JPS6299927A - Optical pickup - Google Patents

Abstract

PURPOSE:To attain miniaturization and high speed accessing by forming a thin film optical guide path mode of a calcogenide on an acoustooptic crystal and applying an ultrasonic surface elastic wave to the acoustooptic crystal so as to apply optical deflection. CONSTITUTION:The waveguide path 3 made of a calcogenide glass is formed on the AO crystal delivering a surface acoustic ultrasonic wave by the sputtering or vapor deposition. The laser light from a semiconductor layer 4 is a linear collimated luminous flux by a flat lens 6 formed in the calcogenide glass guide path 5 and subject to optical deflection by an ultrasonic wave from an optical deflector 7. The light subjected to the light deflection is irradiated in air through a grating coupler 8 formed on the calcogenide guide path and stopped on an optical disc 9. The light reflected in the optical disc 9 passes again through the grating coupler 7 and the 0-th order light reaches the photodetector 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pickup for a small optical disk using a guiding waveguide.

[Background of the invention]

An optical disk pickup that combines an acousto-optic (AO) crystal and an optical waveguide can be miniaturized and have high-speed access because mechanical driving parts can be removed from the optical pickup. This type of pickup is proposed, for example, in Japanese Patent Application No. 58-236165.

However, the optical waveguide using the commonly used AO crystal is L
iNb0a with Ti diffused therein is used.

At this time, the refractive index changes very easily, and it is difficult to form patterns with different refractive indexes within the waveguide.

In such a situation, the waveguide only propagates light, and the prism coupler C is required to introduce light into the waveguide.
For example, Proceedings of the 30th Society of Applied Physics, p176 (1983
) 4a-J-4], photoresist gratings [e.g.
On Gradient-Index Optical
Imaging Systems 4th Topical M
eating on Gradient-index o
ptical imaging systems”tp
p170-173 (1983) Fe ], etc. It is necessary to use another means. Also, a lens inside the waveguide.

It is difficult to embed optical elements such as beam splitters.

[Purpose of the invention]

The present invention uses A S z S as an optical waveguide constituent material.
Lenses by using chalcogenide glass such as a.

The purpose of this invention is to form a grating or the like in a waveguide to solve the above problems.

[Summary of the invention]

The outline of the present invention is shown in FIG. 1. An electrode 2 for exciting surface ultrasound is attached to an AO crystal 1 that transmits surface elastic ultrasound. A signal is applied to the electrode 2 from a high frequency generating power source to generate surface ultrasonic waves. On the other hand, a waveguide 3 made of chalcogenide glass such as A S z S a is formed on the crystal by sputtering, vapor deposition, etc. 6 Light propagates in the chalcogenide waveguide 3 . Ultrasound is A
○It propagates on the surface of the crystal, but even if a thin film-shaped guide waveguide made of chalcogenide glass with a thickness of about 1 μm is attached to the crystal, the wavelength is smaller than the wavelength of ultrasonic waves, which is 10 μm to 100 μm, so it leaks through the chalcogenide glass and propagates. To go. An optical pickup based on such a configuration is provided. 10
o is an incident beam, and 101 is an outgoing beam.

[Embodiments of the invention]

FIG. 2 shows an embodiment of the optical pickup according to the present invention.

The laser beam emitted from the semiconductor laser 4 is converted into a one-dimensional parallel beam by a plane lens 6 formed in a chalcogenide glass waveguide 5, and is optically deflected by an ultrasonic wave from an optical deflector 7. This optically polarized light exits into the air through a grating coupler 8 formed in a chalcogenide waveguide and is focused onto an optical disk 9. Note that in FIG. 7, the optical pickup is shown in an exaggerated manner. The light reflected by the optical disk 9 passes through the grating coupler 7 again and reaches 0.
The next light reaches the light detection base 10. In this way, a chalcogenide glass optical waveguide with a lens and a lens with a chalcogenide glass optical waveguide can be used to create an optical pickup that has the function of a beam spiriter.

The following method is used to create the grating coupler and beam splitter. When chalcogenide glass is exposed to light or electron beams, its refractive index changes significantly.
To make a lens like 6 in the figure, a lens is formed by irradiating chalcogenide glass with an optical mask or by irradiating it with a single beam to create a state in which the refractive index changes. Further, a grating coupler or a beam splitter is a grating in which thin lines are carved on an optical waveguide, and the grating can also be formed by irradiating light or electron beams through a mask. At this time, the crystal 1 is about 2 mm thick, and the chalcogenide glass is a thin film about 0.5 to 1 μm thick. The size of lenses, prisms, etc. is 2 to 4 meters and 8 degrees in diameter.

In FIG. 3, light emitted from a laser 11 is introduced into a waveguide through a grating coupler made of chalcogenide glass. The light that has passed through the deflector 13 passes through the parallel grating coupler 15 and exits from the waveguide into the air.

The laser beam exiting from the parallel grating coupler becomes a parallel beam of light, which is focused onto the optical disk by a lens 16 located outside. In this way, the tracking deflector can be replaced with a conventional galver mirror or the like without a mechanical drive unit.

FIG. 4 shows an example in which a beam splitter 20 for guiding light to a detector 19 in a waveguide is formed of chalcogenide glass. Laser light emitted from a semiconductor laser 21 directly enters the waveguide and passes through a waveguide lens 22. After passing through, it passes through an ultrasonic deflector 23. Thereafter, the beam 11 passes through a splitter 20 formed of chalcogenide glass by EB or optical lithography, exits the optical pickup by a grating coupler 25, and is focused at a position 24 corresponding to the surface of the disk. The light reflected from the disk passes through a beam splitter 2o through a reverse optical path and heads toward a photodetector 9.

〔Effect of the invention〕

As described above, according to the present invention, chalcogenide glass is used as an optical waveguide, lenses, gratings, and beam splitters are formed therein, and an AO crystal such as LiNb0a that propagates surface ultrasound is used for the optical deflector part. in,
Optical pickups with various functions can be constructed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIGS. 2 to 4 are diagrams each showing other embodiments of the present invention.

Claims (1)

[Claims] 1. In an optical pickup for condensing a minute spot on an optical disk to form pits and to read information from the pits, an acoustic device whose refractive index changes by applying ultrasonic waves. An optical pickup characterized in that a thin film optical waveguide made of chalcogenide is formed on an optical crystal, and light is deflected by applying an ultrasonic surface acoustic wave to the acousto-optic crystal. 2. The optical pickup according to claim 1, wherein the thin film optical waveguide is provided with a refractive index distribution to provide lens imaging, grating, or beam splitter functions.