JP2798720B2 - Semiconductor laser array - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor laser array used for optical information processing or laser processing.

[Conventional technology]

Generally, in a semiconductor laser, when the drive current is increased to increase the optical output, the pn junction generates heat, and the optical output is thermally saturated due to an increase in the threshold current density and a decrease in the external differential quantum efficiency. The maximum light output of each semiconductor laser is determined by this thermal saturation or optical end face breakdown accompanying the increase in light output.

With the expansion of the application range of laser light emitted from a semiconductor laser, the demand for high-power laser light is increasing. As a means for obtaining high-power laser light, a plurality of semiconductor lasers having a waveguide are arranged in parallel. Semiconductor laser array (K. Hamada et al. Solid-State Electronics)
Vol. 30, No. 1 pp. 33-37, 1987). Such semiconductor laser arrays include two types: a phase-locked type in which the laser light from each semiconductor laser has the same phase, and a non-phase-locked type in which the laser light from each semiconductor laser has the same phase. There are types.

[Problems to be solved by the invention]

In the above-described phase-locked semiconductor laser array, the distance between adjacent waveguides needs to be set to about 5 μm or less in order for the laser light generated in each waveguide to be phase-locked.
However, in such a configuration, since the semiconductor lasers are closely arranged side by side, the semiconductor lasers are susceptible to each other with respect to heat generated from the semiconductor lasers, and the temperature rise of the pn junction is large. Is likely to occur, and a high output laser beam cannot be obtained.

In order to prevent the influence of heat generated from each other between the semiconductor lasers, each semiconductor laser in the array must be tens of μm.
A configuration in which the semiconductor lasers are separated by m or more (a non-phase-locked semiconductor laser array in which phase synchronization cannot be applied between the semiconductor lasers) may be employed. However, in this configuration, since the adjacent semiconductor lasers are too far apart, there is a drawback that the beam light emitted from each semiconductor laser cannot be focused on one point using a lens or the like.

The present invention has been made in view of such circumstances, and the effect of heat generated from each semiconductor laser can be reduced by shortening the distance between the waveguides near the end face and increasing the distance between the waveguides in the center, and furthermore, the lens and the like can be reduced. It is an object of the present invention to provide a semiconductor laser array capable of condensing beam light from each semiconductor laser at one point using the same.

[Means for solving the problem]

The semiconductor laser array according to the present invention is a semiconductor laser array including a laser chip having a plurality of waveguides formed in parallel, wherein the laser chip has a distance between adjacent waveguides equal to a first distance. A first region near the end face of the first and second central regions where the distance between the adjacent waveguides increases from the one end surface toward the other end surface, and the distance between the adjacent waveguides is the first region. A third region near the other end face that is a second distance wider than the first region, wherein the waveguides in the first and third regions are more laser than the waveguides in the second region. It is characterized in that it extends in a direction perpendicular to the chip end face.

[Action]

In the semiconductor laser array of the present invention, the distance between adjacent waveguides is small near the end face, and each laser beam emitted from the end face via each waveguide is condensed to one point by a lens or the like. In the central portion, the distance between adjacent waveguides is large, the influence of heat generated from each semiconductor laser on the adjacent semiconductor lasers is reduced, and the optical output is hardly thermally saturated. Also, since the waveguide is orthogonal to the laser chip end face, the laser light propagating in the waveguide is efficiently reflected by the laser chip end face, and the light output can be increased.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments.

FIG. 1 is a plan view of a semiconductor laser array according to the present invention,
FIG. 2 is a partial sectional view taken along line II-II of FIG.

In FIG. 1, reference numeral 10 denotes a laser chip, and the length of the laser chip 10 in plan view (resonance length) between both end surfaces 11 and 12 is shown.
Has a rectangular shape with a width of 750 μm and a width of 600 μm, and a total of three waveguides 1 are formed between both end faces 11 and 12 in correspondence with each semiconductor laser. Note that the reflectance of the left end face 11 in the figure is 90.
% And the reflectance of the right end surface 12 is 8%.

Here, the device structure of this embodiment will be described with reference to FIG. In FIG. 2, reference numeral 2 denotes an n-GaAs substrate (Si-doped, n = 2 × 10 ¹⁸ cm ⁻³ ).
_0.58 Al _0.42 As cladding layer (Se-doped, n = 5 × 10 ¹⁸ cm ^-3 ,
Ga _0.58 Al _0.42 As active layer (non-doped, film thickness 0.07 μm) 4, p-Ga _0.58 Al _0.42 As clad layer (Zn doped, p = 2 × 10 ¹⁸ cm ⁻³ , film thickness 1.5) μm) 5, p-Ga
As cap layer (Zn doped, p = 1 × 10 ¹⁹ cm ^-3 , thickness 0.5μ)
m) 6 are laminated in this order. The p-cladding layer 5 and the cap layer 6 are removed in a reverse mesa shape at a predetermined pitch, and an n-GaAs block layer (Se-doped, n = 5 × 10 ¹⁸ cm ⁻³ , film thickness 1.0) μm) 7 is formed. In this embodiment, each waveguide 1 forms a ridge-shaped stripe. In order to obtain a stable fundamental transverse mode in each waveguide 1, the active layer 4 extends from the lower end of the block layer 7.
The distance (t) to the upper surface was set to t = 0.1 to 0.2 μm, and the width (W) of the waveguide was set to W = 3 to 4 μm.

The juxtaposed formation pattern of each waveguide 1 is different in three regions in the longitudinal direction of the laser chip 10. End face 11
In the nearby region A, the interval between the adjacent waveguides 1 and 1 is narrow, and in the central region B, the waveguide 1 radially expands,
The interval between the adjacent waveguides 1 and 1 is gradually widening, and in the region C near the end face 12, the interval between the adjacent waveguides 1 and 1 is wide. The waveguide 1 extends in a direction substantially perpendicular to the end face 11 in the region A, and extends in a direction substantially perpendicular to the end face 12 in the region C. The specific shape of the ridge-shaped stripe of the waveguide 1 is as follows.

The length L ₁ = 50 [mu] m area A, length L ₂ = 550 .mu.m region B, the length L ₃ = 150 [mu] m area C, between the waveguides in the region A distance D ₁ = 3 [mu] m, between the waveguides in the region C the distance D ₂ = 100 μm Here, the bent portion of the waveguide 1 (the boundary between the regions A and B and B and C)
Is preferably formed in an arc shape in order to reduce radiation loss, and the radius of curvature of this arc is preferably at least 1 to 2 mm or more. In order to improve the heat radiation from the waveguides 1 and 1 located at both ends, the distance (D _{3 in} FIG. 1) from the waveguides 1 at both ends to the side surface in the region C is as long as possible (150 μm).
Degree). Incidentally, if the distance D ₁ of the next matching waveguide at the end face 11 near to 8μm or less, condensing at one point the laser beam from the waveguide by a lens or the like.

Next, comparison of current-light output characteristics between the present invention and the conventional example will be described. FIG. 3 is a graph showing the characteristics of both examples. FIG. 3 (a) shows the characteristics in the case of the above-described present invention example shown in FIGS. 1 and 2, and FIG. 3 (b) shows the characteristics in FIG. The characteristics in the case of such a conventional example are shown. FIG. 4 is a plan view of a conventional example used here. In a laser chip 20 having a distance between end faces of 750 μm, three waveguides 21 are formed in parallel between both end faces, and adjacent waveguides are formed. The interval between the wave paths 21 and 21 is the same (6 μm) in any region.

As understood from FIG. 3, in the conventional example (b), the light output is saturated at 190 mW. On the other hand, in the example (a) of the present invention, since the oscillation is shifted between the laser at the center and the laser at both ends, the curve showing the current-light output characteristic is bent, but the light output is not saturated up to 240 mW. . As described above, in the semiconductor laser array of the present invention, the light output is less likely to be thermally saturated than in the conventional case.

In the semiconductor laser array of the present invention, since the distance between the adjacent waveguides is large at the center as described above, the influence of heat emitted from each semiconductor laser can be reduced, and the light output can be increased. Further, since the distance between adjacent waveguides is reduced near the end face, laser light from each semiconductor laser can be focused on one point using a lens or the like.

〔The invention's effect〕

As described in detail above, in the semiconductor laser array of the present invention,
The laser chip includes a first region near one end face where the distance between the adjacent waveguides is the first distance, and a distance between the adjacent waveguides from the one end face toward the other end face. A central second region that extends, and a third region near the other end face where the distance between adjacent waveguides is the second distance that is greater than the first distance, and
Since the waveguide in the third region extends in a direction perpendicular to the end face of the laser chip more than the waveguide in the second region, light is emitted from each semiconductor laser using a lens or the like. The laser light can be focused at one point, and the light output is less likely to be thermally saturated, and the laser light is efficiently reflected at the end face of the laser chip, so that a higher output of the laser light can be achieved. Therefore, the present invention has excellent effects such as further expanding the range of application as a light source in optical information processing and laser beam processing.

[Brief description of the drawings]

1 is a plan view of a semiconductor laser array according to the present invention, FIG. 2 is a partial cross-sectional view taken along line II-II of FIG. 1, FIG. 3 is a graph showing current-light output characteristics, and FIG. 3 is a plan view of the semiconductor laser array of FIG. 1 ... waveguide, 2 ... substrate, 3 ... n-cladding layer, 4
... active layer, 5 ... p-clad layer, 6 ... cap layer, 7 ... block layer, 10 ... laser chip, 11, 12 ...
…End face

Claims (1)

(57) [Claims] 1. A semiconductor laser array comprising a laser chip having a plurality of waveguides formed side by side, wherein the laser chip has an interval between adjacent waveguides of a first type.
A first region in the vicinity of one end face, which is a distance between the first and second end faces, and a central second area in which the distance between the adjacent waveguides increases from the one end face toward the other end face; And a third area near the other end face, wherein the distance between the first and second distances is a second distance wider than the first distance.
The semiconductor laser array according to claim 1, wherein the waveguide in the third region extends in a direction orthogonal to the end face of the laser chip than the waveguide in the second region.