JPH02166785A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To perform a high output with high yield by providing a region having a narrow width to obtain a basic lateral mode, and an active region having a region sequentially increasing in width at an angle of its diffraction angle or more. CONSTITUTION:A semiconductor laser is composed of an N-type GaAs substrate 1, an N-type AlxGa1-xAs layer 2, an AlxGa1-yAs layer 3 in which widths are increased at front and rear end faces, a p-type AlxGa1-xAs layer 4, and a P-type GaAs layer 5. The AlyGa1-yAs layer 3 is operated as an active layer, the N-type AlxGa1-xGa layer 2 and the P-type AlxGa1-xAs layer 4 are operated as a clad layer. An active region having a region 6 in which the width of the active layer is narrow width of about 1mum and regions 7, 8 in which the width of the active layer is increased at about 10 degrees of widening angle is provided. Accordingly, since the active layer width of the region 6 is narrow, a lateral mode capable of propagating is only a basic mode, and a light propagated through the region 6 is extended in the boundary between the regions 6 and 7, 8 by a diffraction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser, and particularly to a structure for obtaining a high-output laser with good productivity while maintaining the transverse mode as the fundamental mode.

[Conventional technology]

As a measure to increase the output power of semiconductor lasers, increasing the area of the optical output surface is important and promising. Figure 4 is Applied Physics Letters.
FIG. 2 is a perspective view showing a high-power AlGaAs embedded heterostructure laser described in Letters, Vol. 50, No. 5, page 233. It is characterized by having a flare type optical waveguide in order to obtain high output.

In the figure, 1 is an n-GaAs substrate, 2 is an n-A substrate 1.
The width of Ga, -, As layer 3 expanded at both the front and rear end surfaces (
flare L/ta) Aly Gap-, As layer, 4 is p A1+c Gap-, A3 layer, and 5 is p-GaAs layer.

"y Ga1-, As layer 3 is an active layer, n-, AlXG
al-8AS layer 2 and 9 A l x G a I-
x A 5 layer 4 acts as a ground layer. When biased in the forward direction, the current flows through the A ly Gap-y As layer 3
flows mainly. This is l:l-A IX Gap-,
AsJi4 and nA 1 x Ga + −X A s
This is because the diffusion potential of the pn junction formed with Jig 2 is higher than that of the pn junction via the active layer. Increasing the current leads to oscillation, but by taking advantage of the fact that light is slightly distorted due to the diffraction effect when it exits from a narrow region to a wide region, by increasing the width of the active layer by approximately this diffraction angle. , the width of the light can be gradually expanded to the front and rear end surfaces in the form of almost as-is expansion of the transverse mode in the narrow region. After this, not all of the light reflected by the front and rear end faces returns to the narrow area, but only to a very limited part of the area that is close to the extension of the narrow area, so the dark value of the oscillation is Although it is slightly higher, the width at the end is wider, so
Considering the maximum optical output density as constant, the wider the width, the higher the total output can be expected, and the true output can be achieved.

[Problem to be solved by the invention]

However, in the above example, when actually creating a laser, it is difficult to gradually and smoothly expand the width of the active layer using current processing technology, and it is difficult to gradually and smoothly expand the width of the active layer, which is equal to or more than the wavelength of light (~0.
It is difficult to avoid fine irregularities (5 μm or more). Naturally, when light hits this uneven portion, scattering occurs, causing fluctuations in the transverse mode, often causing unnecessary higher-order mode oscillation. Under conditions where such high-order mode oscillation is allowed, the optical output and current characteristics may be distorted, and the far-field pattern may have many complex irregularities with poor reproducibility, resulting in a significant decrease in manufacturing yield. There was a problem with this.

The present invention has been made to solve the above-mentioned problems, and aims to provide a semiconductor laser that can achieve high output and has a good manufacturing yield.

[Means to solve the problem]

The semiconductor laser according to the present invention has an active active laser having a narrow region for obtaining a fundamental transverse mode, and a region whose width gradually increases from the narrow region at an angle greater than or equal to the diffraction angle in the narrow region. It has an area.

[Effect]

In this invention, in order to obtain high output, the spread angle of the sequentially widened regions is set at an angle greater than the diffraction angle in the narrow region, so the light intensity at the side surface of the optical waveguide is weak, and the light is scattered on the side surface. The impact of
High output can be achieved while maintaining the basic mode with good yield.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a semiconductor laser according to an embodiment of the present invention, and in the figure, the layer configuration is the same as in FIG. 1,
The same reference numerals as in FIG. 1 indicate the same or corresponding parts. Reference numeral 6 indicates a narrow region in which the active layer has a width of approximately 1 μm, and reference numerals 7 and 8 indicate regions in which the width of the active layer widens at a spread angle of approximately 10 degrees.

Next, the effects will be explained.

Since the active layer width in region 6 is as narrow as ~1 μm, the only transverse mode that can propagate in this region is the fundamental mode. Further, at the boundary between the region 6 and the region 7 or 8, the light that has propagated through the region 6 spreads due to a diffraction phenomenon.

This angle is expressed by the relationship λ θ−tan −′ () π ωon (ω is the spot size of the beam, n is the refractive index), and is approximately 4.5 degrees here. Areas 7 and 8
Each acts as an optical amplifier, but even if the angle is extremely wider than the above angle (for example, 45 degrees), there will be less amplified light from region 6 (for example), and current will flow unnecessarily, so in this example, the angle is set to 10 degrees. There is.

In general, if the optical output density at the end face exceeds a certain value, it will lead to end face destruction, so increasing the cross-sectional area of the light exit has been an important issue for increasing the output power of semiconductor lasers. According to
Yield can be improved.

FIG. 2 is a perspective view showing a semiconductor laser according to a second embodiment of the invention. In the second embodiment, compared to the first embodiment, the extension line of regions 7 and 8 (originally, it is the width of the active layer, but since the diagram becomes complicated, the width of the active layer is shown in FIG. The top layer has a shape that reflects the shape of the top layer (the extension line is shown by a broken line), and is characterized by the addition of new areas 9 and 10 that have a constant width wider than the width at the end face of the top layer (the extension line is shown by a broken line).

By adding regions 9 and 10 having a wide constant width in this way, in the first embodiment, the widths of regions 7 and 8 will vary slightly due to deviations in the opening position during device manufacturing, and the irregularity will reduce the commercial value. You can prevent it from falling.

In addition, in the above-mentioned second embodiment, the change in width from region 7 to 9 and from region 8 to 10 is expressed discontinuously, but it is expressed linearly at a gentle angle or gently and continuously with a curve. The width may be widened, and in actual production, this is more advantageous in relation to the plane orientation of the crystal.

In addition, the above 1. In the second embodiment, the shapes are the same in both the front and rear directions, but if high light output is actually required only in the front, regions 8 and 10 may not be provided; It is also good to keep the length to a minimum. The minimum length means that it may be zero.

FIG. 3 is a diagram showing a semiconductor laser according to a third embodiment of the present invention, in which 11 is a pGaAs substrate;
2 is p-Al0.40ao, h As layer, 13 is n-G
aAs1,14 is p-A10. .

G; to, bAs layer, 15 is p-Alo, r Gao,
g As layer, 16 is nA 16,4 Ga o, 6
A 3 layer and 17 are n-GaAs layers. In the third embodiment, the n-GaAs layer 13, which is a current blocking layer, is etched to form the active region shown in the first or second embodiment.
In the case of the second embodiment, ilJ! ! 9.7 and 6)) is formed into a groove having the same shape as n-A10. .

Gao, hAS layer 14 and subsequent layers are grown.

In an example of actual processing, if the width of the bottom of the groove is 1.8 μm, the width W of the active region in that region is 1.2 μm, which is 35 μm.
．． In the region where the thickness was 6 μm, W was 35.0 μm. When the layer thickness of the active layer -A lo, + Gao, + A s layer 15 is 0.07 pm, all higher-order transverse modes are blocked in the region of W = 1.2 μm, and the fundamental mode is In the region where there is no propagation and where W=35 μm, the optical power at which end face destruction occurs is approximately 28 times that of a normal laser, resulting in a high output laser with a maximum optical output of approximately 500 mW and a normal optical output of 140 mW. Of course, the transverse mode of oscillation is W = 35μm
Even though it is wide, the basic transverse mode can be obtained. Also,
In this third embodiment, a current blocking layer (n-GaAs layer 13
), so the above 1. MOC is the most practical method for producing the 0 layer, since it can concentrate the 'g1 flow to the active region over a wider operating range (bias, temperature, etc.) than the second embodiment.
A crystal growth method that can withstand fine processing, such as the VD method or MBE method, is preferable.

In this way, in the third embodiment as well, high output can be achieved, and since the active region with a certain width and a predetermined length is provided near the end face, the yield during manufacturing can be improved. be able to.

〔Effect of the invention〕

As described above, according to the semiconductor laser of the present invention, there is a narrow region for obtaining a fundamental transverse mode, and the width gradually increases from the narrow region at an angle equal to or greater than the diffraction angle in the narrow region. Since the structure includes an active layer having a region with a large area, it is possible to achieve high output with a high yield without impairing fundamental mode oscillation characteristics by allowing unevenness on the side surface that is inevitable during manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a semiconductor laser according to a first embodiment of the invention, FIG. 2 is a perspective view showing a semiconductor laser according to a second embodiment of the invention, and FIG. 3 is a perspective view showing a semiconductor laser according to a second embodiment of the invention. FIG. 4 is a perspective view showing a semiconductor laser according to an embodiment, and FIG. 4 is a perspective view showing a conventional semiconductor laser. 1 is n-GaAs substrate, 2 is n-A Ill Ga, -
. As layer, 3 is AI, Ga, -, A5 layer, 4 is p-A1,
1Ga, -1lAs layer, 5 is a p-GaAs layer, 6 is a narrow active region part, 7 and 8 are active region parts whose width gradually increases, 9.10 is a wide and constant active region part, 11 is p-GaAs substrate, 12 is p-AI 6.4 Ga
6,6 A 3 layers, 13 is n-GaAs layer, 14 beam-A 111.40ao, b As layer, 15 is p-A
16.1 Gao, q As layer, 16 is n-A1.0.
Ga0.6ASJ1% 17 is an n-GaAs layer. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a semiconductor laser having at least two end faces, at least a narrow region provided at one end face portion or at least one location inside thereof through which only the fundamental transverse mode can pass; and a narrow region in the narrow region. What is claimed is: 1. A semiconductor laser comprising: an active region having an active region whose width is gradually increased from the narrow region to the region whose width is gradually widened at an angle greater than the above angle.