JPS62242382A - Protective device of end face of semiconductor laser - Google Patents

Abstract

PURPOSE:To attain the effect of protection of the end face of a semiconductor laser chip without the need to form an electricity-transmitting substance on the end face by evaporation, by forming an electrode for current injection on the upper surface of the central part of the chip except the vicinity of the end face thereof, and by providing electrodes for voltage impression on the upper surface in the vicinity of the end face with an insulating film interposed between. CONSTITUTION:A common electrode 5 is formed on the lower surface of a laser chip 10, an electrode 6 for current injection in the central part of the upper surface thereof, and electrodes 8 for voltage impression on the upper surface thereof in the vicinity of the opposite end faces to operate as resonator faces with insulating films 7 inter posed between, respectively. The electrode 6 for current injection is not formed in the vicinity of the end faces, and an active layer 3 in the vicinity of the end faces operates exclusively as an optical waveguide. When a voltage is impressed thereon from the electrodes 8, the refractive index of a multiplex quantum well portion (of the active layer 3) lowers, and as the result, the coefficient of optical confinement becomes small. Therefore, a light in the active layer 3 leaks out into clad layers 4 and 2 and consequently a photon density in the vicinity of the end faces lowers.

Description

DETAILED DESCRIPTION OF THE INVENTION Summary of the Invention End face protection is an important issue in increasing the output of semiconductor lasers. Conventionally, the common method was to attach a dielectric film to the end face. In this invention, in a semiconductor laser having a multi-quantum well structure as an active layer, an electric field is applied only near the end facets by utilizing the electric field dependence of the refractive index, which is a unique property of the semiconductor laser, and light confinement in that part is weakened. By leaking light into the cladding layer, we lowered the photon density and protected the end face.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for protecting an emission end face of a semiconductor laser having a multi-quantum well structure as an active layer.

Prior Art and Its Problems The electric field intensity of laser oscillated light is at its maximum at the end face of a semiconductor laser, which corresponds to the resonant surface, so it is susceptible to thermal breakdown and oxidation. For this reason, it is necessary to consider protection of the end faces, especially when aiming at high output.

A conventional method for protecting the end face of a semiconductor laser is to deposit a dielectric material on the end face. This makes the oscillation wavelength of -the λ
, a dielectric for that wavelength (e.g. AJ O,5i
3N4, etc.), and when n is the refractive index of 2, this dielectric material should be placed at the end face where the electric field strength of light would normally be maximum at λ/ (4n).
It protects the semiconductor end face by lowering the electric field strength at the semiconductor end face without changing the laser characteristics. However, in this conventional method, the dielectric material is deposited after the laser end face is formed, which requires multiple steps, and the end face is easily damaged during dielectric deposition.
There were problems such as difficulty in precisely controlling the film thickness.

SUMMARY OF THE INVENTION OBJECTS OF THE INVENTION An object of the present invention is to provide an end face protection device for a conductor laser that is easy to manufacture.

Structure and Effects of the Invention The present invention provides a semiconductor laser having a multi-quantum well structure as an active layer, in which a current injection electrode is formed on the upper surface of the central part of the semiconductor laser chip except for the vicinity of the end facet, and the current injection electrode is formed on the top surface of the central part of the semiconductor laser chip except for the vicinity of the end facet. ``Secondly, a voltage applying electrode is provided via an insulating film.

Since the current injection electrode is not provided near the end face of the semiconductor laser, the area near the end face becomes a current non-injection region. When an electric field is applied to a multiple quantum well structure, the refractive index decreases. In this invention, the refractive index of the active layer is lowered by applying a voltage from the voltage applying electrode near the end face of the semiconductor laser.

This weakens the light confinement and reduces the light intensity at the end face, thereby protecting the end face.

Therefore, it is not necessary to form a dielectric film on the end face as in the conventional case, and the amount of time required for forming the dielectric is reduced.

In addition to solving all the above-mentioned problems, according to the present invention, manufacturing is easy because it is only necessary to provide a voltage applying electrode on the upper surface near the end face A of the semiconductor laser chip via an insulating layer. It is.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the embodiment parallel to the resonator.

In these figures, the semiconductor laser chip IO is connected to a substrate 1. Lower cladding layer 2. It is composed of an active layer 3 having a multi-quantum well structure and a two-part cladding layer 4.

A common electrode 5 is provided on the lower surface of this laser chip 10, a current injection (laser drive) electrode 6 is provided in the center of the upper surface, and a voltage is applied via an insulating film 7 to two surfaces near both end surfaces that become the resonator surfaces. Application electrodes 8 are formed respectively.

Since the current injection electrode 6 is not formed near the end face of the laser chip 10 and no current is injected, the active layer 3 near the end face mostly works as an optical waveguide. When a voltage is applied from the electrode 8 here, as is well known, the refractive index of the multiple quantum well portion (active layer 3) decreases mainly due to potential deformation of the barrier layer. As a result, the difference in refractive index between the active layer 3 and the upper and lower cladding layers 4, 2 becomes smaller, and the light confinement coefficient becomes smaller, so that light from the active layer 3 leaks to the cladding layer 4.2.

As a result, the photon density near the end face decreases.

In particular, there is no need to deposit a conductive material on the end face.

The effect of edge protection can be obtained. In addition, the light is transmitted to the cladding layer 4.
By leaking into the second laser beam, the output aperture of the single-oscillation laser beam is substantially increased, and the spread of the output light beam is also reduced.

Note that since there is almost no change in the reflectance of the end face of the laser bone chip 10, it goes without saying that the end face continues to function as a resonant surface.

This invention is applicable to all semiconductor lasers having a quantum well structure in the active layer, regardless of laser structure or crystal material.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, with the first being a perspective view and the second being a perspective view.
The figure is a longitudinal sectional view. 3... Active layer, 5... Common electrode, 6... Current injection electrode, 7... Insulating film, 8... Voltage application electrode. that's all

Claims (1)

[Claims] In a semiconductor laser having a multi-quantum well structure as an active layer, a current injection electrode is formed on the upper surface of the central part of the semiconductor laser chip except for the vicinity of the end surface, and a voltage application electrode is formed on the upper surface near the end surface via an insulating film. An end face protection device for a semiconductor laser which protects the end face by providing a current non-injection region near the end face and applying a voltage to the region from the voltage applying electrode to weaken optical confinement and weaken the light intensity.