JPS62241388A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To decrease the beam breadth of laser beams oscillated from a plurality of laser elements by integrally mounting the laser elements and a reflector reflecting laser beams emitted from the laser elements to a substrate, reflecting laser beams emitted from the laser elements by the reflector and irradiating the laser elements by reflected beams as return beams. CONSTITUTION:A plurality of laser elements 17 are formed onto a substrate 11, and a crystal layer 18 consisting of a waveguide layer 13 shaped in case of the formation of the laser element 17, an active layer 14 and a clad layer 15 is shaped as a reflector 20 by forming a groove 19 through etching at a predetermined interval l from the end surface 14A of the active layer 14 where opposite to the end surface 14A of the active layer 14, from which laser beams are emitted, in the laser element 17. Since such a reflector 20 is shaped, laser beams emitted from semiconductor laser elements 17 and 22 can be projected mutually to other laser elements 17, 22, preventing the dissipation of beams by using the reflector 20. Accordingly, the beam breadth of the outgoing beams of laser beams emitted from the laser elements l7, 22 can be narrowed.

Description

[Detailed Description of the Invention] C Summary] A semiconductor laser device that reduces the line width of a laser beam emitted from a semiconductor laser element, which comprises a plurality of laser elements on the same substrate and a laser beam emitted from the laser elements. By integrally forming a reflector that reflects the laser beam using the same method and introducing the laser beam emitted from the laser element as return light to the laser element via the reflector, the laser beam emitted from the laser element can be reflected. Semiconductor laser device that reduces inconvenience.

[Industrial application field]

The present invention relates to a semiconductor laser device that reduces the line width of laser light emitted from a semiconductor laser element.

Semiconductor laser elements are used as light sources in optical communication systems because they have low power consumption and are capable of high-speed modulation.

The beam diameter of the laser beam emitted from such a semiconductor laser device, that is, the linewidth of the laser beam, is about 100 MHz, but if this is further used in a coherent optical communication system, the laser beam emitted from the laser device It is required that the linewidth of light be reduced to below I MHz.

[Conventional technology]

Conventionally, in a semiconductor laser device in which the line width of such a laser element is reduced, a reflecting mirror 3 such as a plane mirror is installed on a base 2 on which a laser element 1 is installed, and the laser element 1 and the reflecting mirror are connected to each other. 3 forms a cavity oscillator.

In this way, a resonator is also formed between the end faces IA and IB of the laser element 1, and the resonator is formed between the end faces 18 and IB of the laser element 1.
The length l of the resonator formed by B and the length L of the resonator formed between the laser element 1 and the reflecting mirror 3 are different. Different standing waves can be obtained.

Therefore, when standing waves formed by two resonators compete with each other, which of the standing waves becomes stronger is determined by the oscillation wavelength of the laser light emitted from the laser element.

In other words, the standing waves having wavelengths other than the oscillation wavelength of the laser beam bind each other and concentrate energy on the oscillating laser beam, and due to this concentration of energy, the laser beam emitted from the laser element The line width of the light begins to decrease.

[Problems to be Solved by the Invention] However, if you use a reflecting mirror such as a plane mirror to return the light emitted from the laser element and use this returned light to reduce the line width of the laser beam, this reflecting mirror Since the light in the entire wavelength range of the light emitted from the laser element returns as return light, when increasing the intensity only at a specific wavelength or when selecting a wavelength, the concentration of energy is poor and the laser The line width of the laser beam emitted from the element is wide (this causes a drawback).

Therefore, there is a method that uses a laser element that oscillates at a single wavelength and uses a diffraction grating instead of a reflecting mirror to return the laser beam, but this method requires a large-scale device.
Furthermore, when using this device, there is a drawback that a desired line width cannot be obtained unless the temperature of the diffraction grating is accurately controlled.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser device which eliminates the above-mentioned drawbacks, has a simple structure, is compact, and can easily narrow the line width of the laser beam.

[Means for solving problems]

The semiconductor laser device of the present invention includes a plurality of laser elements formed on the same substrate in the same process, and a reflector that reflects the laser light emitted from the laser element, which is integrally provided on the substrate, and The emitted laser light is reflected by the reflector and the reflected light is irradiated to the laser element as return light, thereby reducing the line width of the laser light emitted from the laser element.

[Effect]

The semiconductor laser device of the present invention is manufactured using a process similar to that of forming a plurality of laser elements on a semiconductor substrate, and a reflector for returning light emitted from the laser elements on the same substrate. Even when there are temperature fluctuations, a large number of laser elements with approximately the same oscillation wavelength can be formed, and return light in a mode similar to the mode of the laser beam emitted from the laser element can be formed. By using this returned light, wavelength selectivity is enhanced and energy concentration is improved, thereby effectively reducing the line width of the laser beam emitted from the laser beam.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing the structure of a semiconductor laser device of the present invention, and FIG. 2 is a sectional view taken along the line nn'.

In this example, Distributed-Feedback
An example of a semiconductor laser device using a k-Laser (hereinafter referred to as a DFB laser element) will be explained.

As shown in FIGS. 1 and 2, a diffraction grating 12 is formed on a substrate 11 made of indium-phosphorous (InP) using a photolithography method, and a diffraction grating 12 is provided on the substrate 11 for transmitting laser light. gallium-indium-
A waveguide layer 13 made of arsenic-phosphorus (InGaAsP) is formed by a liquid phase epitaxial growth method, and an active layer 14 made of 1nGaAsP that oscillates and emits a laser beam is further formed thereon by a liquid phase epitaxial growth method. .

Furthermore, on top of that, the laser light oscillated in the active layer is confined,
Craft layer 15 made of InP to increase oscillation efficiency
Further, an electrode 16 made of gold (Au) or the like is formed by vapor deposition on the electrode 16 for operating the laser element.

A plurality of such laser elements 17 are formed on the substrate 11, and when forming the laser elements 17, the laser elements 17 are formed at a position facing the end surface 14A of the active layer 14 from which the laser light of the laser elements 17 is emitted. waveguide layer 13, active layer 1
4. The crystal layer 18 made of the cladding layer 15 is formed on the end surface 14A.
A groove 19 is formed by etching at a predetermined distance @1'.
The reflector 20 is formed by forming the reflector 20.

Since the reflector 20 is formed on the same substrate 11 in the same process as the laser element 17, it can be easily formed by a simple method and without much effort.

Furthermore, since the end surface 21 of the reflector 20 formed opposite to the end surface 14A is mirror-finished by etching,
It has the function of a reflecting mirror similar to a plane mirror.

In this way, by having the reflector 20, the laser beams emitted from the semiconductor laser elements 17 and 22 are directed to the other laser elements 17 and 22 while preventing the light from dissipating using the reflector 20. The line width of the laser beam emitted from the laser element 17.22 can be narrowed.

In addition to the above embodiments, as shown in FIG.
By providing a U-shaped second reflector 31 at approximately the same height as the reflector 20 so as to surround the reflector 20, the returned light can be more effectively injected into the laser element 17.22. I can do it.

As another example, it is more effective to deposit a metal film with high reflection efficiency on the surface of the reflector 20.31 facing the end surface 14^ of the active layer 14 from which the laser beam is emitted. be.

〔Effect of the invention〕

As described above, the semiconductor laser device of the present invention
), the returned light emitted from the laser element can be injected into the laser element using a simple method, so a high-performance semiconductor laser device that can be used for coherent optical communication with a reduced line width of laser light can be obtained. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the semiconductor laser device of the present invention, FIG. 2 is a cross-sectional view taken along line 1--1 in FIG. 1, and FIG. FIG. 4 is a schematic diagram showing the main parts of a conventional semiconductor laser device. In the figure, 11 is a substrate, 12 is a diffraction grating, 13 is a waveguide layer, 14 is an active layer, 14A is an end face of the active layer, 15 is a cladding layer, 16 is an electrode, 17.22 is a laser element, and 18 is a crystal. 19 is a groove, 20.31 is a reflector, and Zl is an end face of the reflector. Heather structure Watsuki O half praying - The & 1 plane day 1 time Wataru - X
/ father-in-law 11 Rei, n cross-section ω Fig. 2 1 to (plane whistle 3 [q

Claims (1)

[Claims] A plurality of laser elements (17, 22) formed on the same substrate (11) in the same process, and the laser element (17, 22)
A reflector (20) for reflecting laser light emitted from the laser element (17) is integrally provided on the substrate (11).
, 22), the laser beam emitted from the reflector (20)
A semiconductor laser device characterized in that the reflected light is reflected by a laser element (17, 22) and irradiated as return light.