JPS63289984A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To realize laser, which oscillates in a single vertical mode, in a simple process and without deterioration in substrate's strength, by providing multilayered films which comprise specific semiconductor layers and forming an inclined terminal plane, to face the semiconductor surface plane, on at least one side out of optical waveguide directional ends of an active layer. CONSTITUTION:A first clad layer 2, an active layer 3, a second clad layer 4, and multilayer films 5 formed by laminating semiconductors of n1 and n2 refractive indexes alternately in respective thicknesses of 1/4n1 and 1/4n2, are laminated in order on a semiconductor substrate 1. An inclined terminal plane is formed, to face the semiconductor substrate plane, on at least one side out of optical waveguide directional ends of the active layer 3. For example, an InGaAsP active layer 3 is formed on an InP substrate 1 so that it is interposed between InP clad layers 2 and 4. Semiconductor multilayered films 5 comprising InP and InGaAsP layers, and a cap layer 6 are laminated on the clad layer 4. High reflection multilayer films 9 composed of dielectrics on cleavage planes are formed on one end of the active layer 3, and the inclined terminal plane is formed on the other end so that it faces the substrate surface in an angle thetaof 45 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser that can be used as a light source for optical communication systems and optical memories.

BACKGROUND OF THE INVENTION Single-longitudinal mode semiconductor lasers are essential for increasing the capacity of optical communication systems and optical memories. Semiconductor lasers having a distributed feedback (DFB) structure or distributed reflection (DBR) structure are common as single-longitudinal mode lasers, and excellent characteristics are obtained with such structures.

On the other hand, the manufacturing process is easier than that of DFB and DBR structures.
A structure as shown in FIG. 2 has been proposed as a semiconductor laser structure capable of realizing single-longitudinal mode oscillation. In this structure, on the semiconductor substrate 11, the refractive index is n 1r n
A semiconductor multilayer film 12 consisting of 2 semiconductors is alternately formed to a thickness of 2% of zn1 wavelength and n2 wavelength, a first cladding layer 13, an active layer 14, and a second cladding layer 15. The end face of the active layer 14 in the waveguide direction is processed into a 45° inclined end face 16, and has a multilayer reflective film 17 on the face. A hole 18 that extends up to the multilayer film 12 is provided in the semiconductor substrate 11 at a portion corresponding to the center, and the laser beam is
Take it out from the hole 18.

Problems to be Solved by the Invention The proposed semiconductor laser requires a great deal of skill, as it requires a process of drilling a hole with a depth of 100 μm or more by etching or the like to extract light from the back surface. Also thickness 150
The strength of the substrate is also an issue because a deep hole is drilled in a substrate with a thickness of about 1.0 μm, leaving a thickness of several μm on the surface.

The present invention aims to realize a laser that oscillates in a single longitudinal mode through a simple process without impairing the strength of the substrate.

Means for Solving the Problems A semiconductor laser according to the present invention has at least a first cladding layer, an active layer, a second cladding layer,
Semiconductor layers with refractive indices of n 1 and n 2 alternate! , /4n1 wavelengths 2%n2 wavelengths are sequentially laminated, and at least one end of the active layer in the optical waveguide direction has an inclined end face facing the semiconductor substrate surface. It is something.

Function The present invention has the above-described configuration, so that excitation light excited in the active layer and traveling in a direction parallel to the substrate is reflected in a direction opposite to the substrate at an inclined end face facing the substrate surface. A part of the reflected light has a refractive index of nl.

The semiconductor consisting of n2 is alternately transmitted through the multilayer film formed to have a thickness of %n1 wavelength + X n2 wavelength, but a portion is reflected and returns to the inclined end face. The returned light is again reflected by the inclined end face, and becomes light that travels through the active layer in a direction parallel to the substrate. By constructing a laser resonator with the multilayer film, the inclined end face, and the active layer in this manner, the laser light is transmitted through the multilayer film and emitted in the opposite direction to the substrate.

On the other hand, since the multilayer film is composed of a semiconductor film with a thickness of %n1 wavelength + oscillate.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross section of a semiconductor laser according to an embodiment of the present invention. In FIG. 1, 1 is an InP substrate of a semiconductor laser. An active layer 3 of InGaAsP with a band gap of 1.3 μm is formed on the InP substrate 1.
It is formed between nP cladding layers 2 and 4. On the cladding layer 4, a semiconductor multilayer film 5 made of InP and InGaAsP, a cap layer, etc. are laminated.

The semiconductor multilayer film is InP with a refractive index of 3.2, and InGaA with a refractive index of 3.2.
That of sP is 3.4, and in this case the wavelength is 1.3 μm.
Therefore, the respective film thicknesses are 0.102 μm and 0.096 μm.
Set to μm.

One end of the active layer 3 is an end surface formed by the interbone, and a highly reflective multilayer film 9 made of dielectric material is formed on the surface, and the reflectance is approximately 100%. . On the other hand, the other end is an inclined end face facing the substrate surface. In this example, the angle θ is 45°. Such an inclined end surface is
In reactive ion etching or reactive ion beam etching, it can be easily formed by tilting the substrate with respect to the ion acceleration direction. It is also possible to form a dielectric multilayer film on this inclined surface and design the reflectance to an arbitrary value.

Direct current injection is carried out by means of electrodes 7, 8, at the top, -E
A laser light output window 1o is formed in a part of the pole 8. A dielectric multilayer film for adjusting the refractive index may also be formed on this window.

Note that the characteristics of the resonator of the semiconductor laser are determined by appropriately selecting the number of layers of the semiconductor multilayer film 5, the reflectance of the high-reflection multilayer film, and the reflectance of the multilayer film formed on the inclined end face and the 1° laser light output window. Can be selected arbitrarily.

This makes it possible to control the oscillation threshold current, optical output, longitudinal single mode Note, etc., and if the optimum is selected, the excavation threshold is 30 mA.
Single-longitudinal mode laser light can be extracted in the direction perpendicular to the substrate.

Effects of the Invention With the semiconductor laser structure according to the present invention, a single
A semiconductor laser that oscillates in a longitudinal mode can be easily manufactured with a high yield. Furthermore, since the optical output of the semiconductor laser according to the present invention is emitted in a direction perpendicular to the substrate, the inspection process can be performed on a wafer-by-wafer basis, and productivity can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor laser according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional semiconductor laser. 1... InP substrate, 2... InP cladding layer, 3... InGaAsP substrate, 4...
... InP cladding layer, 5 ... semiconductor multilayer film, 6 ... cap layer, 7 ... electrode, 8
・・・・・・Electrode, 9・・・High reflective polyurethane, 1
0... Laser light output window, 11... Semiconductor substrate, 12... Semiconductor multilayer film, 13...-
...First cladding layer, 14... Active, bitter, 15
...Second cladding layer, 16...Slanted end surface, 17...Multilayer reflective film, 18...Drilling part, 19...Electrode, 20... Electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] A multilayer in which at least a first cladding layer, an active layer, a second cladding layer, and a semiconductor having a refractive index of n_1 and n_2 are alternately formed to have a thickness of 1/4n_1 wavelength and 1/4n_2 wavelength on a semiconductor substrate. 1. A semiconductor laser, wherein films are sequentially laminated, and at least one end of the active layer in the optical waveguide direction has an inclined end face facing the semiconductor substrate surface.