JP2002335046A - Semiconductor laser array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser array capable of obtaining a laser beam having a desired light intensity distribution. SOLUTION: The LD bar is a semiconductor laser array of a plurality of semiconductor laser elements LD arranged in a one-dimensional shape. The density of those laser elements LD capable of light emission is higher at both ends than at a center portion. In the intensity distribution of a laser beam pattern emitted from the laser array in the arraying direction of the laser elements LD, the intensity is higher at both ends than at the central portion. The intensity at both ends of the pattern is relatively increased to suppress the relative overheat of the center portion when a work is irradiated with the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor laser array.

[0002]

2. Description of the Related Art A semiconductor laser array (LD bar) in which a plurality of semiconductor laser elements (laser diodes: LD) are one-dimensionally arranged on the same substrate, and the LD bars are individually
LD laminated structure (LD stack) formed by laminating a plurality of layers in a direction perpendicular to both the arrangement direction of D and the emission direction of laser light
It has been known. Use of high-power laser light of several tens of watts to several kW emitted from these semiconductor laser devices is being studied for laser processing such as heat treatment.

FIG. 12 is a front view of a normal LD bar.
This LD bar has a plurality of LDs arranged one-dimensionally at equal intervals. The output intensity distribution of each LD constituting the LD bar itself is a Gaussian distribution.

FIG. 13 is a graph showing an intensity distribution of a band-like laser beam emitted from the LD bar in the arrangement direction.
Since a plurality of LDs are evenly arranged at a desired pitch,
The low-intensity region in the intensity distribution of each LD is superimposed on the low-intensity region in the intensity distribution of an adjacent LD, and as shown in the graph, the laser light intensity within a predetermined section along the LD array direction. Is substantially constant.

When an LD bar or LD stack is used as a light source for processing such as heat treatment, it is required that the temperature distribution in a laser beam irradiation area on a workpiece be uniform.
If the laser light has a constant intensity distribution along the arrangement direction as described above, it seems that the temperature distribution along the arrangement direction of the laser light irradiation region on the workpiece is also uniform.

However, the temperature distribution on the workpiece irradiated with the laser beam having the above-mentioned light intensity distribution has a high temperature near the center of the laser beam irradiation region, and the peripheral portion (end portion) of the laser beam irradiation region. ) Is lower than the center. This is because the peripheral portion of the laser light irradiation area is adjacent to the laser light non-irradiation area (low temperature area), so that heat dissipation due to heat conduction is large.

In order to solve this problem, the output intensity pattern of the linear light beam from the LD bar is defined as a light beam having an M-shaped intensity distribution in which the peripheral portion (end portion) is higher in intensity than the central portion. What is necessary is just to irradiate a workpiece.

In order to obtain an irradiation laser beam having an M-shaped light intensity distribution, it is conceivable to form a beam having a rectangular output intensity distribution from an ordinary LD bar into an M-shaped beam using an optical system. .

In an ordinary LD bar, it is conceivable to obtain light of a desired light intensity pattern by independently driving the individual LDs and emitting light of different intensities from them. Japanese Patent Application Laid-Open No. 2-122584 discloses a method of outputting light having different intensities from individual LDs of an LD bar.

FIG. 14 is a sectional view of an LD bar described in the publication. In the LD bar described in this publication, the stripe width of each LD is changed and each LD is independently driven in order to obtain different outputs from each LD.

[0011]

However, usually,
Since the LD bar used for processing needs to flow a large current in order to obtain a high output, the electrodes are shared so that the current is not concentrated on one of the LDs. Japanese Patent Application Laid-Open No. 2-122584 discloses an L in which LDs having different stripe widths are arranged.
In the case of using a common electrode in the D array and supplying a large current sufficient to obtain a high output for laser processing, the current is concentrated on the stripe (LD) having a low resistance, and the LD is destroyed. Therefore, in the conventional semiconductor laser array, light having a desired intensity and intensity distribution cannot be obtained.

The present invention has been made in view of such a problem, and has as its object to provide a semiconductor laser array capable of obtaining a laser beam having a desired light intensity distribution.

[0013]

In order to solve the above-mentioned problems, a semiconductor laser array according to the present invention is a semiconductor laser array comprising a plurality of semiconductor laser elements arranged one-dimensionally. It is characterized in that the density of those capable of emitting light is higher at both ends than at the center.

In this case, the intensity distribution of the laser beam pattern emitted from the semiconductor laser array along the semiconductor laser element arrangement direction is higher at both ends than at the center.
That is, by making the intensity of both ends of the pattern relatively higher than that of the central part, it is possible to suppress the relative overheating of the central part when laser light is irradiated on the workpiece.

As a preferred example which can achieve such a configuration, the central portion of the plurality of semiconductor laser elements is made not to emit light. In this case, after a plurality of semiconductor laser elements are formed at the same time, a structure may be employed in which a drive current is not applied only to the semiconductor laser element at the center.

Another preferred example of achieving the above configuration is that a plurality of semiconductor laser elements are formed only at both ends excluding the center. In this case, non-light emission at the center can be reliably achieved.

As another preferred example that can achieve the above-described configuration, the central part of the plurality of semiconductor laser elements is made non-light emitting, and the semiconductor laser elements at both ends at each of both ends are made capable of emitting light. A part of the semiconductor laser element closer to the center of the semiconductor laser element does not emit light. In this case, the central portion does not emit light, but a portion also does not emit light at both ends, so that in the boundary region between the center portion and both ends of the semiconductor laser array, the intensity of the laser light pattern can be reduced stepwise, The temperature distribution in the laser beam irradiation area can be made more uniform.

Another preferred example of achieving the above-mentioned configuration is that the density itself of the semiconductor laser device is higher at both ends than at the center. In this case, when each semiconductor laser element emits light, the intensity at both ends of the pattern becomes relatively higher than that at the center.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor laser array according to an embodiment will be described. The same reference numerals are used for the same elements, and duplicate descriptions are omitted.

FIG. 1 is a front view of a semiconductor laser array (LD bar) according to the first embodiment. FIG. 9 is an enlarged view of both ends of the LD bar shown in FIG.

In the LD bar, in a semiconductor laser array in which a plurality of semiconductor laser elements LD are arranged one-dimensionally, the density of light-emitting ones of the semiconductor laser elements LD is larger at both ends than at the center. Is high. The intensity distribution of the laser light pattern emitted from the semiconductor laser array along the arrangement direction of the semiconductor laser elements LD is higher at both ends than at the center. That is, by making the intensity of both ends of the pattern relatively higher than that of the central part, it is possible to suppress the relative overheating of the central part when laser light is irradiated on the workpiece.

In this embodiment, the central portion of the plurality of semiconductor laser elements LD is not emitting light. After a plurality of semiconductor laser elements LD are formed at the same time, a drive current is not applied only to the central semiconductor laser element LD. That is, a difference from the conventional LD bar is that a drive current is supplied to some of the individual semiconductor laser elements LD constituting the LD bar in order to obtain an output beam having a desired light intensity distribution. That is, the configuration is such that it is not performed.

The number of the semiconductor laser elements LD of this embodiment is 16 per LD bar. The LD bars are provided in the LD-forming regions, which are arranged at equal intervals, on the common semiconductor substrate 1 made of n-type GaAs, respectively, with the n-type AlGaAs cladding layer 2, the AlGaAs active layer 3, the p-type AlGaAs cladding layer 4, and the p-type AlGaAs cladding layer 4. Each of the semiconductor laser elements LD is separated by sequentially laminating a GaAs type contact layer C and forming a trench between the semiconductor laser elements LD.

The entire exposed surface including the surface of the p-type GaAs contact layer C located on the uppermost surface is made of SiO ₂ or SiN.
Alternatively, it is covered with an insulating film 5 in which these are combined. After stacking the semiconductor layers 2, 3, 4, C and the insulating film 5, the insulating film 5 is formed by a photolithography process using a mask pattern in which a p-side electrode formation region of each semiconductor laser device LD is opened.
After the p-side electrode formation region is opened, a p-side electrode (common electrode) 6 made of Ti / Pt / Au or the like is formed in the opening by a plating method, an electron beam evaporation method, or the like. To p-type GaAs contact layer C and p-type Al
It is electrically connected to the GaAs cladding layer 4.

A back surface n-type electrode 7 made of AuGe / Ni / Au or the like is formed on the entire surface of the common semiconductor substrate 1 opposite to the LD mounting surface.

Here, since an opening for forming an electrode is not formed on the p-type GaAs contact layer C located at the center, even if a voltage for supplying a driving current is applied to the electrode 6, the driving current is not increased. It is not supplied, and the semiconductor laser element LD at the center does not emit light. Usually, at the time of photolithography, the insulating film is opened by a mask pattern having an opening in a region corresponding to each semiconductor laser element LD,
In the present embodiment, on the insulating film corresponding to the semiconductor laser elements LD other than the five semiconductor laser elements LD at both ends, that is, the insulating films corresponding to the six semiconductor laser elements LD at the center,
A mask pattern in which no opening is formed is applied, and the insulating film 5 is left on the entire upper surface of the six semiconductor laser elements LD located at the center. Thus, even if the p-side electrode 6 is formed on each semiconductor laser element LD as described above, the electrodes 6 on the six central semiconductor laser elements LD are not electrically connected to the contact layer C. No current will be supplied.

This structure has an advantage that it can be manufactured by the same manufacturing method as the conventional one by changing only the mask pattern.

FIG. 2 is a graph showing the light intensity of the laser beam pattern emitted from the LD bar along the arrangement direction of the semiconductor laser elements LD. According to the graph, a concave output intensity distribution in which the intensity of the laser output was increased only at both ends was obtained.

FIG. 3 is a front view of the LD bar according to the second embodiment. In the first embodiment, the individual semiconductor laser elements L arranged at equal intervals on the n-type GaAs substrate 1
During D, the drive current is not supplied to the predetermined semiconductor laser element LD. However, in the LD bar of the second embodiment, the arrangement of the LD is changed according to a desired light output intensity pattern. That is, in the LD bar of the present embodiment,
The difference from the first embodiment is that a plurality of semiconductor laser elements LD are formed only at both ends excluding the center.
In this case, non-light emission at the center can be reliably achieved.

More specifically, only the five semiconductor laser elements LD located at both ends of the first embodiment are n-type G laser diodes.
It was formed on an aAs substrate 1. Thereby, the light output intensity distribution of FIG. 2 can be realized as in the first embodiment.

FIG. 4 is a front view of an LD bar according to the third embodiment. In the first embodiment, by covering the entire surface of these contact layers C with the insulating film 5 for the six semiconductor laser elements LD at the center, only the output at both ends of the linear light beam is obtained. , A concave output intensity pattern was obtained. In the present embodiment, an LD bar having a desired output intensity distribution is formed by appropriately selecting a non-emitting semiconductor laser element LD.

That is, the central part of the plurality of semiconductor laser elements LD is made non-luminous, and the semiconductor laser elements LD at both ends at each of both ends are allowed to emit light. Some of them are non-light emitting. In this case, the central part does not emit light,
Since both ends are partially non-emissive, the intensity of the laser light pattern can be reduced stepwise in the boundary area between the center and both ends of the semiconductor laser array, and the temperature distribution in the laser light irradiation area can be made more uniform. can do.

FIG. 5 is a graph showing the light intensity of the laser beam pattern emitted from the LD bar along the arrangement direction of the semiconductor laser elements LD. An output intensity distribution was obtained in which the intensity of the laser output gradually increased from the center toward both ends.

FIG. 6 is a front view of an LD bar according to the fourth embodiment. In this semiconductor laser array, the density of the semiconductor laser elements LD at both ends is higher than the density of the semiconductor laser elements LD at the center. More specifically, the distance between the semiconductor laser elements LD adjacent at both ends is equal to the distance between the semiconductor laser elements L adjacent at the center.
D is smaller than the interval between D, and the interval becomes narrower as the distance from the center increases. When each semiconductor laser element LD emits light, the intensity at both ends of the pattern becomes relatively higher than that at the center, and the M-shaped output intensity pattern shown in FIG. 5 can be realized.

Each of the semiconductor laser elements LD in the above-described LD bar has a current confinement structure realized by the insulating film 5. However, the structure of the semiconductor laser element LD itself is not particularly limited. Can be used.

FIG. 7 is a front view of an LD bar in which the semiconductor laser element LD itself has a different structure from the above-described LD bar. FIG. 10 is an enlarged view of both ends of the LD bar shown in FIG. This semiconductor laser device LD differs from that of the first embodiment only in that an n-type GaAs current blocking layer CB is added to those shown in FIGS. That is, the p-type AlGaAs cladding layer 4 is formed by selective burying growth.
An n-type GaAs current blocking layer CB is formed around the
A p-type GaAs contact layer C is formed inside the type GaAs current blocking layer CB, and a current confinement structure of the semiconductor laser device LD is realized. Other configurations are shown in FIGS.
Are the same as those shown in FIG.

FIG. 8 is a front view of an LD bar in which the semiconductor laser device LD itself has a further different structure from the above-described LD bar. FIG. 11 is an enlarged view of both ends of the LD bar shown in FIG. This semiconductor laser device LD differs from that of the first embodiment only in that an n-type GaAs current blocking layer CB ′ is added to those shown in FIGS. That is,
After the p-type GaAs contact layer C is formed on the p-type AlGaAs cladding layer 4, protons are implanted around the p-type AlGaAs cladding layer 4 by ion implantation to make the implanted portion a high-resistance layer, and the current of the semiconductor laser element LD is increased. A constriction structure has been realized. Other configurations are the same as those shown in FIGS.

It should be noted that, in the above description, an L-type AlGaAs material is used.
The example in which the D bar is formed has been described, but the material is not limited to this. For example, an InGaAsP-based or AlGaI
Each semiconductor laser element can also be composed of an nP-based (In) GaN-based compound semiconductor.

Since the above-mentioned electrodes 7 and 6 are common electrodes, a conductor (metal) can be used as an electrode, and a large current can be supplied with a sufficiently low resistance. . However, in order to realize the above intensity distribution, it is conceivable to divide the individual electrodes 6 of the semiconductor laser element LD and to use each of the electrodes 6 as an independent drive system.
In this case, patterning is performed so that the electrode 6 is divided for each semiconductor laser element LD, and the thickness thereof is set to 10 μm.
m. In such a case, an electron beam evaporation method is used as a method for forming the electrode 6.

[0040]

As described above, according to the semiconductor laser array of the present invention, laser light having a desired light intensity distribution can be obtained.

[Brief description of the drawings]

FIG. 1 shows a semiconductor laser array (LD) according to a first embodiment.
FIG.

FIG. 2 is a graph showing a light intensity distribution of a laser beam pattern emitted from an LD bar.

FIG. 3 is a front view of an LD bar according to a second embodiment.

FIG. 4 is a front view of an LD bar according to a third embodiment.

FIG. 5 is a graph showing a light intensity distribution of a laser beam pattern emitted from an LD bar.

FIG. 6 is a front view of an LD bar according to a fourth embodiment.

FIG. 7 is a front view of an LD bar in which the semiconductor laser element LD itself has another structure.

FIG. 8 is a front view of an LD bar in which the semiconductor laser element LD itself has another structure.

FIG. 9 is an enlarged view of both ends of the LD bar shown in FIG.

FIG. 10 is an enlarged view of both ends of the LD bar shown in FIG.

FIG. 11 is an enlarged view of both ends of the LD bar shown in FIG.

FIG. 12 is a front view of a normal LD bar.

FIG. 13 is a graph showing an intensity distribution of a band-like laser beam emitted from an LD bar in an arrangement direction.

FIG. 14 is a cross-sectional view of an LD bar described in the publication.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Common semiconductor substrate, 2 ... Cladding layer, 3 ... Active layer, 4
... clad layer, 5 ... insulating film, 6 ... electrode, 7 ... electrode, C ...
Contact layer, CB: current blocking layer, LD: semiconductor laser element.

Continuing from the front page (72) Inventor Takayuki Uchiyama 1126-1, Nomachi, Ichinomachi, Hamamatsu City, Shizuoka Prefecture Inside (72) Inventor Satoshi Oishi 1126-1, Nomachi, Ichinomachi, Hamamatsu City, Shizuoka Prefecture In Hamamatsu Photonics Corporation F term (reference) 4E068 CD01 CD05 5F073 AA08 AA09 AB05 BA09 CA02 CA07 CA13 CA14 CB02 EA24 EA27 EA28 EA29 GA31 GA37

Claims (5)

[Claims] 1. In a semiconductor laser array in which a plurality of semiconductor laser elements are arranged in a one-dimensional manner, the density of the semiconductor laser elements capable of emitting light is higher at both ends than at a center. Characteristic semiconductor laser array. 2. The semiconductor laser array according to claim 1, wherein said central portion of said plurality of semiconductor laser elements does not emit light. 3. The semiconductor laser array according to claim 1, wherein said plurality of semiconductor laser elements are formed only at said both ends except for said central part. 4. The semiconductor laser device at both ends of each of the both end portions is capable of emitting light, and a part of the semiconductor laser devices at the both end portions near the central portion is not emitting light. 3. The semiconductor laser array according to 2. 5. The semiconductor laser array according to claim 1, wherein the density of the semiconductor laser elements is higher at both ends than at the center.