JPH05121841A - Semiconductor laser module - Google Patents

Abstract

PURPOSE:To provide a low-cost general-purpose and volume-sales semiconductor laser module suitable in a branch-line/subscriber's line optical communication system market. CONSTITUTION:A semiconductor laser device 1 is mounted on a stem 3 and is airtightly sealed with a thick-wall cap 4a having a microlens 5. A fiber ferrule 8 is inserted in a spherical lens holding tube 6a for holding an inner spherical lens 7. The tube 6a and the ferrule 8 are adjusted in X-Y directions and Z direction so that the overall location is fixed by a spot welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser module coupled with an optical fiber, and more particularly to a semiconductor laser module suitable for a single mode optical fiber and used for branch line and subscriber optical communication.

[0002]

2. Description of the Related Art A semiconductor laser device used for optical communication must be efficiently coupled with an optical fiber. In recent years, single-mode fibers have become popular, and single-mode fibers have come to be used even in the branch line / subscriber system. Therefore, even in the semiconductor laser module used for this purpose, the self-cleaning Such a gradient index rod lens capable of highly efficient coupling is used as a coupling lens.

FIG. 3 is a sectional view of a semiconductor laser module using a gradient index rod lens. As shown in the figure, the semiconductor laser device 1 is mounted on the stem 3 via a heat sink 2 and hermetically sealed by a thin cap 4c. The lens holder 12 holding the rod lens 13 is fixed to the stem 3 by spot welding, and the ferrule holder 14 holding the fiber ferrule 8 is fixed to the lens holder 12 by spot welding. In FIG. 3, 9 spot welds
Is indicated by a black circle.

The light emitted from the semiconductor laser device 1 is
The light is taken out of the can case through the window glass of the cap 4c, condensed by the rod lens 13, and incident on the end face of the optical fiber held by the fiber ferrule 8.

As shown here, the can case mounting type semiconductor laser module is a so-called coaxial type module in which the shape and arrangement method of the members are axially symmetric, and in this structure, an electronic cooling element and a drive circuit are provided. Since it is difficult to combine modules including peripheral elements such as, a module of this shape is manufactured for the so-called branch / subscriber general-purpose mass-market.

[0006]

Although the above-mentioned semiconductor laser module is intended for a general-purpose mass-market, it has a large number of parts and uses a rod lens, so that it is difficult to reduce the cost. Usually, the gradient index rod lens is manufactured at a high price because it is manufactured through a process requiring complicated and strict control such as diffusing impurities into a glass rod as a base material by an ion exchange method. I have no choice. Therefore, in the conventional semiconductor laser module, the cost of the mounting member exceeds the cost of the mounting pellet, which is relatively expensive as a general-purpose product. In view of this point, an object of the present invention is to realize cost reduction of a module in response to a demand in a general-purpose mass sales market without deteriorating characteristics such as coupling efficiency.

[0007]

A semiconductor laser module according to the present invention has a stem serving as a base of a can case, a semiconductor laser element mounted on the stem, and a transmission window through which laser light is transmitted. A thick-walled cap that seals the semiconductor element on the stem; a spherical lens inside; a metal tube that holds a fiber ferrule at one end and the other end is fixed to the cap; To do.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention. In the figure, 1 is a semiconductor laser device, 2 is a heat sink, 3 is a stem, 4a is a can case together with the stem 3, and a thick cap that hermetically seals the semiconductor laser device 1 is provided. 5 is an opening of the cap 4a. 6a is a spherical lens holding barrel for holding the spherical lens 7, 8 is a fiber ferrule inserted and fixed in the barrel 6a, and 9 is a spot weld.

In the coaxial type module, the thickness of the cap is usually about 120 μm, but in this embodiment,
Since the cap also serves as a structural material that supports the lens barrel 6a, the spherical lens 7, and the fiber ferrule 8 as a whole,
The wall thickness is set to be as thick as 500 μm.

The curvature of the microlens formed in the opening of the cap is determined by the surface tension and the weight of the glass material. The laser light emitted from the semiconductor laser device 1 is
It is converted into a parallel beam by the microlens 5.

To assemble this module, after aligning the semiconductor laser element 1 and the microlens,
The cap 4a is fixed to the stem 3 to seal the laser element. Next, the fiber ferrule 8 is inserted into the lens barrel 6a containing the spherical lens 7, the lens barrel 6a is placed on the thick cap 4a, and the X and Y axis adjustment is performed between the lens barrel 6a and the thick cap 4a. The Z-axis is adjusted between the cylinder 5 and the ferrule 6, and each member is fixed by YAG laser spot welding at the optimum position for optical coupling. At this time, since the outer diameter of the ferrule is not substantially equal to the inner diameter of the lens barrel, the adjustment can be easily performed.

The microlens simply drops molten glass,
It can be formed only by solidifying, and a spherical lens can be formed by polishing a large number of materials cut from a uniform glass material into a spherical shape at a time, so it is much cheaper than a rod lens. Can be manufactured.

In the present embodiment, these inexpensive lens systems were adopted in place of the rod lens which was the mainstream in the past, and a module having a coupling efficiency of -7 to -10 dB could be realized. Further, by using a thick cap and supporting the optical system, the number of members can be suppressed and the module can be provided at a lower cost.

FIG. 2 is a sectional view showing a second embodiment of the present invention. The difference of this embodiment from the previous embodiment is that, instead of the microlens, a lens holding plate 11 holding the spherical lens 10 is attached so as to cover the opening of the thick cap 4b, and this holding plate 11 is attached. Ball lens holding barrel 6
This is the point where b is fixed.

To assemble the module of this embodiment, the ball lens holding plate 11 holding the ball lens 10 is fixed to the lens barrel 6b holding the ball lens 7, and the fiber ferrule 6 is inserted into the lens barrel 6b. This assembly is placed on a can case, the ball lens holding plate 11 is moved in the X and Y axis directions, and the fiber ferrule is moved in the Z axis direction, and spot welding is performed at the best optical coupling position. The present embodiment has an advantage that the optical adjustment only needs to be performed once, as compared with the previous embodiments.

[0016]

As described above, according to the semiconductor laser module of the present invention, the can case has a thick cap, and the lens barrel holding the spherical lens and the fiber ferrule is fixed to the can case. According to the invention,
Since the number of parts can be reduced and necessary coupling efficiency can be realized without using a rod lens, a module for single mode optical fiber can be provided at low cost for general-purpose mass sales. In addition, since the fiber ferrule can be optically adjusted while being held in the lens barrel, and the fixing can be performed by laser spot welding or the like, position adjustment and fixing work can be easily performed. Like

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

 1 Semiconductor Laser Element 2 Heat Sink 3 Stem 4a, 4b Thick Cap 4c Thin Cap 5 Micro Lens 6a, 6b Ball Lens Holding Lens Tube 7, 10 Ball Lens 8 Fiber Ferrule 9 Spot Welding Part 11 Ball Lens Support Plate 12 Lens Holder 13 Rod Lens 14 Ferrule holder

Claims (1)

[Claims] 1. A stem serving as a base of a can case,
A semiconductor laser element mounted on the stem, a transmission window through which laser light is transmitted, a thick cap for sealing the semiconductor laser element on the stem, a spherical lens inside, and one end A semiconductor laser module, comprising: a metal tube having a fiber ferrule held in a portion thereof and the other end thereof fixed to the cap.