JPS63229644A - Optical pickup - Google Patents

Abstract

PURPOSE:To obtain a small-sized and light-weight optical pickup having a simple structure by providing two grating couplers coupled to light beams different by 90 deg. in polarization direction from each other. CONSTITUTION:The optical pickup consists of a first grating coupler 5 which polarizes the TE or TM mode among a semiconductor laser beam propagated in an optical waveguide and radiates it to the space, a second grating coupler 6 which is so constituted that the polarized light different by 90 deg. in polarization direction from this polarized light is coupled to this coupler 6 and is propagated in an optical waveguide 3, and a photodetector 8 which detects the propagated light. That is, the difference of effective refractive index between the TE mode and the TM mode in the waveguide 3 is used to separate and take out light beams having the same polarization direction by a difference between exit angles from grating couplers 5 and 6. Thus, the small-sized and light-weight optical pickup for magneto-optical disk having the mass-productivity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical pickup for reading information stored magneto-optically on a magneto-optical disk or the like.

2. Description of the Related Art In recent years, magneto-optical disk devices have been attracting attention as large-capacity storage devices for text files, image files, and the like.

A conventional optical pickup used in this magneto-optical disk device will be explained below. FIG. 2 shows an example of the configuration of a conventional optical pickup.

The light emitted from the semiconductor laser 14 is made into parallel light by a lens 15, passes through a polarizer 18, the polarization directions are aligned, passes through a beam splitter 17, and is focused by an objective lens 18 and irradiated onto a magneto-optical disk. magneto-optical disk 1
The polarization direction of the light reflected by the magneto-optical disk 19 is rotated according to the information recorded on the magneto-optical disk 19.

This reflected light becomes parallel light by the objective lens 18, is reflected by the beam sinter 17, and enters the analyzer 20. The intensity of the light transmitted through the analyzer 20 changes in accordance with the rotation angle of the polarization direction described above. Therefore, by receiving this light with the photodiode 21, information on the magneto-optical disk can be read.

Problems to be Solved by the Invention However, the conventional configuration described above uses a large number of optical components, which complicates the assembly process and makes mass production difficult. Another problem was that the shape became large.

The present invention solves the above-mentioned conventional problems, and aims to provide an optical pickup for magneto-optical disks that is small and lightweight and can be mass-produced.

Means for Solving the Problems The optical pickup of the present invention includes a semiconductor laser and an optical integrated circuit optically coupled to the semiconductor laser,
The optical integrated circuit includes an optical waveguide through which the light emitted from the semiconductor laser is divided into TE and 7M modes and propagated, and the light of either mode is polarized onto the surface of a substrate on which information is magneto-optically recorded. Among the light reflected from the substrate surface, which has the magneto-optic effect and whose polarization direction is rotated according to the recorded information, the grating coupler has a light-concentrating grating coupler that irradiates light with a polarization direction perpendicular to the irradiation light. It includes a grating coupler that selectively introduces light into the optical waveguide, and a light receiving element that converts the light introduced into the optical waveguide and propagated into an electrical signal.

Furthermore, the optical pickup of the present invention can be used in an optical integrated circuit to pick up the TE of semiconductor laser light propagating through an optical waveguide.
Or a first grating coupler that polarizes one of the 7M modes and radiates it into space, and a second grating coupler that is configured so that this light and polarized light whose polarization direction is different by 90' are combined and propagated through an optical waveguide. It consists of a grating coupler and a light receiving element that detects propagating light.

Function The pickup of the present invention uses a grating coupler that emits a polarized component in one direction of the light emitted from a semiconductor laser to the outside, and the pickup uses a grating coupler that emits the polarized component in one direction of the light emitted from the semiconductor laser to the outside. is used to separate and extract light with the same polarization direction due to the difference in the output angle from the grating coupler.

Furthermore, by utilizing the difference in effective refractive index between the TE mode and the 7M mode, it is possible to guide only the vertical component of the polarization direction rotated by the Kerr effect out of the reflected light from the magneto-optical disk to the waveguide. It becomes possible.

Embodiment Hereinafter, an optical pickup according to an embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 shows the configuration of an optical pickup in an embodiment of the present invention. In FIG. 1, 1 is a silicon substrate, 2 is a buffer layer, and 3 is a waveguide layer, which constitute a slab optical waveguide. Reference numeral 4 denotes a semiconductor laser which is optically coupled to the aforementioned slab optical waveguide by direct coupling at the end face. 6,6
is a condensing grating coupler, which is formed on the above-mentioned slab waveguide, and the grooves 7 optically separate the two. 6 is a TE mode, and 6 is a 7M mode, each of which is designed to couple with externally emitted light or externally incident light.

Reference numeral 8 denotes a light receiving element, which is formed on the silicon substrate 1 so as to be optically coupled to the slab waveguide.

The operation of the optical pickup configured as described above will be explained below.

First, the emitted light 10 from the semiconductor laser 4 is introduced into the waveguide layer 3 by direct coupling at the end face, and then enters the condensing grating coupler 6 . The incident light 1o is emitted upward from the waveguide layer by the condensing grating coupler 5.

Since the refractive index of the waveguide layer is different between TE mode and 7M mode,
The emission angle also differs. Therefore, the light emitted from the condensing grating coupler 6 is separated into light 11 polarized in a direction parallel to the waveguide layer and light whose polarization direction differs from this by 90°. Outgoing light 11 from the condensing grating coupler 6 is reflected by the magneto-optical disk 9 and enters the condensing grating coupler 6 as light 12. At this time, the polarization direction of the light 12 is rotated according to the information recorded on the magneto-optical disk 9 due to the Kerr effect. Due to the difference in the refractive index of the light 12 between the TE mode and the TM mode, only the component whose polarization direction differs by 90' from the polarization direction of the light 11 is introduced into the waveguide layer as the light 13. This light 13 enters the light receiving element 8 and is converted into an electrical signal.

As mentioned above, two
By using two grating couplers, it is possible to construct an optical pickup for a magneto-optical disk with a simple structure.

Effects of the Invention As described above, according to the present invention, by providing two grating couplers that respectively couple lights with polarization directions different by 90', it is possible to realize a small and lightweight optical pickup with a simple structure.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an optical pickup according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a conventional optical pickup. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... Buffer layer, 3... Waveguide layer, 4... Semiconductor laser, 6, 6... ... Concentrating grating coupler, 8 ... Light receiving element, 9 ... Magneto-optical disk. Name of agent: Patent attorney Toshi Nakao and one other person t4-
--Chi exclusive Resi 1to ＼ 1cares

Claims (1)

[Claims] The optical integrated circuit includes a semiconductor laser and an optical integrated circuit optically coupled to the semiconductor laser, and the optical integrated circuit includes an optical waveguide through which light emitted from the semiconductor laser is divided into TE and TM modes and propagated; A light-converging grating coupler that polarizes and irradiates light in one mode onto the surface of a substrate on which information is recorded magneto-optically, and has the above-mentioned magneto-optic effect, causing rotation of the polarization direction depending on the recorded information. a grating coupler that selectively introduces light whose polarization direction is perpendicular to the irradiated light from among the light reflected from the surface of the substrate into the optical waveguide; and a light receiver that converts the light introduced into the optical waveguide and propagated into an electrical signal. An optical pickup comprising an element.