JPS62266888A - Semiconductor laser array - Google Patents

Abstract

PURPOSE:To reduce optical density at an end surface part, to suppress the deterioration at the end surface of a laser device and to obtain the laser device characterized by high output power and a long life, by making the thickness of an active layers at the end surface parts of both resonators of a laser crystal thinner than the inside of the crystal. CONSTITUTION:On a P-type GaAs substrate 1, a mesa 9 is formed by etching. Then the mesa is buried by a liquid phase epitaxy method, and the first growing is performed so as to flatten the surface. A ridge 11 and three grooves 10 are formed by etching. At this time, the width of the ridge 11 is made narrow in the vicinity of the end surface. The second phase epitaxy is performed on the substrate, and a multilayer structure is grown. At this time, the narrower the width of the ridge, the slower the growing speed on the ridge. Therefore an active layer becomes thin at the end surface part where the width of the ridge 11 is narrow in comparison with the inside of the crystal. When the active layer is thin, confinement of light becomes poor, and the diameter of the laser light beam becomes large in the vicinity of the end surface. Therefore the optical density can be decreased. As a result, the device can withstand up to high output power.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor laser array device used as a high-power infrared laser light source for recording and erasing optical discs, medical purposes, and other purposes.

Conventional Technology In recent years, semiconductor laser array devices have come into the spotlight as central devices in the optical industry, for reading signals on optical disks such as CDs, as light sources for laser beam printers, and for optical communications. . In these optical information devices, the requirement for laser optical output is 10 to 20 m.
Most were below W. However, the demand for semiconductor laser array devices with high output (20 mW or more) for use in recording and erasing optical disks, speeding up printers, and medical equipment has been increasing rapidly in recent years.

There are two obstacles to increasing the output power of semiconductor laser devices. One of them is that when the output is increased, the mode of the optical electric field propagating within the crystal tends to shift from the fundamental mode to the higher-order mode as the optical density within the laser crystal increases. When oscillating in a higher-order mode, the intensity distribution of the laser beam emitted from the end face of the crystal does not have a single peak, but instead has multiple peaks, which poses a major practical problem. This problem,
This problem can be solved by reducing the thickness of the oscillation region (active layer) within the laser crystal. And the so-called BuriθdTwin
Rid(e 5ubstrata L/-) The current value is 20% by making the active layer thinner and improving the current injection efficiency.
Continuous oscillation output of 0 mW or more is obtained. (IEICE technical research report ED84-94 (1984)) No. 2
The point is that as the optical density increases at the laser crystal end face, deterioration progresses near the end face, shortening the life of the laser device. At the laser end face, heat dissipates poorly compared to inside the crystal, and locally in the oscillation region near the end face, 20
It has been reported by Todoroki et al. that the temperature can exceed 0'C. (Journal Op Applied Physics, 6
8゜1) 1124 (1985)) This local heat generation is
The generation and proliferation of dislocations within the crystal is promoted, and the dislocations become non-emissive centers that absorb laser light and generate further heat, repeating a vicious cycle (thermal runaway), which significantly shortens the life.

Problems to be Solved by the Invention The present invention reduces the optical density of the laser beam at the crystal end face, reduces the generation of heat at the end face, and prevents damage to the end face due to heat and deterioration of reliability due to thermal runaway during laser operation. The purpose of the present invention is to provide a semiconductor laser array device with a long service life.

Means for Solving the Problems In order to solve the above problems, in the semiconductor laser array device of the present invention, the thickness of the active layer at both cavity end faces of the laser crystal is made thinner than the thickness inside the crystal.

Effect: With this configuration, the beam diameter of the laser beam at the end face becomes large, and the light density decreases. This effect suppresses deterioration at the laser end face, making it possible to realize a laser device with high output and long life.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIGS. 1a and 1b show cross sections of a semiconductor laser array device in an embodiment of the present invention. Figure 1 shows a cross section near the end face, and Figure 1 shows a cross section inside the end face. The n-type GaAs layer 2 on the p-type G&M S substrate 1 is for blocking current. There is a mesa 9 on the GaAs substrate 1, and the groove 1o provided in the GaAs current blocking layer 2 or the mesa 9
, and current is injected into the active layer 4 from the groove 1°. The ridge 11 of the block layer 2 is provided to facilitate control of the thickness of the active layer 4 during liquid phase epitaxial growth. That is, the crystal growth rate on the ridge 11 is slow in liquid phase growth, which is utilized. Here Ridge 11
The width is smaller near the end face than inside.

FIG. 2 shows a part of the manufacturing process of the semiconductor laser array of the present invention. A mesa 9 is formed on the p-type G&M S substrate 1 by etching. The length of the mesa is 200 μm, the height is 3 μm, and the width is 30 μm.

The resonator end faces are formed by opening the valve at the front and rear parts of the mesa. (FIG. 2a) Next, the first growth is performed by liquid phase epitaxial growth to completely fill the mesa and make the surface flat. (Figure 2b) n-type GaA on mesa
The thickness of the s-layer 2 is 1.0 μm. A ridge 11 and three grooves 10 are formed by etching. (Figure 2C)
The depth of the groove is 1.5 μm, the width of the groove is 2 μm, and the groove spacing is 3 μm.
shall be.

At this time, the width of the ridge 11 is made narrower near the end face. That is, it is 100 μm inside the crystal and 40 μm near the end face. Then, a second liquid phase epitaxial growth is performed on the substrate shown in FIG. 2C to grow the multilayer structure already shown in FIG. At this time, the growth rate on the ridge is
As the width of the ridge becomes narrower, the speed becomes slower, so the active layer becomes thinner at the end face portion where the width of the ridge 11 is narrower than inside the crystal.

If the active layer is thin, light confinement will be poor, and the beam diameter of the laser beam will become large near the end face. Therefore, the light density can be reduced. As a result, it can withstand high output. Next, the electrodes 7 and 8 are deposited, and then the valve is opened to create a resonator end face.

FIG. 3 shows the current vs. optical output characteristics of the semiconductor laser array device of the present invention and the conventional semiconductor laser array device. A significant increase in saturation power is observed due to the decrease in optical density at the end face and the suppression of heat generation. FIG. 4 shows the change over time of the operating current in constant first output drive. Although conventional laser array devices have a short lifespan at high output, the device according to the present invention has a sufficiently long lifespan for practical use.

Effects of the Invention As described above, the present invention can significantly extend the life of a semiconductor laser array device by thinning the active layer at the end face portion, and its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a semiconductor laser array device according to an embodiment of the present invention, FIG. 2 is a perspective view showing a part of the manufacturing process, and FIG. 3 is a characteristic showing the relationship between current and optical output of the semiconductor laser array device. 4 are characteristic diagrams showing changes over time in the operating current of the semiconductor laser array device when driven with a constant optical output. 1...p-type GaAs substrate, 2...n-type GaAs block layer, 3...p-type Ga,
, A/yAs cladding layer, 4-...GalzAgxA
s active layer, 5...n-type Ga1. A/yAs cladding layer, 6... n-type GaAs layer, 7.8...
...Electrode, 9...Mesa, 10...Groove, 11...Ridge. Name of agent: Patent attorney Toshio Nakao and 1 other person'-
-P';-Gcb 5 bases 2--flW OnAδ face]

Claims (1)

[Claims] A layer of a conductivity type opposite to the one conductivity type is formed on the surface of a semiconductor substrate of one conductivity type having striped protrusions, and a plurality of layers have a depth reaching the protrusion from the surface of the layer of the opposite conductivity type. A striped groove is formed, and two ridges parallel to each other are formed on both sides of the two outermost grooves so that the width becomes narrow near both end surfaces of the substrate, and the ridge is A semiconductor laser array device characterized in that each layer including an active layer is formed on a substrate having a semiconductor laser array.