JPS63305580A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To improve recording density of an optical recording and reproducing device, by forming insulation grooves on both sides of a current narrowing electrode in the vicinity of at least one side of output terminal planes so that they range from an upper surface of a semiconductor laser to a position beyond its active layer. CONSTITUTION:Insulation grooves 14 are manufactured on both sides of a current narrowing electrode 7 in the vicinity of a forward output terminal plane 10 so that they range from the forward output terminal plane 10 to a position beyond an active layer 4, that is, in so depth that they attain to a substrate 2 from an electrode 12. Further, they are provided with fine processing by a reactive ion beam sputtering method so that they attain to both sides of the semiconductor laser 1. Hence, a spot of beams running parallel to the active layer 4 can be compressed to be 1mum or so, and also recording density of an optical and reproducing device can be upgraded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser having a light beam focusing function and used in optical recording/reproducing devices and the like.

(Prior Art) Conventionally, this type of semiconductor laser has a structure as shown in FIG. 2, in which 1 is a semiconductor laser, 2 is a substrate, 3 is a lower cladding layer, 4 is an active layer, and 5 is an upper layer. The cladding layer 10 is the front output end face. In FIG. 2, the shape of the light spot A is in the direction Wp parallel to the active layer 4 near the front output terminal 0.
is larger than the direction Ws perpendicular to the active layer 4, and the axial ratio is 2.5:l.
It had reached a certain level. For this reason, conventional optical heads use a shaping prism to form a circular light spot.

Furthermore, the optical head proposed by the authors in Japanese Patent Application No. 61-218097 as a future type optical head to improve the performance of optical disk devices has a structure as shown in FIG. 20 in close proximity. The optical head 21 is mounted on a slider 24 attached to a load spring 23 on an arm 22 that can move at high speed in the radial direction of the optical recording medium 20.
The spacing between the optical head 21 and the optical recording medium 20 is maintained at a constant value determined by the load of the load spring 23, the shape and weight of the slider 24, and the running speed of the optical recording medium 20. In this structure, the distance between the optical head 21 and the optical recording medium 20 is 1μ.
m, so a shaping prism for realizing a circular light beam cannot be used. Figure 3(b) shows the first part of the optical head.
FIG. 3(C) is a configuration diagram showing an example of the configuration of the optical head.
In this diagram, an optical head 21 is divided into a semiconductor laser 1 and a photodetector 30 by a separation groove 11 having a depth of several μm that reaches a substrate 2. 4 is an active layer, and 6 is an insulating layer. 7 is a current confinement electrode, and 31 is a light receiving section. According to FIG. 3(b), the light beam B from the front output end face 10 of the semiconductor laser 1 is reflected by the optical recording medium 20, and the reflected light C
returns to the semiconductor laser 1, and the light output (1!L combined resonance signal output) D at that time is detected by the light receiving section 31. Figure 4 (a
) and (b) show the spot diameter near the front output end face 10 of the light beam B of the conventional semiconductor laser shown in the first configuration example.

FIG. 4(a) shows the full width at half maximum, and FIG. 4(b) shows the 1/e2 diameter, the vertical axis shows the spot diameter, and the horizontal axis shows the distance from the front output end surface 10. In the figure, FWHM is the full width at half maximum. , The curve shown by ■ shows the theoretical value at 25 @, the curve shown by ■ shows the theoretical value at 10'', O is perpendicular to the active layer 4, ・One is the theoretical value at the time of the active layer 4
The actual measured values are shown in the parallel direction. From this, since the flying height, that is, the distance between the optical head 21 and the optical recording medium 20 is about 1 μm as shown by the arrow in the figure, the active layer It can be seen that the optical spot diameter becomes larger in the direction parallel to 4 (track density direction).

The second configuration example shown in FIG. 3(C) has a waveguide lens 40 at the tip, which reduces the light beam spot E on the optical recording medium (not shown) and improves the recording density. Can be done. In the figure, 41 is an etched mirror surface formed by microfabrication technology, which is in contact with a buffer layer 42 (for example, 5i02) forming the waveguide lens 40 and a waveguide layer 43 (for example, glass 7059). 44 is a Luneburg lens made of a dielectric material with a higher refractive index than the waveguide layer 43 (for example, S
IN), and has a circular circumference and a semicircular surface.

Furthermore, FIG. 5 shows a third configuration example of a semiconductor laser with a light focusing function, as described in S. Mukai et al.: Monollth
lc integratlon ora 1ens I
n5ide a diode-1aser cavit
yror-beam convergence'', Ap
pl, Phys, Lett, 47° (3) l, p
, 188.1985. 50 is a main part of the semiconductor laser 1 called a mode selector; 51
52 is a waveguide portion, and 52 is a lens portion that narrows the width of the upper cladding layer 5 of the active layer 4.

(Problems to be Solved by the Invention) However, according to the above conventional example, in the first configuration example, as is clear from FIGS. 4(a) and 4(b), the linear density is direction, parallel to the active layer 4,
That is, since the optical spot diameter is large in the track density direction, the track recording density decreases, and in the second configuration example, it is difficult to fabricate a minute Luneburg lens 44 of about several μm on the output end face of the semiconductor laser 1. In the third configuration example, it is difficult to realize a minute spot due to the aberration caused by the deviation between the shape design value and the processing value.Furthermore, in the third configuration example, it is difficult to realize a minute spot due to the structure, and the oscillation threshold increases. However, there was a problem that the lifespan was shortened. Therefore, there has been a problem in that it is not possible to improve the recording density of optical recording/reproducing devices using these semiconductor lasers.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a semiconductor laser in which a light spot parallel to an active layer can be compressed to about 1 μm, thereby improving the recording density of an optical recording/reproducing device.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a semiconductor laser having an optical beam focusing function in its active layer. An insulating groove was formed from the top surface to a position beyond the active layer.

(Function) According to the present invention, an insulating groove is formed on both sides of the current confinement electrode in the vicinity of at least one output end face of the semiconductor laser from the top surface of the semiconductor laser to a position beyond the active layer, so that a light beam is directed parallel to the active layer. It is possible to suppress the spread of

(Example 1) FIG. 1(a) is a perspective view showing a first embodiment of a semiconductor laser according to the present invention, and FIG. 1(b) is a perspective view taken in the direction of the arrow 1-1 in FIG. In the cross-sectional view, parts having the same configuration as the conventional one are denoted by the same reference numerals. In the figure, 1 is a rectangular parallelepiped-shaped semiconductor laser, 2 is a substrate made of n-type gallium arsenide (n-GaAs), and 3 is made by laminating n-type gallium aluminum arsenide (n-GaAIAs) on the top surface of the substrate 2. This is the lower cladding layer. 4 is an active layer formed by laminating gallium aluminum arsenide (GaAIAs) on the lower cladding layer 3, and has a light focusing function. 5 is an upper cladding layer formed by laminating p-type gallium aluminum arsenide (p-GaAIAs) on the active layer 4; 6 is silicon dioxide (Si02);
), 7 is a current confinement electrode into which current is injected, and is formed with a constant width on the upper center side of the semiconductor laser 1 from the front output end face 10 to the rear output end face 13. . 9 is a layer of gallium on the upper cladding layer 5:
This is a cap layer formed by laminating (GaAs). Also,
8 is an electrode provided on the lower surface of the substrate 2, and 12 is an electrode provided on the upper surface of the semiconductor laser 1. 14 is an insulating groove provided in the active layer 4 to suppress the spread of the light beam in the parallel direction;
On both sides of the current confinement electrode from the front output end face 10 in the vicinity of the front output end face 10, there is a top surface (i.e., a depth of several μm extending from the electrode 12 to the substrate 2), and further so as to reach both sides of the semiconductor laser 1. , manufactured by microfabrication using reactive ion beam sputtering. Further, in order to prevent oxidation and deterioration of the semiconductor 1, the insulating groove 14 is filled with a substance 15 having a refractive index lower than that of the active layer 4 (e.g. resist coating, 8102M with a thickness of about 200 to 300 nm). It is.

6(a), 6(b), and 6(c) show the shape of a light spot at the front output end face 10 of the semiconductor laser 1 with the above configuration, and FIG. 6(a) is a contour map of the light output, and FIG. 6
Figure (b) shows the shape of the light spot in the direction parallel to the active layer 4.
Figure (e) shows the shape of a light spot in the direction perpendicular to the active layer 4. On the other hand, Fig. 7 (a), (b), (c)
, is the rear output end surface 13 in which the insulating groove 14 is not formed.
The figure shows the shape of the light spot. As can be seen from the contour map of the light output in FIG. 7(a), the light spot is elliptical and has two peaks. In addition, FIG. 7(b) shows the active layer 4
The shape of the light spot in the direction parallel to the active layer 4 is shown in FIG. 7(c).
The shape of the light spot is perpendicular to . Furthermore, Fig. 8 (a
) and (b) show the optical spot diameter in the optical axis direction on the front output end face 10 side, where FIG. 8 (a> is the full width at half maximum, and FIG. 8 (b) is the 1/e2 diameter. 4 (a) and (b), O is the actual DI value in the direction perpendicular to the active layer 4, ・, * is the actual measured value in the direction parallel to the active layer 4, FWHM is the full width at half maximum, ■ is 25 @ The theoretical value at the time of , ■ indicates the theoretical value at the time of 10@.

As explained above, according to the first embodiment, the insulation groove 1
4 on both sides of the current confinement electrode 7, the convergence effect of the light beam is greatly improved, and it is also sufficient even when the flying height, that is, the distance between the optical head and the optical recording medium is 1 μm. It is available for use. Of course, an insulating groove may also be provided near the rear output end face 13.

(Example 2) FIG. 9 is a top view showing a second example of the semiconductor laser 1 according to the present invention, and the difference from the configuration of the first example lies in the shape of the current confinement electrode 7. That is, the current confinement electrode 7
The width is wide at the center and narrow near both the front output end face 10 and the rear output end face 13, and the width shape changes in a step-like manner, and the wide part is approximately 2/3 of the length of the entire current confinement electrode 7. It has become.

Further, the insulating groove 14 is formed on the front output end face 10 side.

10(a), (b), and (c) show the shape of the optical spot on the front output end face 10 side of the semiconductor laser 1 according to the second embodiment, and FIG. 10(a) shows the contour lines of the optical output. In the figure, it can be seen that it is approximately circular.

10(b) shows the shape of a light spot in a direction parallel to the active layer 4, and FIG. 10(e) shows a shape of a light spot in a direction perpendicular to the active layer 4. Furthermore, Fig. 11(a) and (b) show the spot diameter in the optical axis direction, Fig. 11(a) is the full width at half maximum, and Fig. 11(b) is the 1/e2 diameter, as shown in the figure. The symbols are the same as in FIGS. 8(a) and (b).

According to the embodiment of this section 2, the same effect as the first embodiment,
As is clear from FIG. 10(a), a substantially circular light spot with a diameter of about 1 μm can be realized, and the semiconductor laser is stable and has a low threshold value.

(Embodiment 3) FIG. 12 is a top view showing a third embodiment of the semiconductor laser according to the present invention. be. That is, the width of the current confinement electrode 7 is wide at the center as in the second embodiment and narrow at the front output end face 10 and rear output end face 13 sides, but the width shape changes into a tapered shape. Further, the insulating groove 14 is formed on the front output end face 10 side.

13(a), (b), and (c) show the shape of the optical spot on the front output end face 10 side of the semiconductor laser 1 according to the embodiment of Section 3, and FIG. 13(a) is a contour diagram of the optical output. 13(b) shows the shape of a light spot in a direction parallel to the active layer 4, and FIG. 13(C) shows the shape of a light spot in a direction perpendicular to the active layer 4. On the other hand, Fig. 14(a),
(b) and (c) show the shape of the light spot on the rear output end face 13 side where the insulating groove 14 is not formed, and Fig. 14 (
As can be seen from the contour map of optical output in a), Fig. 7(a)
Similarly, the light spot has long days and twin peaks. FIG. 14(b) shows the shape of the light spot in the direction parallel to the active layer 4.
Figure (C) shows the tip spot shape in the direction perpendicular to the active layer 4. Moreover, FIGS. 15(a) and 15(b) show the spot diameter in the optical axis direction on the front output end face 10 side, and FIG.
) is the full width at half maximum, and FIG. 15(b) is the 1/e2 diameter, and the symbols shown in the figure are the same as those in FIGS. 8(a) and (b).

According to the embodiment of Section 3, the same functions and effects as the first and second embodiments can be obtained, and the diameter of the light spot in the direction parallel to the active layer is larger than that of the second embodiment. but,
The object of the present invention can be fully achieved, and furthermore, by forming the current confinement electrode 7 in a tapered shape, the oscillation threshold can be made smaller (about 70 mA).

(Embodiment 4) FIG. 16 is a top view showing an embodiment of an optical head using a semiconductor laser according to the present invention. The insulating groove 14 is provided on the front output end face 10 side, and the insulating groove 14 further divides the semiconductor laser 1 in the center and the photodetectors 'rr16 and 17 on both sides, and the current confinement electrode 7 is provided as in the third embodiment. It is formed into a tapered shape. Also, on the lower surface side of the electrode 12, which is the upper surface of the photodetector 16.
(indicated by 9 in FIG. 1) is provided.

To explain the operation of the optical head with the above configuration, first,
Semiconductor laser 1 is injected with current through current confinement electrode 7.
By emitting light, the light beam B emitted from the front output end face 10 is reflected by the optical recording medium 20, and the reflected light is detected by the photodetectors 16 and 17.

According to the embodiment of Section 4, the insulating groove 1 is provided on the front output end face 10 side for suppressing the spread of the light beam in the direction parallel to the active layer.
4, and furthermore, the semiconductor laser 1 with the current confinement electrode 7 formed in a tapered shape is used as the light source of the optical head, so a circular minute light spot with a diameter of about 1 μm FU can be realized, and optical recording is possible. The recording surface density of the reproducing device can be increased.

(Effects of the Invention) As explained above, according to the present invention, insulating grooves are formed on both sides of the current confinement electrode near at least one output end face from the top surface of the semiconductor laser to a position beyond the active layer. The spread of the light beam in the direction parallel to the active 7W is suppressed near the end face, and the diameter is approximately 1μ in the same direction as the direction perpendicular to the active layer.
It is possible to realize a small circular light spot of about 100 m in diameter, and it is stable.
A practical semiconductor laser with a low threshold value can be provided. Therefore, if the present semiconductor laser is used as a light source of an optical head, there is an advantage that an optical recording/reproducing device with a high recording surface density can be provided.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view showing a first embodiment of a semiconductor laser according to the present invention, and FIG. 1(b) is an I
- A sectional view taken in the direction of the arrow at part 1, Figure 2 is an explanatory diagram for explaining the shape of a light spot of a conventional semiconductor laser, and Figure 3 (a) is a perspective view showing the state of use of a conventional optical head. , 3rd
FIG. 3(b) is a configuration diagram showing a first configuration example of a conventional optical head; FIG. 3(c) is a configuration diagram showing a second configuration example of a conventional optical head; FIG. 4(a), (b) shows the spot diameter in the optical axis direction of a conventional semiconductor laser, (a) shows the full width at half maximum, (b) shows the 1/e2 diameter, and Fig. 5 shows the spot diameter of the conventional semiconductor laser. A configuration diagram showing an example of the configuration of the semiconductor laser shown in FIG. 3,
6(a), (b), and (c) show the shape of a light spot on the front output end face side of the semiconductor laser according to the first embodiment, and FIG. 6(a) is a contour diagram of the front output, and FIG. (b) is a diagram showing the shape of a light spot in a direction parallel to the active layer, (c) is a diagram showing a shape of a light spot in a direction perpendicular to the active layer, and FIG.
), (b), and (c) show the shape of the optical spot on the rear output end face side of the semiconductor laser according to the first embodiment, where (a) is a contour diagram of the optical output, and (b) is a contour diagram of the optical output. Figure 8(c) shows the shape of a light spot in the direction parallel to the active layer; Figure 8(a) shows the shape of the light spot in the direction perpendicular to the active layer.
, (b) shows the spot diameter in the optical axis direction of the semiconductor laser according to the first embodiment, (a) shows the full width at half maximum, (b) shows the 1/e2 diameter, FIG. 9 is a top view showing the second embodiment of the semiconductor laser according to the present invention, and FIGS. 10(a), (b), and (c) are views of the front output end face side of the semiconductor laser according to the second embodiment. The shape of the tip spot is shown; (a) is a contour diagram of the optical output; (b) is a diagram showing the shape of the light spot in the direction parallel to the active layer; (C) is a diagram showing the shape of the light spot.
11 is a diagram showing the shape of a light spot in the direction perpendicular to the active layer.
Figures (a) and (b) show the spot diameter in the optical axis direction of the semiconductor laser according to the second embodiment, where (a) shows the full width at half maximum, and (b) shows the 1/e2 diameter. Figure 12
The figure is a top view showing a third embodiment of a semiconductor laser according to the present invention, and FIGS. 13(a), (b), and (c) show the shape of a light spot on the front output end face side according to the third embodiment. , Figure (a) is a contour diagram of optical output, Figure (b) is a diagram showing the shape of a light spot in a direction parallel to the active layer, and Figure (c) is a diagram showing the shape of a light spot in a direction perpendicular to the active layer. , Figure 14 (
a), (b), and (c) show the shape of the optical spot on the rear output end face side of the semiconductor laser according to the third embodiment, where (a) is a contour diagram of the optical output, and (b) is a contour diagram of the optical output. Figure 15 (C) shows the shape of a light spot parallel to the active layer; Figure 15 (C) shows the shape of a light spot perpendicular to the active layer;
a) and (b) show the spot diameter in the optical axis direction of the semiconductor laser according to the third embodiment, where (a) shows the full width at half maximum, and (b) shows the 1/e2 diameter. , FIG. 16 is a top view showing an embodiment of an optical head to which a semiconductor laser according to the present invention is applied. In the figure, 1... semiconductor laser, 2... substrate, 3...
Lower cladding layer, 4... Active layer, 5... Upper cladding layer, 6... Insulating layer, 7... Current confinement electrode, 8.
DESCRIPTION OF SYMBOLS 12... Electrode, 9... Cap layer, 10... Front output end surface, 13... Rear output end surface, 14... Insulating groove.

Claims (3)

[Claims] (1) A semiconductor laser having an optical beam focusing function in its active layer, characterized in that insulating grooves are formed on both sides of a current confinement electrode in the vicinity of at least one output end face from the top surface to a position beyond the active layer. laser. (2) The semiconductor laser according to claim 1, wherein a substance having a refractive index lower than the refractive index of the active layer is embedded in the insulating groove. (3) The semiconductor laser according to claim 1 or 2, wherein the shape of the current confinement electrode is narrow near the output end face and wide at the center.