JPS58199586A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To unify longitudinal mode of a semiconductor laser by providing in parallel a plurality of laser resonators of different resonance lengths in the vicinity of one light waveguide. CONSTITUTION:N type GaAlAs layer 2, P type GaAs layer 3, P type AlGaAs layer 4 and P type GaAs layer 5 are sequentially laminated on an N type GaAs substrate 1 in a semiconductor laser, striped electrodes 20, 21 are aligned in parallel in the vicinity on the upper surface. Thus, resonators corresponding to the electrodes 20, 21 are formed on the layer 3. The laser lights which are generated from two resonators are electromagnetically operated to each other, the laser resonator of long side is oscillated in sole longitudinal mode of the laser resonator of short side, and the longitudinal modes of the output lights obtained from both the laser resonators becomes sole mode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to semiconductor lasers, and particularly to a semiconductor laser that unifies longitudinal modes.

1- As a conventional semiconductor laser, one shown in FIG. 1, for example, is known. In FIG. 1, this semiconductor laser is a type of gain-guided type semiconductor laser, and an n-ktG-containing B layer 2 is grown on an n-G□A8 substrate 1 by epitaxial growth.
, p-G, AS layer 3, p-AtG, As layer 4 and p-
G-As layers 5 are sequentially laminated, and striped electrodes 6 and lower electrodes 7 are provided on this semiconductor crystal. The stripe electrode 6 limits the region of current passing through the p-G, A8 layer 3 only to the downward direction of the p-G, A8 layer 3.
High-density carriers are injected into the G, AS layer 3 along the stripe electrode 6. The p-GtAa layer 3 is an active layer that performs laser operation, and has a forbidden band width and a refractive index of p-GtA.
n-AtG different from S layer 3, As layer 2, p-AtG,
It is sandwiched between As layers 4 and has a double heterostructure. In other words, the forbidden band widths of the n Atq, As layer 2 and the p AtGLAB layer 4 are as large as that of the p-GLAa layer 3, and due to the potential barrier formed at these junction surfaces, the injected carriers are transferred into the p-GLAS layer 3. , the electron-
Stimulated emission light (laser light) 2- is efficiently generated by recombination of holes. This light emitting region is the stripe electrode 6
formed along the Also, n-AtG, A8 layer 2, p
Since the refractive index of the -AtG□A8 layer 4 is smaller than that of the I) -GeA8 layer 3, p -G,1 Aal 3 becomes the core and forms an optical waveguide, and the laser beam is guided through this optical waveguide. Trapped within the wave channel. The end faces of the semiconductor crystal on both ends of the stripe electrode 6 are constituted by open arms of the crystal, which serve as reflective mirror surfaces. As a result, a laser resonator having a constant resonator length t is formed in the optical waveguide along the stripe electrode 6, and the laser light propagating in the longitudinal direction is resonantly amplified.

By the way, in such a gain waveguide semiconductor laser, since the reflective mirror surface of the laser resonator is formed by the arm-opening plane of the crystal, the resonator length t is much larger than the wavelength of the light wave. . In other words, since a plurality of light waves can exist in this resonator, the longitudinal mode becomes multimode.

This is extremely inconvenient as a light source for optical communications, and unification of the longitudinal mode is required. Note that the unification of the horizontal transverse mode is ensured by narrowing the width of the stripe electrode 6, and the unification of the vertical transverse mode is ensured by reducing the thickness of the p-G and AS layers 3. To is a well-known rule.

In order to unify the longitudinal mode, it is sufficient to shorten the resonator length t, but this is not easy because the reflecting mirror surface is formed by the arm-opening plane of the crystal. Therefore, D F B (D
Distributed Feed Back) laser and DBR (Distributed Bragg Ref
(lec-tor) lasers have been developed. However, with these lasers, periodic structures such as diffraction gratings must be created at pitch intervals on the order of several microns, and it is difficult to create such structures with high precision, and there are still limits to the pitch intervals that can be created. There were drawbacks such as:

This invention was made in view of these conventional problems, and its purpose is to bring laser resonators with different lengths close enough to each other to achieve
An object of the present invention is to provide a semiconductor laser in which longitudinal modes can be easily unified.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Incidentally, since the crystal composition of the semiconductor laser is the same as that shown in FIG. 1, the same reference numerals are given and the explanation thereof will be omitted.

FIG. 2 is a schematic diagram showing a semiconductor laser according to the present invention, in which two stripe electrodes 20° and 21 are arranged in parallel sufficiently close to each other on the upper surface of the semiconductor crystal shown in FIG. Then, one end face of the semiconductor crystal to which one stripe electrode 21 belongs is etched using AZ-1350J photoresist as a mask material using Freon (CC1tFt) or by active ion self-etching.
A short stripe electrode 21 is formed, and its crystal end face is formed into a mirror surface. As a result, laser resonators corresponding to the long stripe electrodes 20 and the short stripe electrodes 21 are formed in the S Nop-GaAB layer 3 as optical waveguides. The reflective mirror surfaces 22 and 23 on the other side of the electrodes 20 and 21 and the reflective mirror surface on one side of the electrode 20 (not shown)
is due to the open plane of the crystal.

5- Since the two laser resonators with different resonator lengths are arranged in parallel sufficiently close to one optical waveguide,
The laser beams generated by these two laser resonators interact electromagnetically through the optical waveguide. Finally, in the gain waveguide laser to which this invention is directed, as mentioned above, optical confinement in the lateral direction parallel to the junction surface is not allowed.
When two laser resonators are arranged in close proximity to each other, they exchange light wave energy with each other, and each laser resonator influences the other laser resonators. As is well known, the content of this interaction is that the laser oscillation of the other laser resonator is encouraged or suppressed and stopped. The strength of this interaction is related to the gap between each laser resonator, the oscillation wavelength, and the t and b phases. As in the semiconductor laser according to the present invention, the resonator length of the laser resonator with the shorter resonator length is set appropriately so as to resonate in a single longitudinal mode, and the length of the two laser resonators is set sufficiently. When placed close enough to allow interaction, both laser resonators resonate strongly when their phases match, resulting in the longer laser resonator resonating with the shorter one.
Although this embodiment has been described using an AzGtAs-based semiconductor laser, the present invention is not limited thereto, and an InGtASP-based semiconductor laser may be used. Further, since it is sufficient to perform etching as long as a reflective mirror surface is obtained, there is no need to perform etching on the crystal end face metal as shown in this embodiment. Furthermore, it goes without saying that the present invention can be applied not only to stripe electrode type semiconductor lasers but also to other gain waveguide type lasers.

As explained in detail above, in the semiconductor laser according to the present invention, a plurality of laser resonators having different cavity lengths are arranged in parallel sufficiently close to one optical waveguide, so that the oscillation mode of each resonator is short. This corresponds to the longitudinal mode of the other laser resonator, and the longitudinal mode of the output light can be easily unified. Furthermore, since a plurality of laser resonators are provided, the output light can be increased in output power, and new applications for the distribution of information processing for video discs and the like can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional semiconductor laser, and FIG. 2 is a schematic diagram showing an embodiment of the present invention. 1......n-G□As substrate 2...
・・・n-AtG□As/ton3・・・・・・・・・p-
GyuA8 (optical waveguide) 4・・・・・・・・・p-AtG
, As layer 5... p-G2LA8 layer 7...
......Lower electrode 20...Long stripe pole 21...Short stripe electrode Patent applicant Tateishi Electric Co., Ltd.

Claims (2)

[Claims] (1) A semiconductor laser in which a band-shaped light emitting region formed by a stripe structure in an optical waveguide in a semiconductor crystal forms a laser resonator with both end faces of the semiconductor crystal being reflective mirror surfaces, and the above-mentioned laser resonator has a different resonator length. A plurality of laser resonators are formed in the optical waveguide, and these laser resonators are arranged in parallel close enough to each other to enable sufficient electromagnetic coupling, and this coupling allows the laser resonator with a long resonator length to be A semiconductor laser characterized in that the oscillation mode is configured to follow the oscillation mode of a laser resonator having a short resonator length. (2) The semiconductor laser according to claim 1, wherein the reflective mirror surface of each of the laser resonators is formed by etching.