JP2000196173A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser device which is capable of stably reading out a disk without inducing a tracking error by a method wherein a laser chip is so arranged at a position so as not to make return light impinge on its light projecting edge face. SOLUTION: First, a laser chip 10 is mounted in a recess 11a of depth D of a sub-mount 11, and a laser beam rise mirror 12 is provided in front of the laser chip 10. A laser beam P emitted from the laser chip 10 is reflected upward at an angle of 90 deg. by the mirror 12 and made to impinge on a disk read optical system. A reflected light P1 from a disk is reflected from the reflecting surface 12a of the mirror 12 to pass over the laser chip 10, so that it is restrained from returning to the optical system reflecting again from a front-side light projection edge face 10b. Another reflected light P2 reflected from the disk is scattered by the electrode face 10c of the laser chip 10, so that it never returns to the optical system reflecting again. Therefore, a semiconductor laser device of this constitution is capable of stably reading out a disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used as a light source of an optical head used in a device for a compact disk (CD) and the like.
In particular, the present invention relates to a semiconductor laser device having no tracking error due to return light reflection.

[0002]

2. Description of the Related Art When a semiconductor laser chip is used as a light source in a three-beam optical recording device, an optical reproducing device, or the like, a laser beam is generally divided into one main beam and two sub beams. To project onto the disc.

As shown in FIG. 8, these two sub-beams are reflected from the disk, and are referred to as P1 and P2.
From the active layer 1a at a position of about 75 μm.

Therefore, the thickness t1 of the growth layer of the laser chip 1 is about 10 μm, and the thickness t2 of the substrate is about 90 μm.
In this case, P1 is not reflected on the front-side light-emitting end face 1b of the laser chip 1, but P2 is reflected again on the front-side light-emitting end face 1b of the laser chip 1, and this is read as P2 '. Causes noise and tracking errors.

FIG. 9 shows a case where the polarity is opposite to that of the laser chip shown in FIG.

The thickness t1 of the growth layer of the laser chip 2 is about 1
When the thickness t2 of the substrate is about 90 μm,
Although P2 is irregularly reflected (scattered) by the rough surface portion 8 of the submount or stem and does not re-reflect, P1 is reflected again as P1 'on the front-side light emitting end face 2b of the laser chip 2.

Therefore, conventionally, as shown in FIG. 10, the growth surface t1 of the laser chip 3 is increased to about 50 μm by liquid or vapor phase growth, and the thickness t2 of the substrate is set to about 50 μm. Accordingly, a method of preventing both P1 and P2 from being reflected by the front-side light emitting end face 3b of the laser chip 3 is implemented.

As shown in FIG. 11, a rough surface portion 4c is formed by dicing on the light emitting end surface 4b on the front surface side of the laser chip 4, and the reflected light P1 from the disk is irregularly reflected by the rough surface portion 4c. There is a method for preventing reflected light from returning to the optical system again (Japanese Patent Application Laid-Open No. 61-128587). The reflected light P2 is irregularly reflected (scattered) by the rough surface portion 8 of the stem and does not re-reflect.

As shown in FIG. 12, an inclined surface is formed by etching or the like on the light emitting end surface 5b (part of the substrate) of the front surface side of the laser chip 5, and the reflected light P from the disk is formed.
There is a method (JP-A-1-166584) for preventing the reflected light from returning to the optical system again by reflecting P2 'in the inclined portion 5c as P2' in the oblique direction.

As shown in FIG. 13, a black material (a low light reflection material) is applied to a portion of the front surface light emitting end face 6b of the laser chip 6 where the reflected light P2 from the disk is irradiated.
6c, there is a simple method of absorbing the reflected light P2 from the disk by the 6c and reducing the light intensity of the re-reflected light P2 'to about half or less (Japanese Patent Application Laid-Open No. Sho 62-18080).

Further, as shown in FIG. 14, an end face protective film 7 formed on a front light emitting end face 7b of the laser chip 7 is formed.
c, the thickness of the part B (about the lower half of the end face) including the active layer 7a is so-called λ / 2, and the thickness of the part (about the upper half of the end face) irradiated with the reflected light P1 from the disk is λ / 2.
There is a method of reducing the light intensity of the re-reflected light P1 'at A by using a low reflection film of / 4 (Japanese Patent Application Laid-Open No. 62-104093). Note that P2 is irregularly reflected (scattered) by the rough surface portion 8 of the stem and does not re-reflect.

[0012]

However, in the method of FIGS. 10 and 14 described above, the step of forming an element (chip) becomes complicated, and in the method of FIGS. 11 and 12, the wafer is cracked or chipped. Are likely to occur, and handling in the manufacturing process is very difficult.

In the method shown in FIG. 13, there is a possibility that the end face (especially near the active layer) is contaminated by the black material.

An object of the present invention is to solve such a problem.

[0015]

According to a first aspect of the present invention, there is provided a semiconductor laser device comprising: a heat sink or a submount; at least a laser chip; and a mirror disposed in front of a light emitting end face of the laser chip. In the semiconductor laser device provided with the above, the above object is achieved by that the laser chip does not allow the return light to enter the light emitting end face.

In the semiconductor laser device according to the present invention (claim 2), the above object is achieved by providing the heat sink or the submount having a concave portion and mounting the laser chip in the concave portion.

[0017] In the semiconductor laser device according to the present invention (claim 3), the mirror according to claim 1 or 2, wherein the mirror emits light to the laser chip light emitting end face at a return light incident position on the laser chip side end face. The above object is achieved by providing the re-entry prevention region.

[0018] In the semiconductor laser device according to the present invention (claim 4), according to claim 3, the light re-entry prevention region is
The above object is achieved by forming the mirror by removing the mirror.

In the semiconductor laser device according to the present invention (claim 5), in claim 3, the light re-entry prevention region is
The above object is achieved by forming a low reflection film.

[0020] In the semiconductor laser device according to the present invention (claim 6), in claim 3, the light re-entry blocking region is
The above object is achieved by having a rough surface.

[0021] In the semiconductor laser device according to the present invention (claim 7), according to claim 1 or 2, the return light incident surface of the mirror is positioned with respect to the laser chip light emitting end surface.
The above object is achieved by the direction in which no return light is incident.

Hereinafter, the operation of the present invention will be described.

By arranging the laser chip and the mirror at appropriate positions, it is possible to prevent the sub-beam reflected from the disk from being reflected at the light emitting end face of the laser chip or other places and returning to the optical system again. It is possible to read the disk stably without causing an error.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention. First, the laser chip 10 is
The laser chip 1 is mounted in the concave portion 11a having a depth D of
In front of the front side of the mirror 0, a mirror 1 for starting a laser beam
2 are provided. The laser beam P from the laser chip 10 is reflected by the reflecting surface 12a of the mirror 12 into 90 ° information, and enters the optical system for reading a disk.

The reflected light P1 from the disk is reflected by the reflecting surface 12a of the mirror 12, but passes above the laser chip 10 as shown in the figure, is reflected again by the front light emitting end face 10b, and returns to the optical system. Never.

The reflected light P from the other disk
2 also scatters on the electrode surface 10c of the laser chip 10 and does not reflect again to return to the optical system.

In this case, the reflected light P1, P
2 is about 7 from the active layer 10a of the laser chip 10, respectively.
Since the light is incident on a position separated by 5 μm, the distance L1 between the front light emitting end face 10b of the laser chip 10 and the position where the laser beam P of the laser chip 10 is reflected by the mirror 12 is 75.
It must be less than μm.

In FIG. 1-2, the laser chip 10 and the mirror 1 are shown.
2 will be described in detail.

The distance L2 until the laser beam P emitted from the active layer 10a of the laser chip 10 intersects the submount surface 11b is L2, and the distance between the front light-emitting end face 10b of the laser chip 10 and the tip of the mirror 12 is L3. If the distance from the position where the laser beam P of the laser chip 10 is reflected by the mirror 12 is L1, and the height difference between the submount surface 11b and the active layer 10a of the laser chip 10 is h1,
These must satisfy the following relationship.

[0031]

(Equation 1)

As an example, if the substrate thickness (height of the active layer 10a) h2 of the laser chip 10 is 90 μm and the depth D of the concave portion 11a of the submount 11 is 80 μm, h1 is 10 μm.

At this time, when the spread angle α of the laser beam P is 40 °, the laser beam P is
Is about 27 μm before the intersection with. That is, at this time, the front light-emitting end face 1 of the laser chip 10
The distance L3 between Ob and the selection of the mirror 12 must be less than 27 μm.

In this case, the distance L1 between the front light emitting end face 10b of the laser chip 10 and the position where the laser beam P of the laser chip 10 is reflected by the mirror 12 is 37 μm (75 μm).
μm), the condition for irradiating and scattering the reflected light P2 from the disk on the electrode surface 10c of the laser chip 10 is sufficiently satisfied.

When L2 <L3, a part or most of the laser beam P is not reflected by the mirror 12.

The depth D of the concave portion 11a of the submount 11 must be designed so that the height difference h1 between the submount surface 11b and the active layer 10a of the laser chip 10 is 0 μm <h1 <75 μm.

As described above, when the substrate thickness h2 of the laser chip 10 (the height of the active layer 10a) is 90 μm, the depth D of the concave portion 11a on the laser chip mounting surface is 0 μm ≦ D ≦
When the height is 15 μm, the height difference h1 between the submount surface 11b and the laser chip 10 is 75 μm ≦ D ≦ 15 μm, and when the height difference h1 between the submount surface 11b and the active layer 10a of the laser chip 10 is 75 μm ≦ h1 ≦ 90 μm. And the conditions of h1 <75 μm and 75 μm> L1 cannot be satisfied. That is, as shown in FIG. 1-3 (when h1 = 0 μm), after the reflected light P2 from the disk is reflected by the mirror 12, the reflected light P2 is further reflected by the front-side light-emitting end face 10b of the laser chip 10, and the optical system again. Again, which may lead to a disk tracking error.

FIG. 2 shows a second embodiment according to the present invention.

This embodiment is different from the first embodiment in that the reflected light from the disk is not reflected by the light emitting end face of the laser chip even when the laser chip mounting surface of the submount 13 has no concave portion. Things.

By cutting off the tip of the mirror 14 for raising the laser beam to have a shape as shown in FIG. 2A, the mirror 14 can be arranged at a position closer to the front of the laser chip 10. Things.

Accordingly, even when the substrate thickness h2 of the laser chip 10 (height of the active layer 10a) is 75 μm or more, the front light-emitting end face 10b of the laser chip 10 and the position where the laser beam P is reflected by the mirror 14. Distance L
1 can be made smaller than 75 μm, so that the reflected light P2 from the disk
The light is scattered at 0c and is not reflected again to return to the optical system.

As shown in FIG. 2B, all of the laser beams P having a spread angle of α must be reflected by the reflecting surface 14a of the mirror 14.

As an example, the substrate thickness (height of the active layer 10a) h2 of the laser chip 10 is 90 μm, the height H of the cut portion 14b at the tip of the mirror 14 is 80 μm, and the spread angle α of the laser beam P is 40 °. In this case, the distance L4 between the cut end portion 14b of the mirror 14 and the front-side light emitting end surface 10b of the laser chip 10 must be less than 27 μm.

FIG. 3 shows a third embodiment according to the present invention.

In this embodiment, even when the distance L1 between the front-side light emitting end face 10b of the laser chip and the position where the laser beam P is reflected by the mirror 12 is 75 μm or more in the first embodiment, the reflected light from the disc is not limited. Are not reflected on the light emitting end face of the laser chip.

According to the present invention, the submount 11 is provided with the rough surface portion or the low-light reflection film 100 at the position where the reflected light P2 from the disk is irradiated, thereby providing the reflected light P2.
Or the intensity of the reflected light of the reflected light P2 can be reduced.

However, the distance L3 between the tip of the mirror 12 and the front-side light emitting end face 10b of the laser chip 10 is such that the laser beam P having a certain divergence angle is
It must be shorter than the distance to intersect with b.

FIG. 4 shows a fourth embodiment according to the present invention.

This embodiment is different from the second embodiment in that the front side light emitting end face 10b of the laser chip 10 and the laser beam P
Even if the distance L1 from the position where the light is reflected by the mirror 14 is 75 μm or more, the light reflected from the disk is not reflected by the light emitting end face of the laser chip.

In this embodiment, the submount 13
By providing the rough surface portion or the low light reflection film 100 at a position where the reflected light P2 from the disk is irradiated, the reflected light P2 can be scattered or the reflected light intensity of the reflected light P2 can be reduced.

Also in this embodiment, the distance L4 between the cut end 14b of the mirror 14 and the laser chip 10b is
All of the laser beams P having a certain divergence angle must have a distance that can be reflected by the reflection surface 14a of the mirror 14.

FIG. 5 shows a fifth embodiment according to the present invention.

This embodiment uses a mirror 15 having a shape in which the tip is not cut off in the fourth embodiment.

In this embodiment, the mirror 15 is provided with a rough surface portion or a low light reflection film 101 at a position where the reflected light P2 from the disk is irradiated, so that the reflected light P2 is scattered or reflected. The intensity of the reflected light is reduced so that the light is not reflected again on the front side light emitting end face 10b of the laser chip 10.

Also in this embodiment, the distance L3 between the tip of the mirror 15 and the front-side light emitting end face 10b of the laser chip 10 is the distance until the laser beam P having a certain divergence angle crosses the submount surface 13b. Must be shorter than

FIG. 6 shows a sixth embodiment according to the present invention.

This embodiment is an embodiment in which the polarity is opposite to that of the laser chip described above, that is, the thickness h4 of the growth layer (the height of the active layer 10a) of the laser chip 10 is about 10 μm.

The reflected light P2 from the disk is radiated and scattered on the electrode surface 10c of the laser chip 10, while the other reflected light P1 is reflected by the reflecting surface 16a of the mirror 16 and the light on the front side of the laser chip 10 The light is reflected again by the emission end face 10b and returned to the optical system. Therefore, in the present embodiment, by providing the rough surface portion or the low light reflection film 101 on the mirror 16 at the position where the reflected light P1 from the disk is irradiated, the reflected light P1 is scattered or the reflected light P1 is scattered.
2, the intensity of the reflected light is reduced so as not to be incident again on the front-side light emitting end face 10b of the laser chip 10.

FIG. 7 shows a seventh embodiment according to the present invention.

This embodiment uses the mirror 17 having the shape and size as shown in the drawing in the sixth embodiment. In this embodiment, the reflected light P2 from the disk is reflected obliquely by the reflecting surface 17a of the mirror 17, so that the reflected light P2 does not return to the optical system again.

[0061]

When the laser apparatus of the present invention is used as a light source of an optical system for reading a disk, stable reading can be performed without causing a tracking error, noise, and the like.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a first embodiment showing a basic configuration of the present invention.

FIG. 2 is a diagram for explaining a second embodiment of the present invention.

FIG. 3 is a diagram for explaining a third embodiment of the present invention.

FIG. 4 is a diagram for explaining a fourth embodiment of the present invention.

FIG. 5 is a diagram for explaining a fifth embodiment of the present invention.

FIG. 6 is a diagram for explaining a sixth embodiment of the present invention.

FIG. 7 is a diagram for explaining a seventh embodiment of the present invention.

FIG. 8 is a diagram for explaining a conventional example.

FIG. 9 is a diagram for explaining a conventional example.

FIG. 10 is a diagram for explaining a conventional example.

FIG. 11 is a diagram for explaining a conventional example.

FIG. 12 is a diagram for explaining a conventional example.

FIG. 13 is a diagram for explaining a conventional example.

FIG. 14 is a diagram for explaining a conventional example.

[Explanation of symbols]

 1 to 7: laser chip 1a to 7a: active layer 1b to 7b: front side light emitting end face 4c: rough surface portion 5c: inclined portion 6c: low reflection material 7c: end surface protective film 8: stem rough surface portion 10: laser chip 10a: Active layer 10b: Front side light emitting end face 10c: Electrode 11: Submount 11a: Concave section 11b: Submount surface 12: Mirror 13: Submount 14: Mirror 14a: Mirror reflection surface 14b: Mirror 14 tip cut portion 15: Tip is 15 Uncut mirror 15a: mirror reflection surface 16, 17: mirror 16a, 17a: mirror reflection surface 100, 101: rough surface portion or low light reflection film P1, P2: reflection light from disk P1 ', P2': reflection light T1: Growth layer thickness t2: Substrate thickness

Claims (7)

[Claims] 1. A semiconductor laser device comprising, on a heat sink or a submount, at least a laser chip and a mirror disposed in front of a light emitting end face of the laser chip, wherein the laser chip has a light emitting end face. Wherein no return light is incident. 2. The heat sink or the submount,
2. The semiconductor laser device according to claim 1, further comprising a recess, wherein the laser chip is mounted in the recess. 3. The mirror according to claim 1, wherein the mirror is provided with an area for preventing light from re-entering the laser chip light emitting end face at a position where the return light is incident on the laser chip side end face. 13. The semiconductor laser device according to claim 1. 4. The light re-entry prevention area is formed by removing the mirror.
3. The semiconductor laser device according to item 1. 5. The semiconductor laser device according to claim 3, wherein said light re-inhibition region has a low reflection film formed thereon. 6. The semiconductor laser device according to claim 3, wherein the light re-inhibition region is a rough surface. 7. The semiconductor laser device according to claim 1, wherein a return light incident surface of the mirror is in a direction in which return light does not enter the laser chip light emitting end surface.