JPS62196880A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To reduce the cost of a semiconductor laser by both emitting a beam and detecting an incident beam by an integral optical component to readily regulate an optical path. CONSTITUTION:A photodetector 13 is formed on a substrate 12, and a prism 21 having a translucent reflecting surface 21a and at least one of reflecting surface 21b, 21c is fixed to the photodetector 13. A beam 16 emitted from a semiconductor laser 11 fixed on the semiconductor substrate 12 and reflected by the surface 21a is used as an emitting beam. The beam 16 incident to the surface 21a, passed through the surface 21a and further reflected on the surface 21b, 21c is detected by the photodetector 13.

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]

In the semiconductor laser device as described above, the present invention integrates a semiconductor laser, a photodetector, and a beam splinter,
Moreover, the beam splitter is provided with a function of generating astigmatism, and the beam is reflected one or more times in the beam splitter before detection, thereby making the apparatus compact and low in cost.

[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, and the semiconductor laser device includes optical components such as a semiconductor laser, a beam splitter, an astigmatism generating element, and a photodetector.

However, in conventional semiconductor laser devices, since the above-mentioned optical components are separate components, many man-hours are required to adjust the optical path, making it difficult to reduce costs.

Further, since the semiconductor laser device requires many optical components as described above, there is a limit to the miniaturization and cost reduction of the optical head.

Therefore, a semiconductor laser device 10 as shown in FIG. 2 has been considered. This semiconductor laser device IO has a semiconductor laser 11 fixed to a semiconductor substrate 12 such as a Si substrate, a photodetector 13 formed on the semiconductor substrate 12, and a prism 14 mounted on the photodetector 13 using an adhesive. The beam splinter function and the function of astigmatism generation are performed on the prism 14 by making the beam 16 in a converged state from the optical recording medium 15 obliquely enter the prism 14.
It was designed to have both functions.

[Problem that the invention seeks to solve]

However, even in such a semiconductor laser device 10, it is necessary to insert a spacer 17 between the semiconductor laser 11 and the semiconductor substrate 12.

If this spacer 17 were not present, the beam 16 from the optical recording medium 15 would enter the prism 14 at a position close to the semiconductor substrate 12, and the optical path length of the beam 16 would be shortened after the astigmatism occurs in the prism 14. . As a result, the astigmatism difference of the beam 16 becomes smaller, and the spot size of the beam 16 on the best image plane, that is, on the photodetector 13, also becomes smaller.

When the astigmatism difference becomes smaller, the pull-in range of focus servo becomes narrower, making it impossible to perform focus servo stably.

Furthermore, when the spot size becomes smaller, a large portion of the spot enters the dead zone of about 5 μm width that divides the photodetector 13 into four, making it impossible to perform focus servo with high sensitivity. It is necessary to align the two with high precision, and a high precision assembly process is required, making it difficult to reduce costs.

Therefore, the spacer 17 is necessary, but if the spacer 17 is used, the spacer 17 will be attached to the semiconductor substrate 12.
It is necessary to align the semiconductor laser 11 with respect to the spacer 17. For this reason, not only is it difficult to miniaturize the semiconductor laser device 10, but also in this case, a highly accurate assembly process is required, which also makes it difficult to reduce costs.

Further, in order to make the beam 16 from the optical recording medium 15 enter the prism 14 at a position far from the semiconductor substrate 12 by using the spacer 17, it is necessary to use a large prism 14. Therefore, this also makes it difficult to downsize the semiconductor laser device IO.

[Means for solving problems]

A semiconductor laser device 20 according to the present invention includes a semiconductor substrate 12
a photodetector 13 formed on the photodetector 13; a prism 21 fixed on the photodetector 13 and having a transflective surface 21a and at least one reflective surface 21b, 21c; and the semiconductor substrate 12. Semiconductor laser 1 fixed to
A beam 16 emitted from the semiconductor laser 11 and reflected by the semi-transparent reflecting surface 21a is used as an irradiation beam, and a beam 16 emitted from the semiconductor laser 11 is used as an irradiation beam, and
The photodetector 13 detects the beam 16 that is incident on the transmissive reflective surface 21a, transmitted through the semi-transparent reflective surface 21a, and further reflected by the reflective surfaces 21b and 21c.

[Effect]

In the semiconductor laser device 20 according to the present invention, irradiation with the beam 16 and detection of the incident beam 16 are performed by an integrated optical component.

Furthermore, if the beam 16 obliquely incident on the transflective surface 21a of the prism 21 is in a convergent state, astigmatism will occur in the beam 16 as it passes through the transflective surface 21a. It has both the function of a beam splitter and the function of generating astigmatism.

Moreover, the beam 16 that has entered the prism 21 is reflected by one or more reflecting surfaces 21b and 21C, and then the photodetector 1
3, the optical path length of the beam 16 within the prism 21 can be increased even if the beam 16 is incident on the prism 21 at a position close to the semiconductor substrate 12. Therefore, if applied to a device that performs focus servo using the astigmatism method, focus servo can be performed stably by increasing the astigmatism difference and widening the pull-in range. By increasing the spot size above, focus servo can be performed with high sensitivity and the positional accuracy of the device can be relaxed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the semiconductor laser device 2 of this embodiment
0, a semiconductor laser 11 is directly fixed to a semiconductor substrate 12 by tin solder or the like, and a prism 2 having a trapezoidal cross section is attached.
The structure may be substantially the same as that of the previously described semiconductor laser device 10 shown in FIG. 2, except that the semiconductor laser device 1 is fixed to the semiconductor substrate 12.

However, in this prism 21, the surface 21a facing the semiconductor laser 11 is a semi-transmissive reflective surface as in the case of the prism 14, but the surface 21b facing the semiconductor substrate 12 is the surface 21a facing the photodetector 13. Parts other than the vicinity of and surface 21
21C, which faces b, both serve as reflective surfaces.

In the semiconductor laser device 20 of this embodiment, the surface 2
The beam 16 entering the prism 21 from 1a is directed to the surface 2
The light is reflected by the reflective surface portion of 1b and the surface 21c, and then detected by the photodetector 13.

Note that in this embodiment, the semiconductor substrate 12 is the semiconductor laser 11.
It serves as a heat sink for the

〔Effect of the invention〕

Since the semiconductor laser device according to the present invention is an integrated optical component, the optical path can be easily adjusted and the cost is low.

Furthermore, since the prism has both the function of a beam splitter and the function of generating astigmatism, when applied to a device that utilizes astigmatism, the device can be made smaller and lower in cost.

Moreover, when applied to a device that performs focus servo using the astigmatism method, even if the incident beam enters the prism at a position close to the semiconductor substrate, focus servo can be performed stably and with high sensitivity, and the device can be Since the positional accuracy can be relaxed, there is no need to insert a spacer between the semiconductor laser and the semiconductor substrate, and the device is small and low cost.

[Brief explanation of drawings]

FIG. 1 is a side view showing one embodiment of the present invention, and FIG. 2 is a side view showing a conventional example. In addition, in the symbols used in the drawings, 11-・・・−・−−1−−・−・−・・−・−Semiconductor laser 12−・−・−・−・−・・・−・− Semiconductor substrate 13 - - - - - Photodetector 16 - - - m = - - - - - - - Beam 20 - -・・・−・・−−−−−−−・・・・−
Semiconductor laser device 21-----1...--------
111... Prisms 21a, 21b, 21c -
・It is a ----- surface.

Claims (1)

[Scope of Claims] A photodetector formed on a semiconductor substrate; a prism fixed on the photodetector and having a transflective surface and at least one reflective surface; and the semiconductor substrate. a semiconductor laser fixed to the semiconductor laser, and a beam emitted from the semiconductor laser and reflected by the semi-transparent reflective surface is used as an irradiation beam, and a beam incident on the semi-transparent reflective surface and reflected by the semi-transparent reflective surface is used as an irradiation beam. A semiconductor laser device in which a beam transmitted through the surface and further reflected by the reflective surface is detected by the photodetector.