JPH05226776A - Laser diode array - Google Patents

Abstract

PURPOSE:To suppress temperature increase and prevent laser performance deterioration by providing a wave conducting path which does not perform laser beam oscillation adjacent to an activating layer in the same shape as the activating layer and arranging the wave conducting path and the activating layer so as not to be next to each other in the adjacent laser diode. CONSTITUTION:The size of a wave conducting path 11 arranged adjacent to an activating layer 2 is the same as that of the activating layer 2. A half of the area of the activating layer 2 of the conventional LD array is replaced by the wave conducting path 11 and the activating layer 2 and the wave conducting path 11 are arranged so as not to be next to each other in the adjacent LD. As for the structure of the LD, for example, the activating layer 2 is constituted of a multi-quantum well and impurity diffusion is performed on a part equivalent to the wave conducting path 11 in the activating layer 2 or thermally disordering is performed on the part using fine laser beams, etc., and the wave conducting path is formed in the activating layer 2. Since the wave conducting path 11 is an inactive area, heat is not generated by the current concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode array, and more particularly to a laser diode array in which a plurality of laser diodes are arranged on the same chip with improved thermal characteristics.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a chip arrangement of a conventional laser diode (hereinafter abbreviated as LD) array, in which 1 is a chip and 2 are a plurality of chips formed on the chip 1. This is the active layer of the LD, and carriers are confined in the active layer 2, where the carriers recombine to generate laser light. Reference numerals 3a and 3b denote reflecting mirrors provided in parallel to each other, and form a resonator that oscillates the laser light by reflecting the laser light generated in the active layer 2 between the reflecting mirrors 3a and 3b. There is. 4 is a reflector 3
Represents the laser light (pitch L) that is output to the outside of each LD after passing through. In the conventional LD array shown in FIG. 3, a desired number of LDs having the same structure are arranged in a line, whereby a desired number of laser beams having a pitch L can be output.

FIG. 4 shows each LD in a conventional LD array.
4 is a diagram showing a sectional structure of FIG. 3, in which a part of the AB cross section shown in FIG. 3 is enlarged and shown, and the same reference numerals as those in FIG. 3 indicate the same or corresponding portions. In FIG. 4, 5
Is a substrate of the LD, and 6 is a current blocking layer formed on both sides of the active layer 2, and performs current confinement in order to efficiently flow a current to the active layer 2. Reference numeral 7 is a contact layer, 8 is an electrode provided on the contact layer 7, 9 is a common electrode provided on the substrate 5 side and provided under the substrate 5 in common with an adjacent LD, 10
Is an element isolation groove for separating each LD in the LD array into individual LDs.

Next, the operation will be described. When a forward voltage is applied between the electrode 8 and the common electrode 9, a current flows into the active layer 2, and the current is concentrated in the active layer 2 to confine carriers and light, thereby forming a resonator. The laser light is reflected and oscillated between them, and finally passes through the reflecting mirror 3b to emit the laser light to the outside of the LD. Here, the electrode 8 and the common electrode 9 are electrodes for supplying a current, and the generated current passes through the waveguide and the active layer 2
Reach At this time, the current blocking layer 6 serves as an insulating layer for efficiently concentrating the current to the active layer 2, so that the laser output of the LD can be secured even with a small input current, and the laser output characteristic of the LD can be secured. It is possible to improve.

As described above, when the LD operates, the current is concentrated in the vicinity of the active layer 2, so that the amount of heat generated is greatest around the active layer 2 and is also a high temperature portion. Fig. 5 shows a single L
It is a figure which shows an example of the laser output characteristic with respect to the input current of D, and the electric current (mA) input into LD is taken on the horizontal axis, and the laser output (mW) is taken on the vertical axis. In FIG. 5, T indicates the ambient temperature of the active layer 2, and t _H and t _L have a relationship of t _H > t _L. The curves indicated by T = t _H and T = t _L show the relationship between the input current and the laser output when the ambient temperature of the active layer 2 is high and low, respectively. As shown in the figure, when the temperature T around the active layer 2 becomes high (t _H ), the laser output becomes worse than when the temperature T around the active layer 2 is low (t _L ). That is, the higher the ambient temperature of the active layer 2, the worse the output characteristics of the laser.

In the conventional LD, the current block layer 6 is provided as described above so that the current is concentrated in the active layer 2 to secure the laser output. However, the larger the laser output is, the more the laser oscillation occurs. As a result, the amount of heat generated is increased, and the ambient temperature of the active layer 2 is increased. Therefore, by attaching a heat sink or the like to the common electrode 9 side, the heat generated by the laser oscillation is released from the heat sink to lower the temperature of the active layer 2.

[0007]

Since the conventional laser diode array is constructed as described above, it is necessary to lower the temperature around the active layer 2 as much as possible in order to secure the laser output. Although a heat sink or the like is attached to the side, if the heat resistance of the substrate 5 which is the heat diffusion layer provided between the active layer 2 which is the heat source and the common electrode 9 which is the heat radiation surface is large, heat radiation is performed. However, there was a problem in that it was difficult to lower the temperature. On the other hand, in order to improve the heat dissipation efficiency of the substrate 5 which is a heat diffusion layer, the thickness of the substrate 5 is made as thin as possible to reduce the thermal resistance, and the thermal diffusion is smoothly performed to secure the laser output. However, due to the strength of the substrate 5, the thinness is usually limited to about 100 μm, and it is difficult to improve the laser output characteristics of the semiconductor laser device. ..

In addition, the LDs adjacent to each other in the LD array
The distance between them, that is, the pitch L between the laser output lights, is required to be as fine as about 50 to 100 μm in accordance with the recent increase in device density, so that the active layer 2 which is a heat source is considerably close to each other. This means that temperature rises and adjacent LDs
There is a problem in that the laser characteristics of the semiconductor laser device are deteriorated because the semiconductor laser device is more easily affected by thermal interference between them.

The present invention has been made to solve the above problems, and in each LD of the LD array,
An object of the present invention is to obtain a laser diode array capable of preventing a decrease in laser performance by suppressing a temperature rise by lowering a thermal resistance of a substrate between an active layer which is a heat source and a common electrode which is a cooling surface. ..

[0010]

A laser diode array according to the present invention has a waveguide portion adjacent to the active layer portion, which has the same shape as the active layer portion and does not oscillate laser light. The waveguide portion and the active layer portion are arranged so as not to be adjacent to each other between the laser diodes.

[0011]

The laser diode array according to the present invention is
Since the active layer portion and the waveguide portion continuously arranged in the active layer portion are arranged so as not to be adjacent to each other between the adjacent LDs, the active layer portion which is a heat source should be dispersedly arranged. , Which can suppress the temperature rise,
Further, by disposing the heat sources in a distributed manner, thermal interference is also reduced, so that it is possible to prevent a temperature rise around the active layer and prevent deterioration of laser characteristics. Furthermore, L
It is possible to reduce the thermal resistance while maintaining the desired pitch L without changing the pitch L of D.

Further, the waveguide portion and the active layer portion have the same shape,
In the case of dimensions, the size of the entire laser diode is doubled from the conventional size, and the area of the heat dissipation surface is increased to reduce the thermal resistance without lowering the laser output.
The heat generated in the active layer can be quickly diffused.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a chip arrangement of a laser diode (hereinafter referred to as LD) array according to an embodiment of the present invention. In the figure, the same symbols as those in FIG. 3 indicate the same or corresponding portions. In FIG. 1, reference numeral 11 denotes a waveguide arranged adjacent to the active layer 2, and its size is the same as that of the active layer 2.
As shown in FIG. 1, in the LD array of the present invention, the conventional L array is used.
Half of the area of the active layer 2 of the D array is replaced with the waveguide 11, and between the adjacent LDs, the active layer 2 and the waveguide 1 are arranged.
1 and 1 are arranged so as not to be adjacent to each other. 2 is a diagram showing a sectional structure of each LD in an LD array according to an embodiment of the present invention. Here, a part of the CD section shown in FIG. 1 is shown in an enlarged manner.
The same reference numerals as those in FIGS. 1 and 4 denote the same or corresponding portions.

In this LD structure, for example, the active layer 2 is formed by MQ.
It is composed of W (Multi Quantum Well), and then impurities are diffused in a portion corresponding to the waveguide 11 in the active layer 2, or the same portion is thermally disordered by a thin laser beam or the like. The waveguide 11 can be formed in the active layer 2 by a method such as (disordering).

The waveguide 11 formed as described above
Is a waveguide that is transparent to the output laser light, that is, a waveguide that does not absorb the laser light. Since the waveguide 11 is an inactive region, even if a current flows through the waveguide 11, it does not function as the active layer 2 and heat is not generated due to current concentration.

As described above, in the LD array, the active layer 2
Adjacent to the active layer 2 and having the same shape and size as the waveguide 1
1 and by disposing the active layer 2 and the waveguide 11 so as not to be adjacent to each other between adjacent LDs, the active layers 2 are spatially close to each other between adjacent two or three LDs. However, in operation, between the LDs that are vertically adjacent to each other,
Alternatively, the LDs that are diagonally adjacent to each other are separated by the waveguide 11 that is an inactive region, and as a result, the heat sources are dispersedly arranged, so that the temperature rise can be suppressed. In addition, since the heat interference is reduced by disposing the heat sources in a distributed manner, it is possible to prevent the temperature rise around the active layer 2 and prevent the deterioration of the laser characteristics. Furthermore, the active layers 2 can be dispersedly arranged without changing the pitch L of the LDs, and the thermal resistance can be reduced while keeping the desired pitch L.

On the other hand, when the waveguide 11 is formed in the active layer 2 by a method such as impurity diffusion or disordering as described above, the active region for generating laser light is reduced by the amount of the waveguide, that is, Although the laser output is reduced, if the active layer 2 is made twice as large as the active layer 2 in the conventional laser diode array and the waveguide 11 is formed in the half of the active layer 2, that is, the LD array. If the overall size of each LD constituting the LD is doubled from the conventional one, the active region can be maintained at the same size as the conventional one, so that the laser output characteristic becomes almost the same as the conventional one, and the waveguide 11 is By increasing the chip area by the amount provided, the area on the side of the electrode 9 which is the heat dissipation surface is increased, so that the thermal resistance is reduced accordingly and the active layer 2 is reduced. Can diffuse quickly the heat generated, it is possible to prevent a decrease in laser characteristics.

[0018]

As described above, according to the laser diode array of the present invention, a waveguide which is continuous with the active layer and has the same shape and size as the active layer and which does not oscillate laser light is provided. Since the active layer and the waveguide are arranged so as not to be adjacent to each other between the adjacent LDs, in operation, the active layer, which is the heat source, is separated by the waveguide, which is the inactive region. The rise can be suppressed, and the thermal interference can be reduced by disposing the heat sources in a distributed manner. Therefore, the temperature rise around the active layer can be prevented and the laser characteristics can be prevented from being deteriorated. Further, since the active layers can be dispersed and arranged without changing the pitch L of the LDs, there is an effect that the thermal resistance can be reduced with the desired pitch L.

Further, according to the laser diode array of the present invention, the size of the LD as a whole is doubled by forming the waveguide with the same shape and size as the conventional active layer. The effect of increasing the area of the heat radiating surface to reduce the thermal resistance and quickly diffusing the heat generated in the active layer without lowering the laser output and preventing the deterioration of the laser characteristics is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a chip arrangement of a laser diode array according to an embodiment of the present invention.

FIG. 2 is a cross-sectional structural view showing an enlarged part of a cross section of a laser diode of the laser diode array shown in FIG.

FIG. 3 is a diagram showing a chip layout of a conventional laser diode array.

4 is a cross-sectional structural view showing an enlarged part of the AB cross section of the laser diode array shown in FIG.

FIG. 5 is a diagram showing an example of laser characteristics with respect to an input current of a single laser diode.

[Explanation of symbols]

 1 Chip 2 Active Layer 3 Reflector 4 Laser Light 5 Substrate 6 Current Blocking Layer 7 Contact Layer 8 Electrode 9 Common Electrode 10 Element Separation Groove 11 Waveguide

Claims (2)

[Claims] 1. A laser diode array in which a plurality of laser diodes each having an active layer portion formed in a stripe shape are arranged on the same chip, wherein the active layer portion of each laser diode oscillates a laser beam. A laser diode characterized in that it has a waveguide portion which is not performed continuously in the active layer portion, and the waveguide portion and the active layer portion are arranged so as not to be adjacent to each other between adjacent laser diodes. array. 2. The laser diode array according to claim 1, wherein the active layer portion and the waveguide portion continuous with the active layer portion have the same shape and size.