JPS58110087A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To enhance the reflection factor of the oscillation wavelength for the titled laser device by a method wherein a reflecting layer, consisting of a multilayer film of different composition ratio and having a specific film thickness at the end face of a semiconductor laser element being made of the same material as a laser crystal, is provided. CONSTITUTION:In the GaAlAs laser having a double heterojunction, the reflection layer 10 to be provided on the above is composed of the laminated material of periodic repetition of a multilayer film 11 which constitutes two or more kinds of different composition, although having the same ingredient as the GaAlAs. Thus, the wavelength is selected by a reflection layer 10, and the specific wavelength only is reflected. If the (y) of an N type Ga1-yAs active layer is 0.08, the multilayer 11 is composed of a Ga1-aAlaAsa film 11a and a Ga1-bAs film 11B for a wavelength 8,300Angstrom , and a refractive index of approximately 1% is generated between the two films by having 0.1 for (a) and 0.18 for (b). Also, the total film thickness of the two films is made to 1,180Angstrom that is lambda/2n=1,180, and the reflection layer 10 is obtained by growing the above to 50 periods or thereabouts.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a semiconductor laser device, particularly to a structure provided with a novel reflective layer.

(2) Conventional technology and problems Semiconductor laser devices are oscillators that are attracting attention for optical communications, but as a laser device for this bridge, distributed reflectors (
Distribution@d Bragg R@fl@ct
A structure is known in which a single-axis mode oscillation is achieved by providing a single-axis mode oscillation.

Figure 1 shows an example of the cross-sectional structure.
I As A diffraction grating 1 with a precise waveform of 4 (in the case of oscillation wavelength and +1 indicates the refractive index) or an integer multiple thereof is formed over a long distance on the side end face of the laser element L1 Distribution by this grating 1 Shape reflection takes place. In the figure, 2 is the P electrode, 3 is the Yap layer in P-GaAl, and the rumor is that the P
-Ga1-, AI! As cladding layer, 5 is P or n-
Ga1-y Aly As active layer, 6 is n-G&11A
1. As cladding layer, 7 is n-GaAs substrate, 8 is h
The electrodes are shown and the lattice is formed in the cladding layer or the active layer. This type of diffraction grating 1 is formed by patterning a photoresist group using optical interference of a laser beam, and then chemically etching it to form a waveform on the crystal plane.The waveform is determined by the waveform of the laser light source. is applied, but it is difficult to accurately and reproducibly form long distances, and there is a drawback that the lattice disorder results in a low Lit value.

In addition, distributed feedback lasers (Distributed F lasers)
eedBack La5er) also has a similar lattice formed in its active layer, but the formation is similarly spaced apart.

(3) Purpose of the Invention In view of the above drawbacks, the present invention proposes a semiconductor laser device having a distributed reflector formed without chemical etching.

(4) Structure of the Invention The object of the invention is to provide a reflective layer on the end face of a laser element, which is a multilayer film having a film thickness of Ka or an integral multiple thereof, and made of the same material as the laser crystal and having a different crystal composition ratio. This can be achieved using a semiconductor laser device.

(5) Examples of the invention To explain the following with examples, the 211th embodiment of the invention will be described with reference to examples.
a It is a sectional view applied to an AI As laser. As shown in the figure, the reflective layer 1O has the same component as GaAlAl of the double heterojunction, and two or more multilayer films 11 with different compositions are periodically laminated, and this reflective layer 1O provides strong wavelength selection. As a result, specific wavelengths are strongly reflected, resulting in single-axis mode oscillation.

For example, n-Ga1-, A1yAa active layer 5 is yo,
In the US laser device, for a wavelength of 8300 people, the multilayer film 11 is Ga, AI, As1l [11A and Ga1
-bAlbA- film JIB, a-0,L b
-0.18, there will be a refractive index difference of about 1% between the two films, and the total thickness of both films will be 1180 layers, that is, A=1180, and this will be grown to 50 cycles #M degrees to form a reflective layer. If it is lO, the laser beam with the wavelength of 830 (lλ) can be strongly reflected, and a laser device with a single axis mode oscillation with a low threshold value can be obtained.

The reflective layer made of such a multilayer film can be formed with high precision using molecular beam epitaxial growth. That is, in the molecular beam epitaxial growth method, each molecular beam source cell containing Ga, AI, and As is heated separately in an ultra-vacuum and emitted, so the I of the component composition is
11 is easy, and the firing rate can be set to 1 atomic layer/second, so the controllability of the film thickness is extremely excellent.

Therefore, the above lI thickness of 1180λ is converted to G with a film thickness of 590^.
Joban AIO, l A8 conversion 11A and film thickness 5901"0.
11 AI (1,, sAs film 11 B), which are periodically stacked to form 50 layers, can achieve quotient accuracy.

(6) Effects of the Invention As is clear from the above embodiments, the present invention has a reflective layer structure formed from a multilayer film that is a reflector, and has a higher precision than the conventional waveform grid formed by chemical etching. Since it can be formed into a thin film, the reflectance of the oscillation wavelength is improved, a stable low threshold value can be obtained, and this significantly contributes to improving the quality of semiconductor laser devices. It goes without saying that in addition to the above-mentioned Ga AI As laser, the present invention can also be applied to, for example, an InGaAaP laser device.

[Brief explanation of the drawing]

FIG. 1 shows a semiconductor laser device having a conventional distributed reflector, and FIG. 2 shows a semiconductor laser device having a distributed reflector according to the present invention. In the figure, 1 is a conventional wave-shaped diffraction grating, the side is a reflective layer according to the present invention, and 11 is a multilayer film. Figure 1 Figure 2 Figure 1

Claims (1)

[Claims] λ (λ: laser oscillation wavelength, 1
1: refractive index) or an integral multiple thereof, and is provided with a reflective layer formed by laminating a plurality of multilayer films made of the same material as a laser crystal and having different crystal composition ratios.