JPH02250387A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To readily acquire a high conversion efficiency by providing a specified semiconductor mixed crystal layer inside a resonator having a pair of projection edge faces which are vertical to a lamination surface of a multilayer structure including an active layer which is concerned with light emission. CONSTITUTION:A second higher harmonics generation layer 16 which consists of a semiconductor mixed crystal layer whose energy differential between a first conduction band and a second conduction band at a GAMMA point in a Brillouin zone is approximately the same as that between the first conduction band and a first valence band is provided to an inside of a resonator which consists of a multilayer structure including an active layer 12 which is concerned with light emission, and a pair of edge faces which are vertical to a lamination surface of the multilayer structure. The second harmonic generation layer 16 is formed monolithically in this way of the same substrate together with the multilayer structure including the active layer. Thereby, it is possible to eliminate the necessity of assembly operation and to acquire a semiconductor layer of high combination efficiency and high conversion efficiency readily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser used for high-density optical recording for information processing.

[Conventional technology]

In order to increase the recording density in optical recording using a laser beam with high monochromaticity and high coherency, it is necessary to oscillate light with the shortest possible wavelength. Conventionally, the shortest wavelength limit for room-temperature CW oscillation was 640 nm by the ApGaInP system.
nm has been obtained (Electronics L
et, vol, 23 (1987) P, 1327
).

As a coherent light source even shorter than this, there is one that combines a second harmonic element using a LiNbO3 waveguide using the proton exchange method with a semiconductor laser (Applied Physics vol. 1.56 (1987) P, 1637), 420
nm light is obtained.

[Problem to be solved by the invention]

The laser light emitted from the semiconductor laser is passed through a waveguide type second
When coupled to a harmonic element, extremely high machining precision is required to obtain high conversion efficiency, making it unsuitable for mass production. Furthermore, it is practically difficult to increase the machining accuracy to the extent that a uniform output light is obtained.

[Means to solve the problem]

The present invention is a semiconductor laser in which a monolithically grown semiconductor crystal is used as a second harmonic element without requiring any assembly process, and the first conduction band and the second conduction band at the r point in the Brillouin zone. A second harmonic generation layer consisting of a semiconductor mixed crystal layer in which the energy difference between This structure is characterized by having the resonator inside a resonator consisting of a pair of end faces perpendicular to the laminated surface.

[Effect]

The energy band of the semiconductor mixed crystal forming the second harmonic generation layer (hereinafter referred to as S80 layer) which plays a major role in the semiconductor laser of the present invention is shown in Figure 2, and the absorption spectrum is shown in Figure 3. The present invention will now be described in detail with reference to these figures.

As shown in FIG. 2, the energy band of the SHG layer is such that the energy difference between the second conduction band 3 and the first conduction band 2 is almost equal to the energy difference between the first conduction band 2 and the first valence band 1, and both hν It is. When a semiconductor laser oscillates, the density of photons with energy hν in the SHG layer in the cavity becomes extremely high, so electrons in the first valence band absorb two photons with energy hν and enter the second conduction band. It is resonantly excited to band 3.

Figure 3(a) shows the absorption spectrum of 5HGJI when no laser oscillation is occurring.Laser oscillation begins within the resonator, and as mentioned above, when the two-photon resonance excitation increases sufficiently, the second conduction band 3 and the first Population inversion occurs due to optical excitation between the valence bands 1, and a second harmonic 5 is obtained. The absorption spectrum of the SHG layer at this time is shown in FIG. 3(b). Further, the dependence of the fundamental wave oscillation intensity on the injection current and the dependence of the second harmonic light intensity on the fundamental wave light intensity are shown in FIGS. 4(a) and 4(b), respectively.

In the present invention, since the above-mentioned SHG layer is monolithically formed on the same substrate together with the multilayer structure including the active layer, assembly work is not required, and a semiconductor laser equipped with the SHG layer with high coupling efficiency and conversion efficiency can be easily obtained. It will be done.

〔Example〕

FIG. 1 shows an embodiment of the present invention. The resonator composed of both hexagonal planes has a current injection region 22 and a second harmonic generation region 2.
Consists of 3. The current injection region 22 is a normal double hetero (DH) structure in which an active layer 12 having a forbidden band width narrower than that of the cladding layer is sandwiched between an n-type cladding layer 11 and a p-type cladding layer 13. The population inversion between the first conduction band and the first valence band provides a gain of the fundamental wave hv, and laser oscillation can occur within the resonator. The second harmonic generation region 23 is provided with a second harmonic generation layer 16 made of the semiconductor mixed crystal layer described above, which is two-photon excited by the fundamental wave 4 of energy hν to produce a second harmonic 5 of energy 2hν. occurs. A mixed light of the fundamental wave 4 and the second harmonic 5 is obtained as the laser element output light.

FIG. 5 shows a design example of a semiconductor mixed crystal material that becomes the second harmonic generation layer. The horizontal axis indicates the mixed crystal ratio X of the ternary mixed crystal material. Both ends x=0. x=1 are binary compound semiconductors AC and B, respectively
It is C. The vertical axis indicates energy based on the first valence band energy.

In the figure, when the mixed crystal ratio “yc=xc”, EC2EC1=E01
-Ev holds and is suitable for the second harmonic generation layer.

〔Effect of the invention〕

According to the present invention, temperature C
A semiconductor laser capable of W operation can be obtained.

Since the wavelength of the second harmonic is 1/2 that of the fundamental wave, when used as a light source for optical recording and reading, it is possible to read information with a recording density four times higher.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the band structure of the second harmonic generation layer, Fig. 3 is a diagram showing the absorption spectrum of the second harmonic generation layer, and Fig. 4 is a diagram showing an absorption spectrum of the second harmonic generation layer. 5 is a diagram showing the fundamental wave light intensity and the second harmonic light intensity, and FIG. 5 is a diagram showing a design example of the semiconductor mixed crystal material that becomes the second harmonic generation layer. In the figure, 1 is the first valence band, 2 is the first conduction band, 3 is the second conduction band, 4 is the fundamental wave, 5 is the second harmonic, 12 is the active layer, 1
6 indicates a second harmonic generation layer.

Claims (1)

[Claims] A first conduction band and a second conduction band at the Γ point in the Brillouin zone are formed in a resonator consisting of a multilayer structure including an active layer that participates in light emission and a pair of emission end faces perpendicular to the laminated surface of this multilayer structure. A semiconductor laser comprising a semiconductor mixed crystal layer in which the energy difference between the first conduction band and the first valence band is approximately equal to the energy difference between the first conduction band and the first valence band.