JPH08162717A - Surface light emitting semiconductor laser - Google Patents

Abstract

PURPOSE: To obtain a semiconductor laser in which high laser output, a uniform large scale cross-sectional intensity distribution of laser light having identical longitudinal and lateral lengths, a single plane laser wave front, and a low divergence angle are satisfied. CONSTITUTION: Surface light emitting semiconductor laser elements I, II are disposed facing the emitting faces each other. A light impinging obliquely on the light emitting part of the surface emitting semiconductor laser element I, II passes each active layer and reflected back on a mirror layer. The reflected light pass the active layer again and leaves the active layer at the same angle as the incident angle before impinging on a next laser element. The laser is constituted to repeat the similar operation thus optically coupling the active layers of respective laser elements in series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting semiconductor laser, and is particularly useful when applied to a laser light source section of a laser processing apparatus and a laser processing apparatus and a laser light source section of a semiconductor laser apparatus for measurement and long distance spatial communication. It is something.

[0002]

2. Description of the Related Art In general, a laser process apparatus is required to have a large output in order to improve a processing capacity, and since light is transmitted to an arbitrary position in space, it is necessary to make a wavefront into a single plane and reduce a divergence angle. In addition, since the optical components used are usually circular or square, it is also necessary to make the laser beam cross-sectional intensity distribution uniform and the vertical and horizontal lengths uniform.

CO is suitable for this purpose.
_{There are 2} lasers and YAG lasers. However, these lasers have drawbacks such as low efficiency of conversion from electric input to light, long oscillation wavelength of infrared rays, poor controllability by computer, and large size of device.

On the other hand, there is a semiconductor laser as a laser that overcomes such drawbacks, but it has not yet reached the advantage of the CO ₂ laser and YAG laser described above.

Table 1 shows a comparison of various kinds of recent semiconductor lasers in which the performances, which are required for the laser process equipment but are said to be defects of the semiconductor lasers, are arranged.

[Table 1]

The following can be understood by referring to the table. That is, an ordinary semiconductor laser alone has a low output and a large divergence angle. A semiconductor laser array is one in which a large number of these are arranged two-dimensionally and the outputs from the semiconductor laser elements at the respective points on the plane are collected and used. This type has an average output of kW
Although the above output is obtained, the laser wavefront is not single and the divergence angle is large. Therefore, it is not directly used as a laser,
It is used to excite a solid-state laser such as YAG to replace a conventional lamp.

In the taper type semiconductor laser amplifier shown in FIG. 8, the width of the active layer 4 is widened to achieve a certain level of performance improvement in order to increase the output and unify the wavefront. Since the thickness is thin, there is a limit to large-scale and large output.

In FIG. 8, 1 is a master oscillator, 2 is an upper electrode, 3 is a cladding layer, 5 is an insulating layer, 6 is a substrate, 7 is a lower electrode, and 8 is laser output light.

The wavefront phase matching type semiconductor laser array shown in FIG. 9 includes a plurality of semiconductor lasers 9a, 9b, 9c, 9
d are arranged in parallel on a plane so that the distance is about the wavelength, and the wavefronts of all the lasers are made to match by the effect that the light waves seep out between the semiconductor lasers 9a to 9d.
Each intensity distribution has a maximum value and is not uniform. In FIG. 9, 10a, 10b, 10c and 10d are active layers, and 11
Laser output lights a, 11b, 11c, and 11d.

The semiconductor laser described above is one in which the optical axis of the laser output light 8, 11a to 11d is made parallel to the surface of the film of the active layers 4, 10a to 10d, but the one made vertical is shown in FIG. It is a surface emitting semiconductor laser. This type of laser alone has a single wavefront and a small divergence angle,
Since the optical path length of the active layer 13 is short (thickness is thin) between the two mirror type cladding layers 12a and 12b, the output is small.
Further, when a large number of surface emitting semiconductor lasers are formed in an array, an output to some extent can be obtained, but a single wavefront is not obtained.

In the figure, 14 is an upper electrode, 15 is an insulating layer, 16 is a substrate, 17 is a lower electrode, and 18 is laser output light.

The above-mentioned drawbacks of the semiconductor laser according to the prior art appear due to the fact that the active layer for emitting light has a thin plate shape. Further, in order to increase the output, the maximum laser intensity per unit area is limited due to the optical damage of the semiconductor material due to the laser light, so that it is necessary to increase the laser light passage cross section, and the surface emitting semiconductor laser is advantageous. However, since only one active layer has a short optical path length for optical amplification, the output is small.

[0013]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, the present invention provides a laser with a large output, a uniform and large laser beam cross-sectional intensity distribution and a uniform vertical and horizontal lengths, and a single laser wave front plane. It is an object of the present invention to find a structure of a semiconductor laser that simultaneously satisfies the reduction of the divergence angle, and to provide a surface emitting semiconductor laser capable of giving the semiconductor laser a laser performance equivalent to that of a YAG laser or a CO ₂ laser.

[0014]

In a YAG laser or a CO ₂ laser, a laser medium corresponding to an active layer of a semiconductor laser is a cylinder or a rectangular parallelepiped, and a laser optical axis is set in the longitudinal direction to form a resonator outside. Therefore, there is no problem as described above. Therefore, it is a specific object to find out a structure in which the active layer of the semiconductor laser can be regarded as a cylinder or a rectangular parallelepiped.

The structure of the first invention for achieving the above object is as follows:
The active layers are optically coupled in series so that the laser optical axis sequentially passes through the active layers of the plurality of surface emitting semiconductor laser device elements.

According to a second aspect of the invention, a plurality of surface emitting semiconductor laser device elements each having a mirror layer disposed on the side opposite to the light emitting surface side of the active layer are arranged with their respective light emitting surfaces facing each other, and each surface emitting semiconductor. The laser beam obliquely incident on the surface of the laser device element passes through each active layer, is reflected by the mirror layer at the back, and then passes through the active layer again. It is characterized in that the laser beam passes through all the surface emitting semiconductor laser device elements by coming out in the direction of and then obliquely entering the next surface emitting semiconductor laser device element.

The structure of the third invention is characterized in that an antireflection coating film is formed on the surface of each light emitting surface.

The structure of the fourth invention is characterized in that a transparent electrode film is formed on the light emitting surface side of the cladding layer of the surface emitting semiconductor laser device element.

A fifth aspect of the invention is characterized in that it has an electrode in which an electric conductor is formed in a stitch shape on the light emitting surface side.

The structure of the sixth invention is characterized in that the aspect ratio of the light emitting surface is set to be larger than 1 such as a rectangle or an ellipse.

A seventh aspect of the invention is characterized in that a power supply for driving a single or a plurality of surface emitting semiconductor laser device elements is provided and each of them is independently controlled in operation.

The structure of the eighth invention is characterized in that the surface emitting semiconductor laser device having a plurality of surface emitting semiconductor laser device elements can be cooled individually or collectively.

[0023]

According to the present invention having the above-described structure, the laser optical axis is successively incident on the large flat surface of each active layer by using a large number of surface emitting semiconductor laser element elements.

In particular, according to the second aspect of the invention, the laser optical axis is obliquely incident on the light emitting surface, is returned by the mirror at the back of the active layer, and is emitted from the surface emitting semiconductor laser device element. It passes through the active layer of the semiconductor laser device element.

The third aspect of the present invention reduces the reflection loss when the laser light is incident on the light emitting surface and realizes the unification of the wavefront.

In the fourth invention, when the area of the light emitting surface is large, a driving current is supplied to the whole to realize a large laser beam cross section.

According to a fifth aspect of the invention, instead of the transparent electrode film having a small light absorption required for the fourth aspect of the invention, a drive current is supplied near the center of the light emitting surface by an opaque thin electric conductor.

A sixth aspect of the present invention reduces the ineffective portion of the semiconductor light emitting surface when the light beam is obliquely incident.

According to a seventh aspect of the present invention, the driving current in each surface emitting semiconductor laser device element is controlled to adjust the laser light amplification factor and the like to realize effective operating conditions.

The eighth invention functions as a cooling means for preventing the semiconductor from being heated because the oscillation efficiency is finite.

[0031]

Embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIG. 1A, the surface emitting semiconductor laser device I comprises a plurality (three in the figure) of surface emitting semiconductor laser device elements (hereinafter referred to as laser device elements) 21 and 2.
2, 23 are arranged side by side in the longitudinal direction.

Each of the laser element elements 21, 22, and 23 is a light emitting portion having a light emitting surface, and in particular, as shown in FIG. 1B, the current supplied from the upper electrode 24 passes through the transparent electrode film 25. The clad layer 26, the active layer 27, the mirror type clad layer 28 which is a mirror layer, and the substrate 29 are configured to flow to the lower electrode 30. The insulating layer 31 is
This is for preventing this current from flowing out of the active layer 27.

Due to the action of this current, electrons and holes are emitted from the cladding layer 26 and the mirror-type cladding layer 28, respectively, into the active layer 27.
Flows into the active layer 27, and the active layer 27 is ready to emit light.
At this time, when the laser beam 32 is incident from the outside, the laser beam 32 enters the inside without being reflected by the antireflection coating film 33 covering the surface of the transparent electrode film 25, and passes through the transparent electrode film 25 and the clad layer 26. Then, the active layer 27 is reached. The light intensity is amplified in the active layer 27 and proceeds to the mirror-type cladding layer 28.
Here, the laser light 32 is returned and returns to the active layer 27 again, and the light intensity is further amplified and exits from the antireflection coating film 33 at the same angle as the incident angle.

That is, the laser element elements 21, 22, 2
3 has a mirror type clad layer 28 which is a mirror layer on the side opposite to the light receiving surface side of the active layer 27, and the laser light 32 obliquely incident on the light emitting surface transmits through the active layer 27 and the mirror type clad layer 28. It is configured to be reflected by, and transmitted through the active layer 27 again, and go out in the opposite direction from the light emitting surface at the same angle as the incident angle. At this time, the shape of the active layer 27 has an aspect ratio larger than 1, but the laser beam cross section is configured to have an aspect ratio of 1 by appropriately adjusting the oblique incident conditions of the laser beam 32.

The substrate 34 serves as a base for manufacturing a semiconductor film, and is also necessary for ensuring the flatness of the mirror layer. The driving power supplies 35, 36 and 37 supply currents to the active layer 27 independently. This drive power supply 35,
Reference numerals 36 and 37 are for controlling the drive current to adjust the laser light amplification factor and the like to realize effective operating conditions.
In some cases, a plurality of laser element elements may be collectively driven by one drive power source.

Further, each laser element element 21, 22, 23
The upper electrode 24, the transparent electrode film 25, the clad layer 26, the active layer 27, and the mirror-type clad layer 28 are electrically insulated from each other.

The embodiment of the present invention is constructed by combining the surface emitting semiconductor laser device I having the above-mentioned configuration.

FIG. 2 shows a first embodiment in which a surface emitting semiconductor laser device I and a surface emitting semiconductor laser device II having four laser device elements 38, 39, 40 and 41 are combined. That is, in the surface-emitting semiconductor laser devices I and II, the light emitting surfaces of the laser device elements 21 to 23 and the laser device elements 38 to 41 are arranged to face each other, and the laser device elements 21 to 21 are arranged.
23 to 38 to 41, the laser light 32 is configured to be obliquely incident and emitted at the same angle as this incident angle, and the center of the light emitting surface of each of the laser element elements 21 to 23 and 38 to 41 is A total reflection mirror 42 and a semitransparent mirror 43 are arranged outside so as to be perpendicular to the incident laser beam 32.

According to the present embodiment, laser oscillation of a single wavefront occurs in the total reflection mirror 42 and the semitransparent mirror and a large number of active layers 27 that emit light, and the laser output light 44 is emitted from the semitransparent mirror 43. It That is, this embodiment functions as an oscillator. The single flatness of the wavefront and the reduction of the divergence angle can be obtained by the total reflection mirror 42 and the semitransparent mirror 43 forming the external resonator.

FIG. 3 shows a second embodiment in which two surface emitting semiconductor laser devices II are combined. In this embodiment, two surface emitting semiconductor laser elements II are arranged so as to face each other, and the laser light 46 from the master oscillator 45 is aligned with the optical axis of the light emitting surface of each of the laser element elements 38 to 41 in accordance with the optical axis for reflection and reflection. It is configured to be incident. Further, each of the laser element elements 38 to 41 is configured to be controlled by independent driving power sources 47, 48, 49 and 50, respectively.

According to this embodiment, the laser light 46 is amplified by each active layer 27 and emitted as the laser output light 51. That is, this embodiment functions as an amplifier.

Further, according to this embodiment, since the laser intensity increases each time it passes through each active layer 27, the laser light amplification factor decreases due to the saturation phenomenon toward the rear. Therefore, in order to efficiently obtain the required laser output light 51, it is necessary to adjust the amplification factor of each active layer 27, and the current supplied from each drive power source 47 to 50 is controlled so as to be appropriately distributed. .

When the laser light 32 that is reflected and bent a plurality of times in the above-described two embodiments is virtually extended linearly, it becomes as shown in FIG. 4, which is the basic principle of the present invention.

Therefore, according to the above-mentioned embodiment, the shape of the active layer 27 has an aspect ratio larger than 1, but the laser beam cross section has an aspect ratio of 1 by appropriately adjusting the oblique incidence condition. In particular, the same operation as that of a YAG laser or a CO ₂ laser, in which a light beam passes in a longitudinal direction in a cylindrical or rectangular parallelepiped laser medium, can be expected, and the light quality becomes good.

In order to increase the output, the area of the surface emitting semiconductor laser devices I and II is increased and the intensity per unit area of the laser beam 32 is reduced by oblique incidence to avoid optical damage.
By increasing the number of the surface emitting semiconductor laser devices I and II, the effective optical path length can be increased and the output can be increased.

When the area is increased, the conventional surface emitting semiconductor laser cannot supply the activation current to the center of the light emitting surface, but the transparent electrode film 25 supplies the activation current. Uniform size enlargement of the laser beam cross-sectional intensity distribution and equalization of the vertical and horizontal lengths can be achieved by such element arrangement.

Next, the flattening of the laser wavefront and the reduction of the divergence angle are achieved by using the external resonator because the surface emitting semiconductor laser devices I and II are optically engaged in series in this arrangement. it can. At this time, if there is reflected light from each light emitting surface, a large number of wavefronts will exist in the resonator, so the antireflection coating film 33 is necessary. The antireflection coating film 33 also helps reduce output loss.

In general, since the output and the emission wavelength of the semiconductor laser change depending on the value of the driving current, the surface emitting semiconductor laser devices I and II are used to adjust the wavelength mismatch and the output saturation.
It is effective that the drive currents of the drive power sources 35 to 37 and 47 to 50 can be independently controlled. Incidentally, the YAG laser and the CO ₂ laser do not have the function of changing the current distribution inside the laser medium to adjust the laser gain and the like.

In order to supply a current to the vicinity of the center of the large-diameter light emitting surface, an electric conductor is attached to the light emitting surface in the form of a thin mesh instead of the transparent electrode film 25 to form an electrode, and a current is supplied. You may use.

A third embodiment of the present invention having this electrode is shown in FIG. The structure of this embodiment is the same as that of FIG. 1 except for the electrodes. Therefore, the same parts are designated by the same reference numerals, and the duplicated description will be omitted.

As shown in FIG. 5, a part of the upper electrode 52 is formed in a stitch pattern on the light emitting surface. Further, in this embodiment, the two light emitting portions are not electrically insulated.

FIGS. 6 and 7 are block diagrams showing fourth and fifth embodiments in which a cooling function is added to the second embodiment.

As shown in FIG. 6, in the fourth embodiment, the surface-emitting semiconductor laser devices II and II are arranged so as to face each other, and the entire surface emitting semiconductor laser devices II and II are placed in a container 5.
The container 53 is filled with a cooling gas or liquid. These refrigerants may be allowed to flow if necessary. Further, windows 54 and 55 are provided in the portion which becomes the entrance and exit of the laser light 32.

As shown in FIG. 7, in the fifth embodiment, the lower electrodes 30 of the surface-emitting semiconductor laser devices II, II facing each other are set to the ground potential and brought into contact with the heat transfer plates 56, 57.
Refrigerant is caused to flow inside the heat transfer plates 56 and 57 to remove heat.

According to the above fourth and fifth embodiments, since the oscillation efficiency is finite, it functions as a means for preventing the semiconductor from being heated.

[0057]

According to the present invention as specifically described in connection with the above embodiments, the laser optical axis can be set in the direction crossing the plane of the large planar active layers of a large number of semiconductor lasers, and the active layers are connected in series. Since they can be combined, they can simultaneously satisfy the laser performances of high output, uniform and large laser beam cross-sectional intensity distribution, uniform vertical and horizontal lengths, single flatness of laser wavefront, and reduced divergence angle. It has high output and high quality laser performance comparable to lasers and CO ₂ lasers.

On the other hand, the semiconductor laser has advantages such as a compact device, easy output change, variable wavelength, visible light oscillation, and good computer controllability as compared with the YAG and CO ₂ lasers. It is expected that not only process applications but also new applications will be opened due to the synergistic effect of.

[Brief description of drawings]

FIG. 1 is a structural diagram showing a surface emitting semiconductor laser device used in an embodiment of the present invention.

FIG. 2 is a structural diagram showing a first embodiment of the present invention.

FIG. 3 is a structural diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining the operation principle of the present invention.

FIG. 5 is a structural diagram showing a third embodiment of the present invention.

FIG. 6 is a structural diagram showing a fourth embodiment of the present invention.

FIG. 7 is a structural diagram showing a fifth embodiment of the present invention.

FIG. 8 is a structural diagram showing a tapered semiconductor laser amplifier according to a conventional technique.

FIG. 9 is a structural diagram showing a wavefront phase matching type semiconductor laser array according to a conventional technique.

FIG. 10 is a structural diagram showing a surface emitting semiconductor array according to a conventional technique.

[Explanation of symbols]

I, II surface emitting semiconductor laser device 21, 22, 23, 38, 39, 40, 41 surface emitting semiconductor laser device element 25 transparent electrode 27 active layer 28 mirror type cladding layer 32 laser light 33 non-reflective coating film 35, 36, 37, 47, 48, 49, 50 Drive power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuichi Matsuda 2-1-1 Niihama, Arai-cho, Takasago-shi, Hyogo Mitsubishi Heavy Industries Ltd. Takasago Research Institute

Claims (8)

[Claims] 1. A surface emitting semiconductor laser in which active layers are optically coupled in series so that a laser optical axis sequentially passes through each active layer of a plurality of surface emitting semiconductor laser device elements. 2. A plurality of surface-emitting semiconductor laser device elements, each having a mirror layer disposed on the side opposite to the light-emitting surface side of the active layer, are arranged such that their respective light-emitting surfaces face each other, and are oblique to each surface-emitting semiconductor laser device element surface. The laser beam incident on is transmitted through each active layer, reflected by the mirror layer at the back and transmitted through the active layer again, and exits from the surface emitting semiconductor laser device element at the same angle as the incident angle in the opposite direction, The surface emitting device according to claim 1, wherein the laser beam passes through all the surface emitting semiconductor laser device elements by being obliquely incident on the next surface emitting semiconductor laser device element. Semiconductor laser. 3. The surface emitting semiconductor laser according to claim 2, wherein a non-reflection coating film is formed on the surface of each light emitting surface. 4. A surface emitting semiconductor laser according to claim 2, wherein a transparent electrode film is formed on the light emitting surface side of the cladding layer of the surface emitting semiconductor laser device element. 5. The surface emitting semiconductor laser according to claim 2 or 3, further comprising an electrode in which an electric conductor is formed in a stitch pattern on the light emitting surface side. 6. The surface emitting semiconductor laser according to claim 2, wherein the aspect ratio of the light emitting surface is larger than 1 such as a rectangle or an ellipse. 7. A surface emitting semiconductor laser device element is provided with a power source for driving a single element or a plurality of elements collectively, and each of them is independently controlled for operation [claim 2].
A surface emitting semiconductor laser according to claim 6. 8. A surface emitting semiconductor laser device having a plurality of surface emitting semiconductor laser device elements is configured to be cooled individually or collectively in a plurality [claim 2].
A surface emitting semiconductor laser according to claim 7.