JPS61296540A - Optical head device - Google Patents

Abstract

PURPOSE:To form an effective spot light on a disc while excluding aberration without scattering to an incident light by dividing a return light from a light collection grating coupler into two at a prescribed sharp angle by means of a beam splitter so as to send the result to a photodetector. CONSTITUTION:The titled device consists of a semiconductor laser 4 injecting a laser beam to a dielectric thin film conductive path layer 3 on the surface of a base 1, the light collection grating coupler 6 formed on the layer 3 as unequal interval curve groups and converging a laser light into one point light collection spot 14 on a dielectric thin film disc 8, photodetectors 10, 10 formed while being imbedded to the base 1, and the beam splitter 5 formed between the semiconductor laser 4 and the light collection grating coupler 6 and converging the light while dividing symmetrically into two at an angle of 30 deg. each with respect to the center optical axis in relation to the progressing direction of a reflected light from the disc 8 obtained by the coupler 6. Thus, the reflected light from the disc 8 converged by the beam splitter 5 is received by the photodetectors 10, 10 and converted into an electric signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc device for optically recording and reproducing information, and in particular to an optical disc device that accurately converges a spot on a disc used for reading and writing information. The present invention relates to an optical head device that can be used.

[Conventional technology]

FIG. 2 is a schematic diagram of a conventional optical head device implemented as an optical IC. In Figure 2, (1) is the substrate, (2) is the buffer layer, (3) is the dielectric thin film waveguide layer, (4) is the semiconductor laser, and (5) is the dielectric thin film waveguide layer (3). A beam splitter (8), which is an optical element formed on the top and separates incident light and reflected light, is formed on the dielectric thin film waveguide layer (3) similarly to the beam splitter (5), and splits the light into a dielectric layer. A condensing grating coupler that extracts light from the dielectric thin film waveguide layer (3) to an external space and focuses it on a single point, or guides the reflected light from this focal point to the dielectric thin film waveguide layer (3). , (12) are collimating lenses that convert the laser light injected into the dielectric thin film waveguide layer (3) by the semiconductor laser (4) into parallel light beams.

The optical head device shown in FIG. 2 is a main part (11) of an optical head device converted into an optical IC.
11) A buffer layer (2) is provided on the substrate (1) by means such as oxidation or vapor deposition, and a dielectric thin film waveguide layer (3) is further formed by vapor deposition or sputtering. Optical grating coupler (6), collimating lens (12), etc. are created on another dielectric layer provided on the dielectric thin film waveguide layer (3) by photolithography or electron beam drawing method and plasma etching method. do.

Next, the operation of the conventional optical head device based on the above configuration will be explained. The light emitted from the semiconductor laser (4) is collimated by the collimating lens (12), passes through the beam splitter (5), is focused by the condensing grating coupler (6), and is focused onto a spot (14) on the disk (not shown). ). The light reflected by this disk passes through the condensing grating coupler (6) again, is bent by 80 degrees with respect to the optical axis of the reflected light at the beam splitter (5), and enters the photodetector (10), where it is further transmitted to an electrical signal. can be changed to

[Problem that the invention seeks to solve]

Conventional optical head devices using optical ICs have a beam splitter that bends the reflected light by 90 degrees, so the incident light from the semiconductor laser to the condensing grating coupler is scattered and aberrations are increased. Therefore, there were problems such as the spot on the disk being spread out.

This invention was made to solve the above-mentioned problems, and its purpose is to provide an optical head device that eliminates scattering of incident light and eliminates aberrations to produce an effective spot light on a disk. It is something to do.

[Means for solving problems]

The optical head device according to the present invention divides the reflected light from the information recording surface obtained by the condensing grating coupler into two parts symmetrically at predetermined acute angles about the central optical axis with respect to the traveling direction of the reflected light. Equipped with a beam splitter to converge
This is an a-configuration in which the reflected light from the information recording surface, which is focused by the beam splitter, is received by a photodetector and converted into an electrical signal.

[Effect]

The optical head device according to the present invention uses a beam splitter to symmetrically divide the return light from the condensing grating coupler (reflected light from the information recording surface) into two parts at a predetermined acute angle and send it to the photodetector. Scattering of laser light to the condensing grating coupler and aberration can be eliminated.

Furthermore, the returned light can be divided into two parts each having a narrow angle of 30 degrees or less with respect to the central optical axis and sent to the photodetector, thereby effectively preventing scattering and aberration of the returned light.

Furthermore, the beam splitter has convergence properties +1 &,
(effect of a weak convex lens), the laser light is converged closer to the condensing grating coupler than the light emission source point, and the photodetector can be embedded in the substrate.

〔Example〕

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

FIG. 1 shows an overall schematic diagram of this embodiment, and in the same figure, the optical head device according to this embodiment emits laser light to a dielectric thin film waveguide layer (3) formed on the surface of a substrate (1). The injected semiconductor laser (4) and the dielectric thin Jli waveguide R (3) are formed in a group of irregularly spaced curves, and the laser beam is directed to the information recording surface outside the dielectric thin film waveguide layer (3). A condensing grating coupler (6) is embedded in the substrate (1) to converge the light at one point on the disk (8) (14), and Grating coupler (6) that condenses the luminous flux (7) of
A photodetector (10) that receives light and converts it into an electrical signal.
.

(10) and the traveling direction of the reflected light from the disk (8) formed between the semiconductor laser (4) and the condensing grating coupler (8) and obtained by the condensing grating coupler (6). A beam splitter that divides the central optical axis into two parts symmetrically at an angle of 30 degrees and converges them.
5), and a photodetector (10) that detects the reflected light from the disk (8) focused by the beam splitter (5);
(10) It is configured to receive light and convert it into an electrical signal.

Next, the operation of the optical head device according to this embodiment based on the above configuration will be explained. First, laser light is injected from the semiconductor laser (4) into the dielectric thin film waveguide layer (3).
The laser light transmitted through the dielectric thin film waveguide layer (3) is connected to the dielectric thin film waveguide N by the condensing grating coupler (6).
(3) Focused spot (1) on the disk (8) outside
4).

Here, the laser light emitted by the semiconductor laser (4) passes through the beam splitter (5) and is sent to the condensing grating coupler (8).
5) is formed with a symmetrical narrow inclination angle (30 degrees or less) into two parts, so that scattering and aberrations when the laser light passes through can be eliminated as much as possible.

Furthermore, after reading the signal pit (9) of the disk (8) with the laser beam focused on the focused spot (14), the light beam (7) reflected from the disk (8) is transferred to the focusing grating coupler. (6) leads it again into the dielectric thin film waveguide layer (3). The guided laser beam is split into two sides by a beam splitter (5) symmetrically at an angle of 30 degrees with respect to the central optical axis in the traveling direction of the laser beam, and is converted into a convergent beam. This two-split convergent laser beam (15),
(15) is sent to a photodetector (10) while preventing scattering and aberration, and is efficiently converted into an electrical signal by the photodetector (10).

The beam splitter (5) limits the return light from the condensing grating coupler (6) to a small angle of 30 degrees or less between the optical axis and the splitting direction, and splits the light into two in symmetrical directions around the optical axis. The beam splitter connects the semiconductor laser (4) to the condensing grating coupler (6).
Since it can be configured to reduce defects that scatter incident light and increase aberrations, it is possible to reduce the distortion on the disk to a small size.

In addition, by providing this beam splitter with weak convergence (for example, a convex lens effect), the focal point for the returned light can be moved from the vicinity of the mounting surface of the semiconductor laser (4) of the optical IC substrate (1) to the condensing grating coupler (6). ), and the embedded photodetector (10), (io)
This has the effect of facilitating the construction of the .

〔Effect of the invention〕

As described above, the optical head device according to the present invention allows the reflected light from the information recording surface obtained by the condensing grating to be symmetrically arranged at predetermined acute angles to the central optical axis with respect to the direction in which the reflected light travels. The beam splitter is equipped with a beam splitter that splits the beam into two and converges, and the light reflected from the information recording surface that is focused by the beam splitter is received by a photodetector and converted into an electrical signal. The return light from the condensing grating coupler (reflected light from the information recording surface) is split into two at a predetermined acute angle (for example, 30 degrees or less) and sent to the photodetector, and the light from the semiconductor laser to the condensing grating coupler is This makes it possible to eliminate scattering and aberrations of the laser beam, and has the effect of narrowing down the spot of the laser beam on the disk to create an effective spot light.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram of an optical head device according to an embodiment of the present invention, and FIG. 2 is an overall schematic diagram of a conventional device. (1) is the substrate, (2) is the buffer layer, (3) is the dielectric thin film waveguide layer, (4) is the semiconductor laser, (5) is the beam splitter, (
6) is a focusing grating coupler, (7) is a light beam, (8) is a disk, (9) is a signal bit, (10) is a photodetector, (14) is a focused spot, (15) is a focused laser beam . Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Diagram 1 procedural amendment (1 issue) May 4, 1986

Claims (4)

[Claims] (1) A semiconductor laser that injects laser light into a dielectric thin film waveguide layer formed on the surface of a substrate; An optical head device comprising a condensing grating coupler that focuses light on a single point on an information recording surface outside the thin film waveguide layer, and a photodetector that receives reflected light from the information recording surface and converts it into an electrical signal. , a beam splitter formed between the semiconductor laser and the condensing grating coupler, which splits the reflected light from the information recording surface obtained by the condensing grating coupler into two parts symmetrically at predetermined acute angles with respect to the central optical axis; What is claimed is: 1. An optical head device comprising: a photodetector that receives reflected light from an information recording surface obtained by the beam splitter and converts it into an electrical signal. (2) The beam splitter is configured to split the laser beam sent out from the condensing grating coupler into two at an angle of 30 degrees or less with respect to the central optical axis of the laser beam. The optical head device according to item 1. (3) The beam splitter is configured to converge the laser beam sent out from the condensing grating coupler and form a convergence point at a point closer to the condensing grating coupler than the laser beam emission source point, which is the position of the semiconductor laser. An optical head device according to claim 1 or 2, characterized in that: (4) The optical head device according to any one of claims 1 to 3, wherein the photodetector is embedded in a substrate.