JPH03282506A - Semiconductor laser unit with optical fiber - Google Patents

Abstract

PURPOSE:To suppress a decrease in light output by covering the periphery of a semiconductor laser, which includes the terminal part of an optical fiber, with an optically transparent adhesive. CONSTITUTION:The semiconductor laser 30 is divided into a laser oscillation part 31 and a groove formation part 32. The oscillation part 31 is formed of a signale-axis mode laser which has a diffraction grating 33 provided nearby an active layer 34. At the groove formation part 32, a groove 36 for fixing the fiber terminal part 35 with which the output light from the oscillation part 31 is coupled is formed. The periphery of the terminal part 35 and oscillation part 31 is covered with the optically transparent adhesive 37 and the terminal part 35 is fixed to the groove 36 with the adhesive 37. Thus, the light output decrease can be suppressed small.

Description

[Detailed description of the invention] [Industrial usage total] The present invention relates to a semiconductor laser unit with an optical fiber.

[Conventional technology]

Conventionally, there are two types of optical coupling between a semiconductor laser and an optical fiber in a semiconductor laser unit with an optical fiber: one using a lens, and one directly coupling by processing the end face of the optical fiber. These conventional examples were reported at the Global Telecommunications Conference, I-Triple E, Atlanta, Georgia, USA in November 1984, and published in 1161 of the same journal.
Ni Doll (A, DO) listed on pages 1165 to 1165
He is familiar with papers such as LL).

Those that use lenses can have large tolerances for the optical system, but the distance between the semiconductor laser and the optical fiber is 1
It becomes 0- or more, and is not suitable for miniaturization. In this respect, the direct coupling method in which the end face of the optical fiber is processed is extremely advantageous for miniaturization.

The advantages of downsizing the optical system are as follows.

(b) There is more space for mounting, making it easier to mount electronic circuits such as drive circuits within the module.

(b) When the drive circuit is placed near the semiconductor laser, the wiring length can be shortened and lead inductance can be reduced.

This improves the waveform response of the output light of the semiconductor laser and facilitates high-speed modulation.

(c) Since the number of parts in the optical system is reduced, the process for modularization is simplified.

As mentioned above, the miniaturization of optical systems is coupled with the increase in speed and capacity of optical communication systems, and the demand for compact optical modules using single-axis mode lasers and single-mode optical fibers is increasing. It's becoming important.

[Problem to be solved by the invention]

The structure of a conventional coupling system in which the end face of an optical fiber is processed is
As shown in the figure, a spherical fiber (strand) 22 passed through a metal pipe 20 and fixed with a solder 21 is directly coupled to a semiconductor laser 23 . In this case Puipu 20
is fixed onto the base 24 by YAG laser welding, soldering with an ultrasonic soldering iron, or the like.

However, when the heat sink 26 to which the semiconductor laser 23 is fixed is mounted on the substrate 24, the thickness of the fixing solder 25 varies in the range of 50 to 100 μm. For this reason, there is a problem in that optical axis deviation occurs while the vibrator 20 is being fixed due to the large degree of increase in loss due to axis deviation of the tip spherical fiber 22, and as a result, sufficient fiber input cannot be obtained.

An object of the present invention is to provide a semiconductor laser unit with an optical fiber that eliminates the above-mentioned drawbacks.

[Means to solve the problem]

The optical fiber-equipped semiconductor laser unit of the present invention is configured as a single-axis mode laser that is divided into a laser oscillation section and a groove forming section along the cavity axis direction, and the laser oscillation section has a diffraction grating near the active layer. The semiconductor laser includes a semiconductor laser, and an optical fiber whose terminal portion is fixed onto the groove of the groove forming portion and is optically directly coupled to the light emitting surface of the laser oscillation section, and includes the terminal portion of the optical fiber. It is constructed by covering the periphery with an optically transparent adhesive.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view of an embodiment of the present invention, and FIG. 2 is a front view of the embodiment.

The semiconductor laser 30 includes a laser oscillation section 31 and a groove forming section 32.
It is divided into. The laser oscillation unit 31 is a diffraction grating 33
This is a single-axis mode laser in which the active layer 34 is provided near the active layer 34. A groove 36 for fixing the fiber end portion 35 to which the output light from the laser oscillation portion 31 is coupled is formed in the groove forming portion 32 . This fiber terminal section 35 and laser oscillation section 31
The periphery of the fiber end portion 35 is covered with an optically transparent adhesive 37, and the adhesive 37 is also used to fix the fiber end portion 35 to the groove 36.
Power is being used.

Here, a method of manufacturing the trapezoidal groove 36 will be explained.

A semiconductor layer is laminated on the (011) plane semiconductor substrate 38, and an electrode metal 39 is deposited to complete the crystal growth of the semiconductor laser wafer. When forming the groove 36 by etching,
First, the electrode metal 39 of the groove forming portion 32 is removed to expose the semiconductor surface. Next, silicon nitride (S i
In order to use the 3N4) film as a mask, it is brought into close contact with the semiconductor surface by plasma CVD. The Si3N film in a portion corresponding to the width of the groove 36 is removed using buffered hydrofluoric acid.

When etching a semiconductor layer, in the case of indium phosphide (Ink), a bromomethyl solution containing 2.5% bromine dissolved in methyl alcohol is used, and in the case of indium gallium arsenide phosphide (InGaAsP), Potassium hydroxide, potassium ferrocyanide and water: 2:
An etching solution with a mixing ratio of 1:6 is used. By using the above etching solution together, the cut surface (111
) A V-groove or trapezoidal groove is formed. The cut angle θ at this time is 54.74°.

The width W of the groove 36 in which the fiber end portion 35 is mounted must be etched with high accuracy. Now, assuming that the layer thickness from the topmost semiconductor layer to the active layer 34 is t, and the outer diameter of the fiber wire is l, the following equation must be satisfied in order for the center of the fiber core to coincide with the height of the active layer. There is a need.

W= 2 (u + t cosθ)/sinθ normal t
is 2 μm and (l is 125±1 μm, so the range of W should satisfy 154.7 μm≦W≦157.1 μm.

When the fiber end portion 35 is mounted in this groove 36, the deviation from the optimum position in the direction perpendicular to the bonding surface is at most 1.
7 μm, therefore, the optical output fluctuation before and after mounting can be reduced to 0.
It can be suppressed to within 5dB.

In this embodiment, the fiber end portion 35 has a radius of curvature of 40 μm for the purpose of increasing coupling efficiency and protecting the fiber end face.
Adopts a tip fiber. Therefore, at worst it is -6 dB.
The coupling efficiency of the pedestal is possible.

Next, the adhesive 37 used to fix the fiber end portion 35 is
I will explain about it. The adhesive 37 is used for fixing the fiber end portion 35 and between the light emitting surface of the oscillating section 31 and the fiber end portion 35 .

Since the laser oscillation unit 31 used in this embodiment is a single-axis mode laser, it does not require a folded surface like the Fabry-Perotype. Actually, the adhesive 37 is the laser oscillating part 3.
Since the reflectance changes upon contact with the light emitting surface of No. 1, there may be slight variations from the initial values of the laser current threshold and differential quantum efficiency, but there is almost no need to consider the effect on the characteristics.

In the actual example shown in FIG.
Although the area near the boundary between the two is filled with adhesive, it is also possible to fill the entire semiconductor laser 30 and fiber end portion 35 with adhesive. Since the refractive index of the normal adhesive 37 is around 1.5, the Fabry-Perot mode problem can be eliminated by applying an anti-reflection coating to the light emitting surface of the semiconductor laser 30 that matches the refractive index of 1°5. .

〔Effect of the invention〕

As explained above, the present invention has a small optical axis shift when fixing a fiber end, and can suppress a drop in light output power to a small extent. Therefore, the coupling efficiency of -10 dB, which was considered in the conventional fiber processing method, can be reduced to 10 dB. This can be improved to about 6 dB, and since the semiconductor laser and the fiber terminal are integrated, it has the effect of being stable against changes over time.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a front view of the embodiment shown in FIG. 1, and FIG. 3 is a side view of a conventional example. 30... Semiconductor laser, 31... Laser oscillation section, 32... Groove forming section, 33...
・Diffraction grating, 34...active layer, 35...
Fiber terminal section, 36... Groove, 37...
・Adhesive, 38...Semiconductor substrate, 39...
...electrode metal.

Claims (1)

[Claims] a semiconductor laser configured as a single-axis mode laser that is divided into a laser oscillation part and a groove forming part along the cavity axis direction, and the laser oscillation part has a diffraction grating near an active layer;
an optical fiber whose end portion is fixed onto the groove of the groove forming portion and is optically directly coupled to the light emitting surface of the laser oscillation section; the periphery of the semiconductor laser including the end portion of the optical fiber is optically connected A semiconductor laser unit with an optical fiber, characterized in that the semiconductor laser unit is coated with a transparent adhesive.