JPS61243964A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To make it unnecessary to adjust a position at assembling the titled device into an applied apparatus, and to make it small in size and simple by using a beam reflected by a triangular prism which has been fixed onto a photodetector, as an irradiating beam, and detecting a transmitting beam. CONSTITUTION:A beam 4 which is emitted from a laser diode chip 31 and is reflected by a slant face 27a of a triangular prism 27 transmits through a window glass 32 and an objective lens 5 and is made incident on an optical recording medium 6. On the other hand, the beam 4 which is reflected by the medium 6 is made incident on the slant face 27a, in a converging state, and made incident on a PIN diode 25 and detected, in a state that an astigmatism is generated by a difference of a refractive index between the prism 27 and air. In this way, when incorporating the titled device into an applied apparatus, it is made unnecessary to adjust a position between each parts, and it can be made small in size and simple.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device that performs beam irradiation and detection of an incident beam, and is particularly useful for use in an optical head.

[Summary of the invention]

The present invention integrates a semiconductor laser, a photodetector, and a beam splitter in a semiconductor laser device as described above,
Moreover, by providing the beam splitter with the function of generating astigmatism, it is possible to reduce the size and cost of the applied equipment.

[Conventional technology]

Optical heads used in optical recording and reproducing devices, etc.
Information is recorded and reproduced by irradiating an optical recording medium with a beam and detecting a modulated beam from the optical recording medium.

Further, since the optical head is used without contacting the optical recording medium, a focus servo is required. There are various focus error detection methods, but the astigmatism method is often used.

A semiconductor laser device is usually used in the optical head. FIG. 11 shows an optical head in which a conventional example of a semiconductor laser device is used.

In this optical head 1, a beam 4 emitted from a semiconductor laser 2 and reflected by a beam splitter 3 passes through an objective lens 5 and enters an optical recording medium 6.

The beam 4 reflected by the optical recording medium 6 and transmitted through the objective lens 5 and beam splitter 3 is transmitted through a semicircular cylindrical lens 7 and is detected by a photodetector 8 with astigmatism generated.
incident on the

That is, in this optical head 1, four optical components, ie, a semiconductor laser 2, a beam splitter 3, a cylindrical lens 7, and a photodetector 8, constitute a semiconductor laser device 9.

[Problem that the invention seeks to solve]

However, in such a semiconductor laser device 9, since the four optical components are spaced apart from each other, it is necessary to adjust the positions of these four optical components when assembling the optical head 1. Therefore, the optical head 1 is expensive.

Further, since the semiconductor laser device 9 requires many optical components as described above, the optical head 1 is large and expensive.

[Means for solving problems]

Semiconductor laser device according to the present invention! 21,43°46.51
．． 52 includes a photodetector 25 formed on the semiconductor substrate 24.47, at least one triangular prism 27.45.49 fixed on the photodetector 25, and a photodetector 25 formed on the semiconductor substrate 24.47; The beam 4 emitted from the semiconductor laser 31 and reflected by the triangular prism 27, 45, 49 is used as the irradiation beam, and the beam 4 emitted from the semiconductor laser 31 is used as the irradiation beam. 49 and this triangular prism 27
, 45.49 is detected by the photodetector 25.

[For production]

Semiconductor laser device according to the present invention 21.43°46.51
．． At 52, the irradiation of the beam 4 and the detection of the incident beam 4 are performed by an integrated optical component.

Moreover, if the beam 4 incident on the triangular prisms 27, 45.49 is in a convergent state, the triangular prisms 27, 45, 49
Astigmatism is generated in the incident beam 4 by passing through the beam, and the triangular prisms 27, 45, 49 have the function of generating astigmatism in addition to the function of a beam splitter.

〔Example〕

Hereinafter, first to fifth embodiments of the present invention will be described with reference to FIGS. 1 to 10.

1 and 2 show a first embodiment of the invention. In the semiconductor laser device 21 of the first embodiment, a silicon substrate 24 is fixed on a stem 23 having leads 22, and a P/N diode 25, which is a photodetector for signal detection, is mounted on the silicon substrate 24. A PIN diode 26, which is a photodetector for monitoring laser output, is formed.

A triangular prism 27 is fixed with an adhesive on the silicon substrate 24 at the position where these PIN diodes 25 and 26 are formed, and another silicon A substrate 28 is fixed. Further, a laser diode chip 31, which is a semiconductor laser, is mounted on the end of the silicon substrate 28 on the triangular prism 27 side. Note that the triangular prism 27 facing this laser diode chip 31
The slope 27a has a reflectance of about 50%, and the other slope 27b is coated with a total reflection coating and has a reflectance of 100%.

A cap 33 having a window glass 32 is mounted on the stem 23, and the above-mentioned optical system is hermetically sealed. Note that the PIN diode 25.
26 and the laser diode chip 31 and the leads 22 are connected by wires (not shown).

FIG. 3 shows an optical head using the semiconductor laser device 21 as described above. In this optical head 34, the laser diode chip 31 emits light into a triangular prism 27.
The beam 4 reflected by the slope 27 a passes through the window glass 32 and the objective lens 5 and enters the optical recording medium 6 .

It is reflected by the optical recording medium 6 and passes through the objective lens 5 and the window glass 32.
The beam 4 transmitted through the slope 27a is incident on the PIN diode 25.

By the way, the beam 4 reflected by the optical recording medium 6 enters the slope 27a in a convergent state, and there is a difference in refractive index between the triangular prism 27 and the air. For this,
The beam 4 enters the PIN diode 25 with astigmatism generated.

As a result, if the positional relationship between the laser diode chip 31 and the PIN diode 25 is determined so that the beam spot 35 of the beam 4 incident on the PIN diode 25 in a focused state has the shape shown in FIG. 4B, the PIN diode 2
A beam spot 35 having a shape as shown in FIG. 4A or C is formed on the beam spot 5 depending on the deviation from the focused state.

Therefore, by using a circuit as shown in FIG.
The focus error signal (A+C)−(
B+D), and a tracking error signal and a reproduction signal A+B+C+D can be obtained via the phase comparator 37 and adder 38, respectively.

In addition, if sufficient astigmatism cannot be obtained only by the refractive index difference between the triangular prism 27 and the air, a part of the triangular prism 27 may be shaved off as shown by the phantom lines in FIGS. 1 and 2. Accordingly, the cylindrical lens portions 41 and 42 may be formed in advance.

Further, in the semiconductor laser device 21 of this first embodiment, the first
As shown in the figure, the beam 4 emitted from the laser diode chip 31 passes through the slope 27a of the triangular prism 27 and is also incident on the PIN diode 26 either directly or after being reflected by the slope 27b. Therefore, the output of the laser diode chip 31 can be adjusted based on the output from the PIN diode 26.

In the semiconductor laser device 21 of the first embodiment as described above, the laser diode chip 31 emits light from the triangular prism 2.
The beam 4 reflected by the slope 27a of the laser diode chip 31 does not directly return to the laser diode chip 31. Therefore, the laser diode chip 31 generates less noise.

Furthermore, since the single triangular prism 27 functions as a beam splitter, the cost of this semiconductor laser device 21 is low.

Furthermore, since the PIN diodes 25 and 26 are formed on the same surface of the same silicon base Fi 24, these PIN diodes 25 and 26 are
The IN diodes 25, 26 can be formed simultaneously by lithography.

FIG. 6 shows a second embodiment of the invention.

The semiconductor laser device 43 of this second embodiment is similar to the first embodiment shown in FIG. It may have substantially the same configuration as the semiconductor laser device 21 in the example.

FIG. 7 shows a semiconductor laser device 43 of such a second embodiment.
2 shows the amount of signal obtained from the PIN diode 25 with respect to the distance that the optical recording medium 6 has moved in the optical axis direction of the beam 4 when used in an optical head. Note that this signal amount is determined by using optical glasses BK7 and 5Fil as the right-angle prisms 44 and 45, respectively, setting the height of the beam splitter to 1 crane, and using a lens with a finite magnification with an NA of 0.47 as the objective lens 5. Although not shown in FIG. 3, this is the result when a collimator lens with NAfJ<0.14 was used.

FIG. 8 shows a third embodiment of the invention.

The semiconductor laser device 46 of this third embodiment includes the formation of PIN diodes 25 and 26 and the laser diode chip 31.
are placed on an integrated silicon substrate 47, and two right angle prisms 48 having different refractive indexes are placed on an integrated silicon substrate 47.
．． The beam splinter composed of 49 is PI
The silicon substrate 4 is placed only on the N diode 25.
The structure may be substantially the same as that of the semiconductor laser device 21 of the already described first embodiment shown in FIG.

FIG. 9 shows a fourth embodiment of the invention.

The semiconductor laser device 51 of the fourth embodiment is fixed on a silicon substrate 24, and a PIN diode 26 for monitoring laser output is formed on the silicon substrate 28 on which the laser diode chip 31 is mounted. Except for this, the structure may be substantially the same as that of the semiconductor laser device 46 of the previously described third embodiment shown in FIG.

Therefore, in the semiconductor laser device 51 of this fourth embodiment, P
IN diode 26 is used as a bank monitor for laser diode chip 31.

FIG. 10 shows a fifth embodiment of the invention.

The semiconductor laser device 52 of this fifth embodiment has a PIN diode 25 formed on a silicon substrate 24.
The structure may be substantially the same as that of the semiconductor laser device 51 of the fourth embodiment shown in FIG. 9, except that the diode 26 is also formed.

〔Effect of the invention〕

Since the semiconductor laser device according to the present invention is an integrated optical component, there is no need to adjust the position of each component when incorporating it into the applicable equipment, and the cost of the applicable equipment can be reduced.

Further, since the triangular prism has both the function of a beam splitter and the function of generating astigmatism, when applied to a device that utilizes astigmatism, it is possible to downsize and reduce the cost of this device.

[Brief explanation of drawings]

Figures 1 to 1O show embodiments of the present invention.
Figure 2 is a side sectional view of the first embodiment, Figure 2 is a plan view of the main parts of the first embodiment, Figure 3 is a side view of the optical head to which the first embodiment is applied, and Figure 4 shows the beam spot. 5 is a block diagram showing the circuit system of the optical head shown in FIG. 3, FIG. 6 is a side sectional view of the second embodiment, and FIG. 7 is a diagram of the second embodiment. Waveform diagrams of signals obtained by the optical head to which the example is applied, and FIGS. 8 to 10 are side sectional views of the third to fifth embodiments, respectively. FIG. 11 is a side view of an optical hemometer to which a conventional example of the present invention is applied. ξ −In the symbols used in the drawings, 4−・−1−−−−−−−−−−−−・Beam 2t−
−−−−−−−−−−−−−−−−−・Semiconductor laser device 24−−−1・−・−−−−−−−−−−・Silicon substrate 25・・−−− −−−−−・−−１−−−−・
PIN diode 2'7'----・----1----・
...-triangular prism 31--------
------Laser diode chip 43-----
---・--Semiconductor laser device 45・---------1----------Right angle prism 46--
--------------Semiconductor laser device 47---
−−−−−−−−−−−・−−−−−Silicon substrate 49
−・−1−−−−−−−−−−−Right angle prism 51
．． 52-1111 --- Semiconductor laser device. A f3 C

Claims (1)

[Claims] A photodetector formed on a semiconductor substrate, at least one triangular prism fixed on the photodetector, and a semiconductor laser fixed on the semiconductor substrate. A beam emitted from the semiconductor laser and reflected by the triangular prism is used as an irradiation beam, and a beam incident on the triangular prism and transmitted through the triangular prism is detected by the photodetector. Semiconductor laser equipment.