JPH0730206A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To downsize a semiconductor laser device, prevent errors in the alignment accuracy and shape accuracy and accurately detect a control signal and a recording information signal. CONSTITUTION:An integrated element 25 is formed by monolithically forming a semiconductor laser 11, a signal detecting photodetector 16 and a photodetector 15 for monitoring the laser beam power. A transparent block 21 is formed of a diffraction-type element 20 and a reflecting film 22. The integrated element 25 and the transparent block 21 are fixed permitting the diffraction-type element 20 to position on the optical path of the beam 13 emitted from the semiconductor laser 11, the reflecting film 22 to position on the optical path of the beam 17 which is branched by the diffraction-type element 20 and is permitted to return from the external, and the signal detecting photodetector 16 to position on the optical path of the beam reflected by the reflecting film 22. The photodetector 15 for monitoring the laser beam power is provided on the optical path of the beam emitted from other part of the semiconductor laser 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of irradiating a light beam for reading optical information and detecting the light output of the incident light beam. In particular, the present invention is used with an objective lens to construct an optical pickup. To obtain a semiconductor laser device.

[0002]

2. Description of the Related Art In general, an optical pickup irradiates an optical recording medium such as an optical disc with a light beam and detects a focus / tracking error signal to perform a predetermined control to detect a signal light from the optical recording medium. Information is read by doing so. Such an optical pickup is made up of optical components such as a semiconductor laser, a photodetector, a beam splitter, and an objective lens. Normally, each optical component is manufactured as an independent component, and the optical path of these components is adjusted. It is manufactured by assembling in the state.
Therefore, due to the large number of optical components, it takes a lot of man-hours to adjust the optical path, and it is difficult to reduce the cost.
Also, because the individually manufactured optical components are assembled,
There is also a limit to the size reduction of the entire optical pickup.

Therefore, a semiconductor laser device as shown in FIG. 3 has been proposed (Japanese Patent Application No. 01-270382). This semiconductor laser device includes a semiconductor substrate 5 such as a silicon substrate.
A semiconductor laser 52, a photodetector 45 for signal detection, a photodetector 54 for laser light output monitoring, and the like are integrated on the structure 1 as follows. That is, the photodetector 45 for signal detection is formed on the upper surface layer of the semiconductor substrate 51, and the 45 ° inclined mirror surface 53 for deflecting the laser beam is formed by etching or the like. A photodetector 54 for monitoring the light output is formed on the surface layer. Next, the chip-shaped semiconductor laser 52 is bonded to a predetermined position with the highest possible accuracy.
Thus, the functions of the semiconductor laser 52, the signal detection photodetector 45, and the laser light output monitor photodetector 54 are integrated. A coating film 56 as a reflecting film is formed on the photodetector 54, and a coating film 55 as a reflecting film is formed on the upper surface of the semiconductor laser 52 and the side surfaces other than the laser beam emitting surface.

In addition to these components, an optical pickup is constructed by externally disposing an objective lens 44 and a diffractive element 43 for splitting light. In this optical pickup, the emission laser beam 57 emitted from the semiconductor laser 52 is reflected by the coating film 56, and the reflected emission laser beam 58 passes through the objective lens 44 and then is irradiated onto the optical disc 42. The laser beam reflected from the optical disk 42 changes its direction by the diffractive element 43 and is captured by the photodetector 45, where the recording information signal is detected.

[0005]

By the way, in the conventional semiconductor laser device, the semiconductor laser 52 is attached by bonding, but there is a limit in the bonding accuracy, and an error easily occurs in the formation position of the semiconductor laser 52. Further, since there is a limit to the technique for forming the tilted mirror surface 53 by etching or the like, an error is likely to occur between the manufacturing accuracy of the tilted mirror surface and the shape accuracy of the tilted mirror surface 53 itself. If the former error exists, the distance between the emission point of the semiconductor laser 52 and the light beam deflection position (reflection position) of the tilted mirror surface 53 varies. On the other hand, when the latter error exists, the wavefront aberration of the beam emitted from the semiconductor laser 52 deteriorates. Further, the following problems occur due to such bonding accuracy error, distance variation, or wavefront aberration deterioration. That is, the shape of the focused beam on the photodetector 54 is disturbed, the position of the focused beam is displaced, or the wavefront aberration of the focused spot for reading on the optical recording medium. Of the focus / tracking error signal, which has a serious adverse effect on the detection of the control signal and the recording information signal based on the focus / tracking error signal.

The present invention has been made to solve the above-mentioned problems of the conventional technique, and of course, it is possible to reduce the size, and it is difficult for an error to occur between the manufacturing position accuracy and the shape accuracy, which makes it possible to control. It is an object of the present invention to provide a semiconductor laser device capable of accurately detecting the above signal and recorded information signal.

[0007]

A semiconductor laser device of the present invention is a return light beam that returns the light beam emitted from the semiconductor laser from the outside through the diffractive element. Is branched by the diffractive element with the light beam emitted from the semiconductor laser to be incident on the photodetector for signal detection, while the light beam emitted from another portion of the semiconductor laser is used for laser light output monitoring. A semiconductor laser device for capturing and monitoring with a photodetector, wherein the semiconductor laser, the signal detection photodetector, and an integrated element in which the laser light output monitoring photodetector is monolithically formed, and the diffraction type The integrated element and the transparent block, the element and a transparent block having a reflective film for reflecting the returning light beam branched by the diffractive element toward the photodetector for signal detection. And the diffractive element is positioned on the optical path of the light beam emitted from the semiconductor laser, and the reflective film is positioned on the optical path of the light beam branched from the diffractive element and returned from the outside. Since the signal detecting photodetector is fixedly placed on the optical path of the light beam reflected by, the above object is achieved by that.

In this semiconductor laser device, the laser light output monitor photodetector is preferably provided on the optical path of the light beam emitted from another portion of the semiconductor laser. In addition, one or more of the diffracted light generated when the light is split by the diffractive element on the transparent block is reflected by the reflective film, and the reflected light is guided to the photodetector for signal detection. can do.

[0009]

According to the present invention, an integrated element in which a semiconductor laser, a photodetector for signal detection and a photodetector for laser light output monitor are monolithically formed, and a transparent block on which a diffractive element and a reflection film are formed Is a diffraction element on the optical path of the light beam emitted from the semiconductor laser, the reflection film is reflected on the reflection film on the optical path of the light beam branched from the semiconductor element and returned from the outside. The photodetectors for signal detection are fixedly mounted on the optical path of the light beam. In this configuration, the laser light output monitor photodetector is provided on the optical path of the light beam emitted from another portion of the semiconductor laser.

Therefore, the semiconductor laser, the photodetector for signal detection, and the photodetector for laser light output monitoring are monolithically formed, so that the size can be reduced. Further, the mutual positional relationship among the semiconductor laser, the photodetector for signal detection, and the photodetector for laser light output monitoring provided on the integrated element can be determined with the same high precision as in the semiconductor manufacturing process. As for the transparent block, a diffraction element forming surface for forming the diffraction element of the transparent block and a reflection film forming surface for forming the reflection film of the transparent block are formed by using a technique for producing an optical component such as a prism. The alignment accuracy can be improved by producing the angle accuracy with respect to and with high accuracy and then manufacturing the diffractive element on the surface on which the diffractive element is formed by the semiconductor manufacturing technique. Due to this improvement in alignment accuracy, the light beam reflected by the reflecting surface can be incident on the photodetector for signal detection with high positional accuracy.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a semiconductor laser device 10 of this embodiment.
It is a front view which shows 0. This semiconductor laser device 100
Is a semiconductor laser 11 having a resonator in the lateral direction formed on a substrate 10 such as a GaAs substrate.
The light beam 13 is emitted from the resonator end face 12. A laser light output monitoring photodetector 15 is formed on the substrate 10 adjacent to the other (lower) resonator end face 14 of the semiconductor laser 11 and adjacent to the resonator end face 14, and the photodetector is also provided. A photodetector 16 for signal detection, which is composed of, for example, a multi-divided photodiode, is formed adjacent to 15. That is, on the substrate 10, the semiconductor laser 1
1. The laser light output monitor photodetector 15 and the signal detection photodetector 16 are monolithically manufactured, and the relative manufacturing position of the emission point of the semiconductor laser 11 and the signal detection photodetector 16 is They are integrated so as to obtain high precision, and an integrated element 25 is formed by these. Separately from the substrate 10, a transparent block 21 made of, for example, glass, resin, or the like is fixedly provided on the resonator end face 12 of the integrated element 25 by, for example, bonding. The transparent block 21 has a diffractive element forming surface 23, which is an end surface opposite to the resonator end surface 12, and a transparent block 21.
Of the emitted light 13 incident from the end face on the cavity end face 12 side of
And a diffractive element 20 for branching the incident light (diffracted light) 17 used for detection reflected from an optical disk (not shown) provided above the transparent block 21. Further, the transparent block 21 has a reflective film formation surface 24, which is a partial region of one side surface thereof,
The reflective film 22 is formed by vapor deposition or the like. The reflective film 22 reflects the diffracted light 17 obtained by passing through the diffractive element 20, and focuses the reflected light on the signal detection photodetector 16 of the integrated element 25. Has become.

As for the angle accuracy between the surface of the diffractive element forming surface 23 and the reflecting film forming surface 24 of the transparent block 21 described above, a required accuracy amount is secured by polishing or the like as in the case of manufacturing an optical component such as a prism. It is considered possible. In consideration of mass production, it is possible to use a bar-shaped one capable of forming a plurality of or a large number of transparent blocks 21 and adopt a method of cutting after polishing all necessary surfaces. It is possible. Further, if the required angle accuracy can be obtained by injection molding, injection molding may be adopted. If it is adopted, the diffractive element 20 is used in the injection mold.
By setting the means for forming the above and performing the injection molding in that state, both the diffractive element 20 and the diffractive element 20 can be manufactured in one step (molding). When the diffractive element is manufactured in a separate step, the accuracy of the formation position of the diffractive element 20 can be ensured by the positioning accuracy of the semiconductor manufacturing process. Further, regarding the production of the diffractive element 20, in consideration of mass production, a bar-shaped element may be used to collectively form the element, or a forming method may be performed by molding if the required accuracy of the die is obtained. .

When the integrated element 25 and the transparent block 21 are fixedly mounted, the integrated element 2 is so arranged that the light 13 emitted from the semiconductor laser device 100 is incident on the diffractive element 20.
5 and the transparent block 21 are aligned with each other, and then the incident light (diffracted light) 17 used for detection is the photodetector 1 for signal detection.
The transparent block 21 is placed on top of 6 so that a predetermined light-collecting state is achieved.
Rotate to match. As a result, the optical path length between the diffraction type element 20 and the emission point of the semiconductor laser 11 or the optical path length between the diffraction type element 20 and the signal detection photodetector 16 is
Within the error range of the accuracy of the accuracy in the semiconductor manufacturing process or the manufacturing accuracy of the optical component, whichever is worse (within the error range of the micron unit), the value can be set as designed.

FIG. 2 shows a front view (cross-sectional view) of an example of packaging the present semiconductor laser device 100 having such a structure. The integrated element 25 and the transparent block 21 described above
Are attached to the fixing substrate 31 and are fixed to the package substrate 30. Furthermore, the whole is cap 2
It is surrounded by 6 and is exposed so that the laser light can enter and exit only the portion of the diffractive element 20. Wiring, element terminals, etc. are omitted in this figure.

An optical pickup can be configured by adding a finite conjugate system objective lens to the semiconductor laser device 100 of the present embodiment having the above configuration.

The operation of the optical pickup as an optical pickup will be described below.

When the light beam 13 is emitted from the semiconductor laser 11 in the semiconductor laser device 100 of the present embodiment, the light beam 13 passes through the diffractive element 20 on the transparent block 21 as it is, and then enters the optical path. The light is focused on an optical disc (not shown) through an arranged objective lens (not shown). The reflected light from the optical disk passes through the objective lens again and is incident on the diffractive element 20 again.
Since 0 acts as an optical branching element, the light beam 13 including the focus / tracking error signal and the recording information signal is
Here, the diffracted light 17 is separated.

The diffracted light 17 is reflected by the reflective film 22 formed in a partial region of the side surface of the transparent block 21, and is condensed on the signal detecting photodetector 16 at the designed position for the above-mentioned reason. . The signal detection photodetector 16 detects a control focus / tracking error signal and a recording information signal based on the incident light. In addition, the semiconductor laser 11
The optical output of the monitor is the photodetector 1 for the monitor formed adjacently.
Monitored at 5.

[0020]

As described above, according to the present invention, since the optical components of the semiconductor laser, the signal detecting photodetector and the laser light output monitor photodetector are formed monolithically, the overall size is reduced. It is possible to improve the relative positional accuracy of each optical component. Further, since it does not include an element such as a 45-degree tilt mirror by etching or the like, which is difficult to produce in manufacturing position accuracy and shape accuracy, it is advantageous in manufacturing. Further, by accurately producing the diffractive element formation surface and the reflection film formation surface of the transparent block, the optical path can be easily adjusted at the time of assembling the semiconductor laser device, and the deviation from the optical path design can be reduced. , When the signal is detected, the light can be focused on the predetermined position of the photodetector with high accuracy.
There is an effect that adverse effects such as offset are less likely to occur.

[Brief description of drawings]

FIG. 1 is a front view showing a semiconductor laser device according to an embodiment of the present invention.

FIG. 2 is a front view (cross-sectional view) showing a state in which the semiconductor laser device of FIG. 1 is packaged.

FIG. 3 is a sectional view showing an example of a conventional semiconductor laser device.

[Explanation of symbols]

 10 Substrate 11 Semiconductor Laser 12 Resonator End Face of Semiconductor Laser 13 Light Beam (Emitting Light) 14 Resonator End Face of Semiconductor Laser 15 Laser Light Output Monitor Photo Detector 16 Signal Detection Photo Detector 17 Light Beam (Diffracted Light) 20 Diffractive element 21 Transparent block 22 Reflective film 23 Diffractive element forming surface 24 Reflective film forming surface 25 Integrated element 26 Cap 30 Package substrate 31 Fixing substrate 100 Semiconductor laser device

Claims (3)

[Claims] 1. A light beam emitted from a semiconductor laser is transmitted through a diffractive element to be emitted to the outside, and a returning light beam returning from the outside of the light beam is emitted from the semiconductor laser by the diffractive element. A semiconductor laser device in which the light beam emitted from another portion of the semiconductor laser is captured by a laser light output monitoring photodetector while being branched from the emitted light beam to be incident on the signal detection photodetector. The semiconductor laser, the photodetector for signal detection, and the photodetector for laser light output monitoring are monolithically formed into an integrated element, the diffractive element, and branched by the diffractive element. A transparent block formed with a reflective film for reflecting the returning light beam toward the signal detecting photodetector, wherein the integrated element and the transparent block are light beams emitted from a semiconductor laser. A diffractive element on the optical path of, the reflective film is positioned on the optical path of the light beam branched by the diffractive element and returned from the outside, and the signal is on the optical path of the light beam reflected by the reflective film. A semiconductor laser device fixed in a state where a photodetector for detection is positioned. 2. A photodetector for monitoring the laser light output,
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is provided on an optical path of a light beam emitted from another portion of the semiconductor laser. 3. One or a plurality of lights among the diffracted lights generated when the light is split by the diffraction type element on the transparent block are reflected by the reflection film, and the reflected lights are detected by the photodetector for signal detection. The semiconductor laser device according to claim 1, wherein the semiconductor laser device guides light to.