Diffraction optical device and optical apparatus using the same

Details Diffraction optical device and optical apparatus using the same Diffraction optical device and optical apparatus using the same

2001-12-12

2003-06-03

Epps, Georgia (Department: 2873)

Optical: systems and elements

Optical modulator

Light wave directional modulation

C359S312000

Reexamination Certificate

active

06574035

ABSTRACT:

The present application claims priority to Japanese Patent Application No. 2000-378502 filed Dec. 13, 2000, the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus using an acoustooptic device.
2. Description of the Related Art
Various kinds of acoustooptic devices made of lithium niobate LiNbO
3
or the like have been proposed. For example, U.S. Pat. No. 5,657,152 discloses an acoustooptic device in which on an LiNbO
3
substrate, an optical waveguide layer having a higher light refractive index than the LiNbO
3
substrate is formed and a Rayleigh wave, which is a kind of surface acoustic wave, is excited on the optical waveguide layer to thereby deflect light. U.S. Pat. No. 5,138,482 discloses a light modulator in which a light beam is divided into a plurality of beams by use of an optical waveguide made of a material capable of propagating surface elastic waves and the difference in modulation timing among a plurality of light beams is eliminated.
The above-described conventional optical devices use an interdigital transducer (hereinafter, abbreviated as IDT) to deflect light. The basic structure of the IDT is shown in FIG.
1
. In the IDT
101
, a comb-shaped electrode
102
a
having a plurality of linear electrode fingers
103
a
and a comb-shaped electrode
102
b
having a plurality of linear electrode fingers
103
b
are opposed to each other so that the electrode fingers
103
a
and
103
b
are interdigitated. An oscillator
104
applies a voltage of a predetermined frequency to the comb-shaped electrodes
102
a
and
102
b.
FIG. 2
shows the IDT
101
formed on an optical waveguide layer
105
. When the voltage of the predetermined frequency is applied to the IDT
101
by the oscillator
104
, a surface acoustic wave
106
is generated on the optical waveguide layer
105
. When a light beam is incident on the optical waveguide layer
105
, the surface acoustic wave
106
diffracts a light beam
107
as schematically shown in FIG.
3
. The angle of diffraction depends on the frequency and the elastic modulus of the optical waveguide layer
105
.
However, the conventional optical devices are capable of deflecting light only within the same plane.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a diffraction optical device having a light condensing property like that of a lens by using an acoustooptic device.
Another object of the present invention is to provide an optical apparatus in which the focal length is easily adjusted.
These and other objects are attained by a diffraction optical device comprising an optical waveguide made of an acoustooptic material, an interdigital transducer provided on the optical waveguide and in which a plurality of arc-shaped electrode fingers are interdigitated so that the interdigital transducer is substantially circular in shape as a whole, and an oscillator device for applying a voltage of a predetermined frequency to the interdigital transducer.
The substantially circular shape includes a circle, an annular shape, and a circle and an annular shape a part of which is cut away.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings.


REFERENCES:
patent: 3582838 (1971-06-01), Devries
patent: 5138482 (1992-08-01), Hatori et al.
patent: 5400788 (1995-03-01), Dias et al.
patent: 5657152 (1997-08-01), Kadota
patent: 5953027 (1999-09-01), Suwabe et al.
patent: 5-107480 (1993-04-01), None
patent: 10-319446 (1998-12-01), None

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