JPS61243963A - 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 reflected beam of a thin film which is formed on the surface of a photodetector, as an irradiating beam, and detecting a transmitting beam. CONSTITUTION:On a substrate 24, a silicon substrate 31 is fixed so as to be inclined against the emitting surface of a laser diode chip 26, and on this substrate 31, a PIN diode 32 for detecting a signal is formed, and also, a thin film 33 whose optical transmittivity and reflection factor are 50%, respectively is formed on the surface. In such a state, a beam 4 which is emitted from the chip 26 and reflected by the thin film 33 transmits through a window glass 34 and an objective lens 5 and is made incident on an optical recording medium 6. Also, the beam which is reflected by the medium 6 and has transmitted through the lens 5, the glass 34 and the thin film 33 is made incident on the diode 32 and detected. In such a way, it is made unnecessary to adjust a position at assembling the titled device,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.

〔overview〕

In the semiconductor laser device as described above, the present invention integrates the semiconductor laser and the photodetector in a state where the photodetector is tilted with respect to the emission surface of the semiconductor laser, and also functions as a beam splitter. By forming a thin film containing the photodetector on the surface of the photodetector, it is possible to make the photodetector compact, low cost, highly reliable, and reduce the 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 the modulated beam from the optical recording medium.

A semiconductor laser device is usually used in the optical head. FIG. 5 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 the beam splinter 3 is incident on the photodetector 7.

That is, in this optical head 1, three optical components, the semiconductor laser 2, the beam splitter 3, and the photodetector 7, constitute the semiconductor laser device 8.

[Problem that the invention seeks to solve]

However, in such a semiconductor laser device 8, the three optical components are separated from each other, and when assembling the optical head 1, it is necessary to adjust the positions of these three optical components. Therefore, the semiconductor laser device W8 is large and expensive, and the optical head 1 is also expensive.

[Means for solving problems]

According to the present invention, a semiconductor laser device 21 includes a semiconductor laser 26 fixed to a substrate 24, and a semiconductor laser 26 fixed to a substrate 24.
A photodetector 32 is fixed to the substrate 24 so as to be inclined with respect to the output surface of the photodetector 32. The beams 4 emitted from the emission surface of the semiconductor laser 26 and reflected by the thin films 33 are used as irradiation beams, and the beams 4 that are incident on the thin films 33 are used as irradiation beams. The beam 4 passing through the photodetector 33 is detected by the photodetector 32.

[Effect]

In the semiconductor laser device 21 according to the present invention, irradiation of the beam 4 and detection of the incident beam 4 are performed by an integrated optical component.

Also, a photodetector 32 is connected to the emission surface of the semiconductor laser 21.
Since the photodetector 32 is inclined, the thin film 33 formed on the surface of the photodetector 32 has the function of a beam splitter.

Also, a photodetector 32 is connected to the emission surface of the semiconductor laser 21.
Since the photodetector 32 is tilted, the beam 4 reflected by the thin film 33 formed on the surface of the photodetector 32 does not directly return to the semiconductor laser 21 .

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 4.

As shown in FIG. 1, in the semiconductor laser device 21 of this embodiment, a substrate 24 is fixed on a stem 23 having leads 22, and a silicon substrate 25 is fixed on this substrate 24. A laser diode chip 26 is mounted on this silicon substrate 25, and a PIN diode 27, which is a photodetector for monitoring laser output, is formed.

Further, a silicon substrate 31 is fixed on the substrate 24 so as to be inclined with respect to the emission surface of the laser diode chip 26. A PIN diode 32, which is a photodetector for signal detection, is formed on this silicon substrate 31, and
A thin film 33 having a light transmittance and a reflectance of 50% is formed on the surface.

Note that in a medium in which the substrate 24 is a silicon substrate, an inclined surface with an inclination angle of 54.7° can be formed by etching, and if the substrate 24 is a metal substrate, an inclined surface with an inclination angle of 45° can be formed by processing. can be formed. Therefore, the silicon substrate 31 may be fixed to these inclined surfaces.

A cap 35 having a window glass 34 is mounted on the stem 23, and the above-mentioned optical system is hermetically sealed. Note that the laser diode chip 26 and the PIN diodes 27 and 32 are connected to each other by wires (not shown).

FIG. 2 shows an optical head using the semiconductor laser device 21 as described above. In this optical head 36, the beam 4 emitted from the laser diode chip 26 and reflected by the thin film 33 passes through the window glass 34 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 34.
The beam 4 transmitted through the thin film 33 is incident on the PIN diode 32.

Therefore, if a circuit as shown in FIG. 3 is used, the adder 41
, the reproduction signal from the subtracter 42 and the phase comparator 43, respectively.
A focus error signal and a tracking error signal can be obtained.

By the way, the beam that enters the PIN diode 32 is the beam 4 that has been modulated by the optical recording medium 6 and returned.
In addition, there is also a beam 4 that is emitted from the laser diode chip 26 and immediately passes through the thin film 33.

FIG. 4 shows the laser diode chip 26 to P
A method using a current-voltage converter is shown, which is an example of a method for electrically subtracting the signal amount of the beam 4 directly incident on the IN diode 32.

If the photocurrent due to direct incidence is 11 and the photocurrent due to the return beam is 2, then Il from the PIN diode 32
A photocurrent of +12 is obtained. For this purpose, the output voltage v2
is VZ = (It +1g) ・R+ +
V+ ' -=-(II +12--) ・
It becomes R+.

By the way, photocurrent! , is only the DC component.

Therefore, by setting Rz=V+/It, V
Z = Iz R+, and the influence of photocurrent ■ is removed. Note that the coil is for preventing the high frequency signal component of the photocurrent 1t from being shunted to the resistor R2 side.

In addition, in order to prevent direct or edge incidence from the laser diode chip 26 to the PIN diode 32, the thin film 33 should be a semi-transmissive type, not a polarizing type thin film, and as shown by the imaginary line in FIG. A 174 wavelength plate 44 may be arranged between the semiconductor laser device 21 and the objective lens 5.

In this way, the beam 4 emitted from the laser diode chip 26 as S-polarized light is totally reflected by the thin film 33, and 1
The light passes through the 74-wavelength plate 44 and becomes circularly polarized light. The returning beam 4 modulated by the optical recording medium 6 passes through the 174-wavelength plate 44, becomes p-polarized light, and completely passes through the thin film 33.

On the other hand, in the semiconductor laser device 21 of this embodiment, the PIN diode 27 is used as a back monitor for the laser diode switch knob 26. Therefore, the output of the laser diode chip 26 can be adjusted based on the output from the PIN diode 27.

Note that if the substrate 24 is a silicon substrate, this substrate 24
and the silicon substrate 25 can be integrated, and furthermore, the silicon substrate 31 can also be integrated.

[Effects 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.

Furthermore, since the thin film formed on the surface of the photodetector has the function of a beam splitter, the semiconductor laser device according to the present invention is small and low in cost.

Furthermore, since the beam emitted from the semiconductor laser does not directly return to the semiconductor laser, the semiconductor laser device according to the present invention generates less noise and is highly reliable.

[Brief explanation of drawings]

Figures 1 to 4 show one embodiment of the present invention.
The figure is a side sectional view, Figure 2 is a side view of an optical head to which one embodiment is applied, Figure 3 is a block diagram showing the circuit system of the optical head shown in Figure 2, and Figure 4 is a side view of an optical head to which one embodiment is applied. FIG. 2 is a circuit diagram of the current-voltage converter used. FIG. 5 is a side view of an optical head to which a conventional example of the present invention is applied. In addition, in the symbols used in the drawings, 4----------Beam 21-.・−・・−Substrate 26・・・−・
−1−−−・Laser diode chip 32−−−
−−−−−−・−・−・−PIN diode 33−
・−・−−−−−−−−−− Thin film.

Claims (1)

[Scope of Claims] A semiconductor laser fixed to a substrate; a photodetector fixed to the substrate so as to be inclined with respect to the emission surface of the semiconductor laser; and a photodetector formed on the surface of the photodetector. and a thin film that reflects a predetermined beam of the incident beam and transmits the remaining beam, and uses the beam emitted from the emission surface of the semiconductor laser and reflected by the thin film as the irradiation beam, A semiconductor laser device, wherein a beam incident on the thin film and transmitted through the thin film is detected by the photodetector.