, there are advantages that these restrictions can be relaxed and the degree of freedom in selecting the solder material used for other portions can be increased.

[0010]

In the semiconductor laser module constructed as in the above-mentioned embodiments, when fixing the carrier carrying the semiconductor laser element and the carrier carrying the photodiode element, the semiconductor laser module is coupled with the optical fiber of the semiconductor laser element. While observing the two in the Z-axis direction in the figure from the side that is being viewed, for example, with a TV camera, fix both with the beam emission position of the semiconductor laser device at the optimum position with respect to the light-receiving surface of the photodiode device. It becomes extremely easy to carry out, and the problem that the adjustment in the Y-axis direction cannot be performed is solved. As a result, it is possible to obtain a sufficient monitor current for performing the APC operation even when the semiconductor laser module is configured by using the semiconductor laser device having a small optical output from the rear.

[Brief description of drawings]

FIG. 1 is a partial configuration diagram of a semiconductor laser module that is an embodiment of the present invention.

FIG. 2 is a partial configuration diagram of a semiconductor laser module that is an embodiment of the present invention.

FIG. 3 is a structural partial view of a semiconductor laser module which is an embodiment of the present invention.

FIG. 4 is a partial structural view of a conventional semiconductor laser module.

[Explanation of symbols]

 1 Semiconductor Laser Element 2 Photodiode Element 3 Heat Sink 41 Carrier 42 Carrier 5 Substrate

Claims (1)

[Claims] 1. A semiconductor laser module including at least a semiconductor laser element, a photodiode element, and an optical fiber, wherein a carrier having the photodiode element mounted thereon is directly fixed to the carrier having the semiconductor laser element mounted thereon. A semiconductor laser module characterized in that