JPH01161792A - Semiconductor laser device and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the interference caused by the reflection on a beam emitting end face without a risk of trouble in laser beam emission, by making the beam reflectance of the beam emitting end face except the optical beam emission point lower than that of said optical beam emission point. CONSTITUTION:The beam reflectance of the beam emitting end face 2 of a semiconductor laser device 1 except the optical beam emission point 5 is lower than that of said optical beam emission point 5. For example, when beam absorptive positive type photoresist film 4a is applied on the surface of the beam emitting end face 2 of the semiconductor laser device 1 and cured, and a beam is emitted from the semiconductor laser device 1 through the optical beam emission point 5 to expose the sensitive resist 4a, the spot just on the optical beam emission point 5 of the sensitive resist 4a is exposed. And then the exposed portion 4b of the sensitive resist 4a is eliminated by etching to bare the optical beam emission point 5. This decreases the beam reflectance of the beam emitting end face 2 except the optical beam emission point 5.

Description

[Detailed description of the invention] The present invention will be described in the following order.

A. Industrial application field 2 B1 Summary of the invention C6 Prior art O9 Problems to be solved by the invention [Fig. 4] E1 Means for solving the problems F0 Effects G. Examples [Figs. Figure 3] H1 Effects of the Invention (A, Industrial Application Field) The present invention relates to a semiconductor laser device and a manufacturing method thereof, and more particularly to a semiconductor laser device used as a light source in an optical head and a manufacturing method thereof.

(B. Summary of the Invention) In order to prevent the laser beam emitted from the semiconductor laser device from being reflected by the recording medium and the light emitting end face and causing interference, the present invention provides light reflection in the light beam emitting area of the light emitting end face. In order to make the light reflectance of other parts of the light output end face different from that of the light beam exit area, a photosensitive resist is applied to the light exit end face of the semiconductor. A self-alert method is used in which a photosensitive resist is exposed to laser light emitted by a laser device.

(C, Prior Art) An optical head using a t-conductor laser device as a light source is used to reproduce optical discs such as compact discs and video discs. Optical heads generally emit laser light emitted from a semiconductor laser device and irradiate it onto the surface of an optical disk, and a photodetector detects the laser light reflected from the surface of the optical disk to read data and prevent tracking errors and focus errors. It performs detection.

A three-beam method is often used to detect tracking errors. In the 3-beam method, one laser beam emitted from a semiconductor laser device is passed through a diffraction grating to obtain three beams, and two of these beams (sub beams) are used to detect tracking errors. It is.

Incidentally, in recent years, magneto-optical disk recording technology, which uses light to magnetically record information on magneto-optical disks, has been developed and is now in the stage of practical application. It will be done. It is common to use an optical head dedicated to optical discs for reproducing optical discs, and to use an optical head dedicated to magneto-optical discs for recording and reproducing data on magneto-optical discs. However, it is predicted that there will be a desire to be able to use one head for both magneto-optical disks and optical disks, and that the optical head for optical disks and the optical head for magneto-optical disks are based on the same principle. Since these are almost the same, the applicant company has attempted to enable recording and reproduction of magneto-optical disks and reproduction of optical disks using one optical head.

(D. Problems to be Solved by the Invention) [Figure 4] However, the optical head that was intended to be usable for both magneto-optical disks and optical disks has problems with tracking error detection when used to play back optical disks. A problem arose in that an offset occurred. A concrete explanation of this point is as follows.

In other words, when reading or recording on a magneto-optical disk using an optical head specifically designed for magneto-optical disks, only about 30% of the laser light emitted from the semiconductor laser device returns to the semiconductor laser device. The interference of the laser light going back and forth between the semiconductor laser device and the semiconductor laser device is negligible. Only about 25% of the light returns to the laser device, so interference is still hardly a problem. However, when an optical disk is played back using an optical head for both magneto-optical disks and optical disks, the surface of the optical disk is made of aluminum, so 90% of the laser light emitted from the semiconductor laser device is reflected by the optical disk and reaches the semiconductor laser device. come back. As a result, the amount of laser light reflected by the semiconductor laser device and the optical disk and traveling back and forth between them increases. This is a 3-beam tracking method (3-spot, DP) that uses a diffraction grating in the optical head.
This is because when P) is adopted, the semiconductor laser device and the disk are not isolated. This interference causes a large C offset in the tracking error detection signal. FIG. 4 is for explaining this phenomenon, and the phenomenon of interference will be explained in more detail with reference to this figure.

In the figure, a denotes a semiconductor laser device, which is mounted on a header b. C is an active layer of the semiconductor laser device a, d is a light emitting end face of the semiconductor laser device a, and a point 2 exposed on the light emitting end face d of the active layer C becomes a light emitting point. e
is a diffraction grating that generates three beams from one laser beam, and f is an optical disk.

When the light emitted from the light emitting point ■ exits the diffraction grating e, it basically creates three optical paths and reaches the three points ■, ■, ■ on the optical disk f, but many other optical paths also occur. . For example, a laser beam that reaches point ■ on optical disk f is reflected there, passes through diffraction grating e, reaches light emitting point ■, is reflected again, passes through diffraction grating e, and reaches point ■, or on the optical disk f. The laser beam that has reached the point ■ is reflected there, passes through the diffraction grating e, reaches a point O above the light emitting point ■ on the light emitting end surface d of the semiconductor laser device a, and is reflected there, passes through the diffraction grating e, and reaches the point O. The optical path leading to ■, and furthermore, the laser beam that reaches point ■ on the optical disk f is reflected there, passes through the diffraction grating e, reaches point ■, is reflected there, passes through the diffraction grating e, and reaches point ■, etc. That's it. As described above, there are many optical paths, and interference occurs at points ■, ■, and ■, and when the optical disk f tilts from the state shown by the solid line to the state shown by the broken line or the state shown by the two-dot chain line, the interference occurs. The light intensity at each point ■, ■, ■ changes.

This gives a DC offset to the tracking servo, which causes tracking to become unstable, and in some cases may even make tracking impossible.

This problem is discussed in the Optical Memory Symposium “86 Proceedings P12.
7-132 December 1986 (co-sponsored by the Japan Society of Applied Physics and the Institute of Electronics, Information and Communication Engineers).

There are several possible solutions to this problem. As one of them, an optical isolator consisting of a polarizing beam splitter or the like is installed between the diffraction grating and the disk, allowing the laser beam from the diffraction grating to pass through, but the laser beam is reflected by the disk and heads toward the diffraction grating. It is conceivable to use an optical isolator to reflect the light and prevent it from causing interference, but this requires an additional optical component called an optical isolator, which is undesirable as it increases the number of components in the optical head and increases the price. . Also, as described in 2127-132 of the above collection of papers, adopting a new differential push-pull method as a tracking servo method may be a solution, but it is not completely established as a technology. There are some unknowns.

In the end, the problem of interference occurs because the laser light is reflected on the semiconductor laser device side, and if the laser light is not reflected on the semiconductor laser device side, or even if it is reflected, the amount of reflected laser light is small, interference will occur. Since this does not occur, it is not necessarily necessary to use an optical isolator or to abandon the established three-spot tracking servo method and adopt a new, unestablished tracking servo method.

Therefore, one possibility is that the disk side surface of the header b is hollowed out as shown by the two-dot chain line in Figure 4, and the light that returns to the point ■ below the light emitting point ■ is reflected downward at the hollowed out part. , so as not to return to the diffraction grating side.

This is certainly effective against the light that returns to the point ■. However, it has no effect on the light that returns to point ■.

By the way, here we talk about the light emitting end face of a general semiconductor laser device. In some cases, the back end face is coated to lower the light reflectance of the laser beam and increase the original laser beam output efficiency. Therefore, it is conceivable to apply the coating to the light-emitting end face, which is the front end face, to lower the light reflectance of the light-emitting end face. but,
If the overall light reflectance of the light emitting end face is lowered, there is a risk that oscillation within the active layer necessary for laser emission will not occur, so it is recommended to reduce the light reflectance by coating the entire light emitting end face. It is also difficult to hire.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a novel semiconductor laser device and a method for manufacturing the same, in which interference due to reflection at a light emitting end face does not occur without causing a risk of interfering with laser emission.

(E. Means for Solving the Problems) In order to solve the above problems, the semiconductor laser device of the present invention has the following steps:
It is characterized in that the light reflectance of other parts of the light emitting end face is lower than that of the light beam emitting area.

In the method for manufacturing a semiconductor laser device of the present invention, in order to make the light reflectance different between the light beam emitting region and other parts of the light emitting end surface, a photosensitive resist is applied to the light emitting end surface, and the laser beam emitted from the semiconductor laser device is coated with a photosensitive resist. It is characterized by self-alignment in which the photosensitive resist is exposed to light.

(F. Effect) According to the semiconductor laser device of the present invention, since the light emitting end face has a low light reflectance except for the light beam emitting region, the amount of reflected light at the light emitting end face can be reduced. , it is easy to reduce the interference to a negligible level. Furthermore, since the light beam emitting region of the light emitting end face does not have a low light reflectance, there is no possibility that laser oscillation will be hindered.

Therefore, it is possible to reduce the amount of reflection at the light emitting end face and prevent interference from occurring without interfering with laser emission.

According to the method for manufacturing a semiconductor laser device of the present invention, the photosensitive resist coated on the light emitting end face is exposed to laser light generated by the semiconductor laser device, so that only the portion of the photosensitive resist on the light beam emitting region is exposed. can be selectively exposed to light. Therefore, it is possible to make the light reflectance of the light beam emitting region different from that of other parts, and it is possible to easily manufacture a semiconductor laser device in which the light reflectance of the other parts is lower than that of the light beam emitting region. Can be done.

(G. Embodiment) [FIGS. 1 to 3] Hereinafter, the semiconductor laser device of the present invention and its manufacturing method will be described in detail according to the illustrated embodiment.

FIGS. 1(A) and 1(B) show one embodiment of the semiconductor laser device of the present invention; FIG. 1(A) is a perspective view, and FIG.
B) is a cross-sectional view.

In the drawings, 1 is a semiconductor laser device, 2 is a light emitting end face, that is, an end face that emits the original laser light used for signal reproduction or writing, and 3 is an active layer.

4 is a light-absorbing film made of, for example, a photosensitive resist. The light absorbing film 4 has an opening 6 formed so as not to cover the portion of the active layer 3 exposed to the light emitting end face 2, that is, the light beam emitting region 5.

According to such a semiconductor laser device, the exposed portion of the active layer 3 of the light emitting end face 2, that is, the portion other than the light beam emitting region 5, is covered with the light absorption film 4, so that the light beam emitting region is covered with the light absorbing film 4. The light reflectance of parts other than 5 becomes significantly low.

Therefore, the amount of light reflected at the light emitting end face 2 can be reduced, and in turn, the DC offset of the tracking servo due to interference can be reduced. Furthermore, since the light beam emission region 5 is not covered with the light absorption film 4, there is no risk of interfering with laser oscillation.

Incidentally, the opening 6 may be coated with an anti-reflection coating.

FIGS. 2A to 2C are cross-sectional views showing one example of a method for manufacturing the semiconductor laser device shown in FIG. 1 in the order of steps.

First, as shown in the figure (A), a positive photoresist film 4a having light absorption properties is coated on the surface of the light emitting end face 2 of the semiconductor laser device 1, and after curing, as shown in the figure (B). In this manner, the semiconductor laser device 1 is caused to emit light, and the photosensitive resist 4a is exposed to the laser light emitted from the light beam emitting region 5 of the semiconductor laser device 1. Then, a portion of the photosensitive resist 4a corresponding to the light beam emission area 5 is exposed to light. 4b is a photosensitive portion of the photosensitive resist 4a. Thereafter, by etching, the photosensitive portion 4b of the photosensitive resist 4a is removed to expose the light beam emitting region 5, as shown in FIG. 4(C). Incidentally, the opening 16 formed by this etching may be coated with an anti-reflection coating.

In this way, by causing the semiconductor laser device 1 to emit light, it is possible to lower the light reflectance of the portion of the light emitting end face other than the light beam emitting area by self-alignment using laser light.

FIGS. 3A to 3E are cross-sectional views showing another example of the method for manufacturing the semiconductor laser device shown in FIG. 1 in the order of steps.

First, as shown in the same figure (A), a negative photoresist film 4C is applied to the light emitting end face 2, and then, as shown in the same figure (B), the semiconductor laser device 1 is caused to emit light to emit a light beam. The photoresist film 4C is exposed to laser light emitted from the region, and then etched to leave only the exposed portion 4d of the photoresist film 4C as shown in FIG. As shown in (E), a light absorbing film 4e is deposited, and then, as shown in (E) of the same figure, the photoresist film exposed portion 4d is removed. Incidentally, after that, an anti-reflection coating may be applied to the opening 6.

A semiconductor laser device as shown in FIG. 1 can also be manufactured by such a method.

Note that a non-reflective photosensitive resist is applied instead of the light absorber, the photosensitive resist is exposed to laser light from a semiconductor laser device, and the light-emitting end face is etched using the photosensitive portion of the photosensitive resist as a mask. By roughening the surface, the light reflectance of the portion of the light emitting end surface other than the light beam emitting area may be reduced, or the photoresist HIQ coated on the light emitting end surface may be used to prevent laser light from a semiconductor laser device. In the present invention, a suitable film is deposited on the light emitting end face, and ions are implanted into the deposited film using the exposed part of the photoresist film as a mask to impart light absorption properties. Various embodiments are possible.

(H, Effect of the Invention) As described above, the semiconductor laser device of the present invention is characterized in that the light reflectance of other parts of the light emitting end face is lower than the light reflectance of the light beam emitting region. It is something.

Therefore, according to the semiconductor laser device of the present invention, reflection at the light emitting end face can be eliminated and the possibility of interference can be eliminated without interfering with laser emission.

Further, in the method for manufacturing a semiconductor laser device of the present invention, in the method for manufacturing a semiconductor laser device in which the light reflectance of other parts of the light emitting end facet is lower than the light reflectance of the light beam emitting region, the light emitting end facet has a photosensitive material. The method is characterized by comprising a step of exposing the photosensitive resist to light output from the semiconductor laser device after applying the resist.

Therefore, by self-alignment, the light reflectance of the light beam emitting region of the light emitting end face can be made different from that of other parts, and the above semiconductor laser device can be manufactured easily.

[Brief explanation of the drawing]

1(A) and 1(B) show one embodiment of the semiconductor laser device of the present invention, in which FIG. 1(A) is a perspective view and FIG. 1(B) is a perspective view.
) is a cross-sectional view, FIGS. 2(A) to (C) are cross-sectional views showing one embodiment of the method for manufacturing the semiconductor laser device of the present invention in the order of steps, and FIGS. 3(A) to (E) are cross-sectional views of the semiconductor laser device of the present invention. FIG. 4 is a sectional view showing another embodiment of the method for manufacturing a laser device in the order of steps, and is an explanatory diagram of interference, which is a problem to be solved by the present invention. Explanation of symbols 1...Semiconductor laser device, 2...Light emission end face, 4a, 4c...Photosensitive resist, 5...Light beam emission region.゛ 1... Hand-held laser device 5. Light and 1-me nail 9B area CA') CB) < C) CA)
CB) CC) CD) CE) @775ff
Cross-sectional diagram showing in@n4rIIJ in process order Figure 3: Interference diagram (problem explanation)

Claims (2)

[Claims] (1) A semiconductor laser device characterized in that the light reflectance of other parts of the light emitting end face is lower than the light reflectance of the light beam emitting region. (2) In a method for manufacturing a semiconductor laser device in which the light reflectance of other parts of the light emitting end face is lower than the light reflectance of the light beam emitting region, the semiconductor laser device is coated with a photosensitive resist on the light emitting end face. A method for manufacturing a semiconductor laser device, comprising the step of exposing the photosensitive resist with a light output of