JPH0821175B2 - Optical head device - Google Patents

Description

The present invention relates to an optical head device used as a light source for recording / reproducing information in an optical information recording / reproducing device for optically recording / reproducing information. .

[Conventional technology]

FIG. 2 is a schematic view of a conventional optical IC integrated optical head device disclosed in, for example, Japanese Patent Laid-Open No. 61-296540. In FIG. 2, (1) is the substrate, (2) is the buffer layer,
(3) is a dielectric thin film waveguide layer, (4) is a semiconductor laser,
Reference numeral (5) is a condensing grating coupler, which is formed on the dielectric thin film waveguide layer (3) and takes out light to the space outside the dielectric thin film waveguide layer (3), and on the information recording medium (6). A light condensing spot (7) is formed at one point, and reflected light from the information recording medium (6) is reflected by a dielectric thin film waveguide layer (3).
Perform the action of leading to. (8) is an information pit on the information recording medium (6), and (9) is a beam splitter, which are symmetrical with respect to the central optical axis in the direction in which the reflected light from the information recording medium (6) travels at a predetermined acute angle. It is divided into two and converged. (10) is a photodetector, which is formed on the substrate (1) so as to receive the light beam (11) divided into two by the beam splitter (9). Reference numeral (10a) is an electrode for taking out an electric signal from the photodetector (10) to the outside.

The optical head device shown in FIG. 2 is the main part (12) of the optical head device in the form of an optical IC, and means such as oxidation or vapor deposition on the substrate (1) of this main part (12). To form a dielectric thin film waveguide layer (3) by vapor deposition or sputtering, and then a condensing grating coupler (5) and a beam splitter (9) are formed on the dielectric thin film waveguide layer. (3) It is formed on another dielectric layer provided above by a photolithography or electron beam drawing method and a plasma etching method.

Next, the operation of the conventional optical head device based on the above configuration will be described. The luminous flux emitted from the semiconductor laser (4) is injected and guided into the dielectric thin film waveguide layer (3), and is extracted outside the dielectric thin film waveguide layer (3) by the condensing grating coupler (5). The light is collected as a light collecting spot (7) on the information recording medium (6). Information is recorded or reproduced by forming or detecting the information spot (8) by the light-condensing spot (7). The reflected light from the information recording medium (6) is guided through the dielectric thin film waveguide layer (3) through the condensing grating coupler (5) and the beam splitter (9), and is reflected by the photodetector (10). The light is received and converted into an electric signal. This electrical signal is the electrode (10a)
From the external electric circuit system (not shown), and a control signal for causing the information signal (8) on the information recording medium (6) to properly focus and track the reproduction signal and the focusing spot (7). To be detected.

[Problems to be Solved by the Invention]

Since the conventional optical head device is configured as described above, it has the following problems. This will be described with reference to FIG. FIG. 3 is a schematic diagram showing the problems in the conventional example, and the reference numerals (1) to (12) are the second.
It is the same as the one in the figure. Reference numeral (13) is a monitor photodetector arranged so as to receive the backward emission light (14) of the semiconductor laser (4), and the output signal of the monitor photodetector (13) is a semiconductor laser drive circuit (15). )It is connected to the. The semiconductor laser drive circuit (15) is a semiconductor laser (4)
Monitor photodetector (13) that received the rearward emission light (14)
It is determined whether the semiconductor laser (4) is emitting light with a predetermined light output based on the output signal of (1), and a drive current I of the semiconductor laser (4) is supplied so as to emit light with a predetermined light output.

Usually, the structure as described above is generally used to control the optical output of the semiconductor laser (4).
In addition to the main part (12) of the integrated optical head device, a monitor photodetector (13) is required, and the rearranged light (14) of the semiconductor laser (4) can be efficiently adjusted and arranged at a position where it can be received efficiently. However, it has not been able to fully utilize the merit of making an optical IC that can integrally form various optical elements.

The present invention has been made to solve the above problems, and in a main part of an optical head device having an optical IC, a monitor photodetector for detecting the optical output of a semiconductor laser which is a light source is provided. An object is to obtain an integrally formed optical head device.

[Means for solving the problem]

In the optical head device according to the present invention, a concave portion is provided in a part of a substrate including a dielectric thin film waveguide layer of a condensing grating coupler in a main portion, a semiconductor laser is accommodated and fixed in the concave portion, and a rear portion thereof is provided. And a photodetector for monitoring formed in the dielectric thin film waveguide layer, and an electric circuit for injecting a current for driving a semiconductor laser based on an output signal from the photodetector for monitoring. And

[Action]

The monitor photodetector according to the present invention can efficiently detect the backward emission light of the semiconductor laser that is the light source.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an optical head device in the form of an optical IC according to this embodiment. In the figure, reference numerals (1) to (12) and reference numerals (14) and (15) are the same as or correspond to those in FIGS. 2 and 3 of the conventional example, but in particular, a condensing grating coupler (5 ), Which is slightly larger than the shape (width and length) of the semiconductor laser (4) behind the position of the condensing point in the dielectric thin film waveguide layer (3), and behind the semiconductor laser (4). The semiconductor laser (4) is provided with a recess (16) having a depth such that the emitted light (14) can be efficiently injected and guided in the dielectric thin film waveguide layer (3).
The position is adjusted and fixed. On the substrate (1) in the direction of the backward emission light (14) of the semiconductor laser (4), a photodetector (17) for monitoring is built. Reference numeral (17a) is an electrode for taking out an electric signal from the photodetector for monitoring (17) to the outside, and is connected to the semiconductor laser drive circuit (15).

Next, the operation of this embodiment will be described. The light flux emitted from the semiconductor laser (4) is focused on the information recording medium surface (6) by the focusing grating coupler (5),
Further, the point that this reflected light flux is received and detected by the photodetector (10) is the same as in the conventional example. Semiconductor laser (4)
The rear emission light (14) is detected by the photodetector (17) for monitoring built into the substrate (1), and the semiconductor laser drive circuit (15) causes the semiconductor laser (4) to output a predetermined light output. It is determined whether or not it is emitting light. Then, the drive current I of the semiconductor laser (4) is supplied so as to emit light with a predetermined light output.

〔The invention's effect〕

As described above, in the optical head device according to the present invention, a photodetector for monitoring is formed in the dielectric thin film waveguide layer of the substrate that is made into an optical IC so as to efficiently receive the backward emission light from the semiconductor laser. In addition, the current is injected into the semiconductor laser based on the output signal from the photodetector for monitoring, so the optical output of the semiconductor laser can be detected and set to a predetermined value without the need for an external photodetector. There is an effect that an optical head that can be held and that various optical elements can be integrally formed is fully utilized, and an inexpensive optical head with high productivity can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an optical head device according to an embodiment of the present invention, and FIGS. 2 and 3 are perspective views showing a conventional optical head device. (1) ... substrate, (3) ... dielectric thin film waveguide layer,
(4) ... Semiconductor laser, (5) ... Condensing grating coupler, (9) ... Beam splitter, (10) ... Photodetector, (12) ... Main part of optical head, ( 14)……
Back-emitted light, (17) …… Monitor photodetector. In each drawing, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Koike 1st Baba Institute, Nagaokakyo City, Kyoto Prefecture Electronic Product Development Laboratory, Mitsubishi Electric Corporation (72) Inventor Keizo Kono 1st Baba Institute, Nagaokakyo Kyoto Prefecture Mitsubishi Electric (56) References JP-A-62-259241 (JP, A) JP-A-63-102053 (JP, A)

Claims (1)

[Claims] 1. A semiconductor having a surface on which a dielectric thin film waveguide layer is formed, and a semiconductor which is housed and fixed in a recess formed in a part of the surface of the substrate and injects laser light into the dielectric thin film waveguide layer. A laser, and a focusing grating coupler formed on the dielectric thin film waveguide layer in a group of unequal-spaced curves and converging the laser light to one point on the surface of the information recording medium outside the dielectric thin film waveguide layer. A beam splitter that deflects the reflected light from the information recording medium surface in a direction different from the direction of the semiconductor laser; and a photodetector that receives the reflected light deflected by the beam splitter and converts the reflected light into an electric signal, A monitor photodetector which is formed in the dielectric thin film waveguide layer at a position rearward of the semiconductor laser and receives rear emission light of the semiconductor laser and converts it into an electric signal; and a monitor photodetector. Optical head apparatus having an electrical circuit means for injecting a current for driving the semiconductor laser based on the force signal.