JPS63287084A - Semiconductor laser module - Google Patents

Abstract

PURPOSE:To improve reliability and coupling efficiency, by burying an optical fiber in a light taking-out part of a surface emitting type laser for directly coupling laser beam with the optical fiber. CONSTITUTION:A surface emitting type laser 2 is die-boneded on a stem 1 followed by die-bonding of the light-receiving surface of a monitor diode 3 and an outgoing window 4 of laser light together. Next, a core 5 of an optical fiber is put in the other outgoing window 6 of the laser 2 and a housing is soldered on the electrode surface 7 of a chip. Further, the electrode surface 7 is wire-bonded with a cathode lead 8, and the electrode surface of the monitor diode 3 is wire-bonded with a lead 9. Thereon a cap 11 is put to form a laser module. With this constitution, the coupling efficiency of laser beam and an optical fiber is as high as 40% on the average, having no tempera-ture fluctuation of light output of fiber and a monitor diode output, while improving reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to improvements in light sources for fiber optic communications.

Conventional Technology Up until now, single mode fiber optics have been used to perform long distance and large capacity optical fiber communications, with an oscillation wavelength of 1.
Laser modules that are highly efficiently coupled with semiconductor lasers of 3 μm to 1.5 μm have been used. In general, semiconductor lasers (hereinafter abbreviated as lasers) have an elliptical pattern with a beam output angle of about 35 degrees in the vertical direction θ and about 25 degrees in the horizontal direction, and a single core system of about 8 μm. Coupling with a mode fiber is extremely difficult, and a coupling efficiency of about 40% can only be obtained through a complicated lens system. −
As an example, FIG. 3 shows a coupling system between a laser and a single mode fiber. The elliptical emitted light from the laser 41 is turned into parallel light by a ball lens 42, and then condensed by a rod lens 43 and input into a fiber 44. In such a coupling system, the axis misalignment of the rod lens 43 and the fiber 44 significantly deteriorates the coupling efficiency. In other words, it affects the reliability with respect to environments such as temperature and vibration. In addition, in conventional laser modules,
The structure is such that the light emitted from one principal surface of the laser enters the fiber, and the light emitted from the other surface enters the monitoring photodiode. That is, since the laser light output has a strong temperature dependence, the light output is constantly monitored as an electrical output by a photodiode, and fed back to the laser operating current to maintain a constant output.

This monitoring photodiode is generally mounted on the same stem as the laser, but when both are die-bonded, if the ohmic electrodes are made of the same material, one of them will inevitably be misaligned. Therefore, measures such as using a low melting point solder material for one of the chips have been taken.

The problem that the invention aims to solve In conventional laser modules such as the above, a ball lens is used.

The use of a rod lens or the like causes fragility in environmental resistance characteristics, and the use of materials with different melting points for the monitor photodiode electrode and the laser electrode causes a decrease in reliability due to a difference in thermal expansion coefficient.

Therefore, the present invention provides a semiconductor laser module with an extremely simple coupling system that solves the above-mentioned problems.

Means for Solving the Problems The present invention provides a semiconductor laser having an active waveguide provided in parallel on a semiconductor substrate and a mechanism for extracting the light beam emitted within the active waveguide from two locations on the substrate side. An optical fiber is embedded in a groove-shaped circular window provided in a light extraction section on the substrate, and a laser beam is coupled to the optical fiber.

A surface-emitting type laser can obtain laser light with a narrower width than a normal laser, and because it is simply connected directly to an optical fiber, high reliability and high coupling efficiency can be obtained.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a sectional view of a semiconductor laser module of the present invention. The semiconductor laser used was a surface emitting type semiconductor laser described in Japanese Patent Application No. 61-92725. A cross-sectional view of this laser is shown in the second
As shown in the figure. n −1 nGa s on the n-InP substrate 21
P processing stop layer 22゜n-InP cladding layer 23, n-InGaAsP active layer 24, p-In
P cladding layer 25, p-InG4A! An IP cap layer 26 has been grown. Both ends of the active layer 24, which is a light emitting part, are cut at 45 degrees, and the emitted light is guided in the direction of a circular window 30 provided in the substrate. 27 and 28 are ohmic electrodes. 5i5N4/5i inside the circular window 3o
02 multilayer film 31 is attached, and a SiO2/Si/Au reflective film is provided on the cut surface, so that part of the light is returned to the outside and part of it is returned to the active layer, forming a resonator as a whole. It emits laser oscillation. In a laser with this structure, unlike a conventional laser in which the end face is made into a mirror surface by cleavage, the beam spread angle can be made extremely small. That is, in the conventional laser, the emission angle from the active layer into the air is wide as described above, but in this laser, it can be narrowed to about 9 degrees.

As shown in FIG. 1, such a laser 2 is die-bonded onto the stem 1 with the substrate surface facing upward. The monitor diode 3, the light-receiving surface, and the laser beam output window 4 are successively die-bonded together. Next, the optical fiber core wire 6 is inserted into the other exit window 6 of the laser 2.

The diameter of the fiber 5 is 126μ, and the diameter of the exit windows 4, 6 is about 120μ. The outer sheath of the fiber is metallized and soldered to the electrode surface 7 of the chip.

Next, the electrode surface 7 is wire-bonded to the canned lead 8, and the electrode surface of the monitor diode is wire-bonded to the lead 9. Note that the anode electrode 1o is electrically connected to the die bonding surface of the laser 2. This is covered with a cap 11 to complete the laser module.

In such a configuration, the coupling efficiency between the laser and the optical fiber can be increased to an average of 40
It is possible to obtain a high coupling efficiency of about 10%, and at the same time
There is no change in the fiber optical output or the output of the monitor diode even if a temperature cycle test of "C" is performed.

Furthermore, since the monitor diode can be attached in the same process as the die bonding of the laser chip, productivity is extremely high and bonding can be performed without using low melting point solder, so the stable characteristics described above can be obtained.

Effects of the Invention As described above, according to the present invention, it is possible to provide a laser module with high coupling efficiency and reliability using an extremely simple coupling system by directly coupling a surface emitting laser to a fiber.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a laser module according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of a laser chip used in the module shown in Fig. 1, and Fig. 3 is a cross-sectional view of a conventional laser and optical fiber. FIG. 2 is an explanatory diagram of a coupling system. 1... Stem, 2... Laser chip,
3...Monitor diode, 4.6...Output window, 5...Optical fiber, 7...Electrode,
8,9.10...Lead, 11...Cap. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 21 - n-1nP ridge 22 - n-1nGaASP processing stop layer 2'll - n-1nP quadruple layer % - n-1nGaAsP active layer As-P-InP quad layer 26 - P-InGaASP capping layer 2' 1d-Ohmic holder 29 = 5i0215i/AU reflective film sword--Circular type 31-5r3Nt/5j (h Multilayer film Fig. 2 Figure 3

Claims (2)

[Claims] (1) It has an active waveguide provided in parallel on the semiconductor substrate and a mechanism for extracting the light beam emitted within the active waveguide from two locations on the substrate side, and is provided in the light extraction section on the semiconductor substrate. 1. A semiconductor laser module characterized in that an optical fiber is embedded in a groove-shaped circular window, and a surface emitting laser beam is coupled to the optical fiber. (2) The semiconductor laser module according to claim 1, characterized in that a photodiode is mounted on the groove-shaped circular window on the substrate side.