JPS6218520A - Ultrasonic optical modulator - Google Patents

Abstract

PURPOSE:To obtain a non-dispersive ultrasonic optical modulator which has excellent characteristics of the phases of ultrasonic waves and can be easily manufactured at an inexpensive cost by installing on a main boundary surface an ultrasonic wave irregularly reflecting area reflecting irregularly the spurious of the ultrasonic wave radiated from a transducer. CONSTITUTION:The titled modulator is equipped with ultrasonic wave irregularly reflecting areas 14 and 15 on the main boundary surfaces 12 and 13. The spurious S of a longitudinal wave 8 made incident on the main boundary surfaces 12 and 13 from an input transducer 10 at an angle almost parallel in said surfaces is subjected to the mode conversion from a longitudinal wave to a transversal one, or from transversal to longitudinal, and is irregularly reflected as a transversal or longitudinal wave. Accordingly, the spurious wave vanishes in the ultrasonic wave irregularly reflecting areas 14 and 15 and is removed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an ultrasonic optical modulator, and particularly to an ultrasonic optical modulator having good characteristics and
The present invention relates to an ultrasonic optical modulator that is easy to manufacture and inexpensive.

[Technical Background of the Invention] As shown in FIGS. 6(a) and (b), when a laser beam 42 is incident on a sound wave 41 (velocity V, wavelength included) traveling in a transparent medium 40, diffracted light 43 is generated. can get. The intensity of the diffracted laser beam 43 changes depending on the intensity of the sound wave 410. Therefore, by changing the applied amplitude of the sound wave 41, the intensity of the diffracted laser beam 43 can be modulated. The optical configuration of such an ultrasonic optical modulator is shown in FIG. In the same figure, a high frequency signal is applied by a drive source 46 to an electrode 45 of a transducer 44 disposed at one end of an ultrasonic optical transparent medium 40 to cause the ultrasonic waves to proceed to the ultrasonic optical medium 40 . A laser beam 41 is made incident on the ultrasonic wave emitted to the medium to obtain a diffracted beam 43. In addition, 47.
49 is Avachia, 48.50 is a person, output lens, 51
is an ultrasonic absorbing material provided at the other end of the ultrasonic optical medium 40. By the way, one of the major factors for obtaining a high-performance ultrasonic optical modulator is to move the ultrasonic optical medium into the ultrasonic optical medium as shown in FIG. 6(a).
As shown in (b), strong ultrasonic waves with the same phase propagate.

For this reason, conventionally, as shown in FIG. 8, of the ultrasonic waves 41, which are generally longitudinal waves, emitted from the transducer 44 into the ultrasonic optical medium 40, only the phase C and d portions of the ultrasonic waves are emitted into the ultrasonic optical medium 40. Sound waves a, b, c, d, and e are transmitted to the ultrasonic optical medium 40 without causing photoacoustic interaction and causing acoustic interaction and obliquely traveling as side lobes.
The waves are reflected by the slope 52 of the ultrasonic optical medium 40 and absorbed by the absorbing material 51 provided on the other surface 53 of the ultrasonic optical medium 40, thereby preventing generation of return sound waves.

[Problems with the background art] Such an ultrasonic optical modulator uses phase-aligned sound waves, c
, d requires the ultrasonic optical medium to be thick, and the cost is high because it is manufactured one by one.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional difficulties, and it is an object of the present invention to provide an ultrasonic optical modulator that has good characteristics, is easy to manufacture, and is inexpensive.

[Summary of the Invention] In order to achieve the above object, the ultrasonic optical modulator of the present invention uses an ultrasonic wave emitted to an ultrasonic optical medium by a transducer placed on one surface of the medium. In an ultrasonic optical modulator that obtains diffracted light by making the ultrasonic optical medium incident on at least a part of a main boundary surface perpendicular to the one surface of the ultrasonic optical medium, a spurious wave of the ultrasonic wave emitted from the transducer is transmitted to at least a part of the main boundary surface that is perpendicular to the one surface of the ultrasonic optical medium. This is provided with an ultrasonic diffused reflection area that causes diffused reflection on the surface.

[Embodiments of the invention] Preferred embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the ultrasonic optical modulator of the present invention has the following features:
A transducer 10 is arranged on one surface 2 of an ultrasonic optical medium 1 made of, for example, a single crystal of lead molybstate, tellurium oxide, etc. or heavy flint glass. transducer 10
is made of, for example, lithium niobate single crystal. The optical configuration of the ultrasonic optical modulator that makes the light 41 incident on the ultrasonic wave radiated to the medium 1 by the transducer 10 to obtain the diffracted light 43 is the same as that shown in FIG. is omitted.

As shown in FIG. 3, the longitudinal waves 8 emitted from the transducer 10 cover at least a portion of the main boundary surface 12, 13 perpendicular to one surface 2 of the ultrasonic optical medium 1, almost the entire surface in the illustrated example. Ultrasonic diffused reflection region 14 that diffusely reflects the spurious ultrasonic waves S at the main boundary surface! 5. The roughness of the surface of the ultrasonic diffuse reflection region 14.15 is λ/20 to λ/5 of the wavelength λ of the propagating ultrasonic wave. When the surface roughness is finer than λ/20 of the wavelength of the transmitted 1114 sound wave, λ/
If it is coarser than 5, the desired diffused reflection will not occur, so any of these is not preferable.

The thickness of the transducer 10 is the same width (indicated by 1) as the thickness of the ultrasonic optical medium 1, and the main boundary surface]2.1
It is orthogonal to 3 (indicated by ?R).

However, the electrodes of the transducer 10 (not shown) need not have the same width as the thickness of the ultrasound optical medium 1. Moreover, the thickness of the ultrasonic optical medium 1 is 50 mm of the wavelength λ of the propagating ultrasonic wave.
λ to lOλ. The light beam is usually about 1 mm thick, and the thickness of the ultrasonic optical medium is about 5 mm thick compared to the propagating ultrasonic wave.
If it is thicker than 0, material is wasted, and if it is thinner than 10λ, the light beam cannot pass through it.

According to the ultrasonic optical modulator configured in this way, the transducer 1 disposed on one surface 2 of the ultrasonic optical medium 1
The longitudinal wave 7 emitted from the transducer 10 to the surface at 90° propagates in the ultrasonic optical medium 1 (the wave emitted from the transducer 10 to the surface at 90° is a transverse wave instead of the longitudinal wave 70). ). This longitudinal wave 7 may be absorbed by an ultrasonic absorbing material 16 provided on the other surface of the ultrasonic optical medium 1.

As described above, in the ultrasonic optical modulator according to the present invention, since the transducer 10 has the same width (to) as the thickness of the ultrasonic optical medium 1, the transducer 10 substantially has the function of not emitting mote waves other than the 0 mode. This facilitates the construction of a non-dispersive mode ultrasonic light modulator.

However, as shown in FIG. 3, waves 8 almost parallel to the main boundary surfaces 12 and 13 are generated, resulting in spurious waves S. That is,
The ultrasonic spurious S of the longitudinal wave 8 emitted from the transducer 10 is subjected to longitudinal wave-to-transverse wave conversion or longitudinal wave-to-longitudinal wave conversion at the main boundary surface 12.13, and is diffusely reflected as a transverse wave or a longitudinal wave. The diffused reflection portion is typically indicated by 11.

This situation will be explained with reference to FIG.

When a longitudinal wave 8 is incident on the interface 5 between the solid medium I and the fluid medium 2 at an angle α, a transverse wave 9 appears in addition to the longitudinal wave 8a as reflected waves. The reflection angle α of longitudinal waves is equal to the incidence angle α, but the reflection angle β of transverse waves is different. The relationship between the reflection angles in these reflections is Sinα/Sinβ=Cpl/Csl. Note that Cpl is the propagation velocity of longitudinal waves in medium I, C
sl is the propagation velocity of the transverse wave in medium I.

The ratio of the amplitude of the artificial longitudinal wave 8 and the reflected longitudinal wave 8a depends on the angle of incidence α using the Poisson's ratio of the medium I as a parameter.

In the present invention, the ultrasonic diffused reflection area 14.15 is provided on at least a part of the main boundary surface 12.13, and in the illustrated example, on almost the entire surface, so that the ultrasonic wave is radiated from the human quadrangle juicer 10 parallel to the main boundary surface 12.13. As explained in Fig. 5, the spurious wave of the longitudinal wave 8 which is incident at an angle close to , is at least partially converted into a mode between a longitudinal wave and a transverse wave, or is converted into a longitudinal wave and a longitudinal wave, and is diffusely reflected as a transverse wave or a longitudinal wave. Therefore, the spurious waves disappear and are removed in this ultrasonic diffuse reflection region 14,15. Furthermore, if an ultrasonic absorbing material such as epoxy resin is bonded onto the ultrasonic diffuse reflection region 14.15 of the main interface 12.13, this spurious wave will be absorbed by the main interface 12.1.
3, which improves the spurious wave removal effect.

Note that the transducer 10 connects two parallel main interfaces 1
2.13, the rectilinear longitudinal wave 7 emitted from the transducer 10 travels straight between the main boundary surfaces 12 and 13.

In manufacturing such an ultrasonic optical modulator, as shown in FIG. 5, a block 40 of an ultrasonic optical medium l having a rectangular shape with pre-designed dimensions is prepared. A tin electrode 41 is attached to one surface 2 by vapor deposition. A transducer strip 43 is placed above it. This is cut by a slicing machine to obtain each unit 1-45 provided with the transducer 10. The main boundary surface of each unit 45 is roughened to form ultrasonic diffuse reflection regions 14 and 15 (FIG. 3).

According to this manufacturing technique, a block of ultrasonic optical medium formed into a polygon with a pre-designed shape and size is cut into units with a transducer strip provided thereon, so that each of the obtained units Therefore, the ultrasonic waves will not be irregular, and a high-quality ultrasonic optical modulator can be obtained. Furthermore, since the transducer is cut to have the same width as the thickness of the ultrasonic optical medium, it is easy to construct a non-dispersive mode ultrasonic optical modulator.

[Effects of the Invention] As is clear from the above embodiments, according to the present invention, light is incident on an ultrasonic wave emitted by a transducer placed on one surface of an ultrasonic optical medium to the medium, and diffracted. When obtaining light, an ultrasonic diffuse reflection area is provided on at least a part of the main boundary surface perpendicular to one surface of the ultrasonic optical medium to diffusely reflect the spurious waves of the ultrasound emitted from the transducer at the main boundary surface. , a non-dispersive ultrasonic optical modulator can be obtained that has good characteristics due to the uniform phase of ultrasonic waves, is easy to manufacture, and is inexpensive.

Also, the thickness of the ultrasonic optical medium can be reduced, which saves material. Furthermore, an ultrasonic light modulator that is easy to manufacture and of high quality is provided.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an ultrasonic optical medium applied to an ultrasonic optical modulator according to the present invention, and FIG. 2 is a side view of the same ultrasonic optical medium.
Fig. 3 is an enlarged side view of the ultrasonic optical medium, Fig. 4 is an explanatory diagram of the operation of the ultrasonic optical medium, Fig. 5 is an explanatory diagram of the manufacturing of the ultrasonic optical medium, and Fig. 6 is an An explanatory diagram showing the principle of an ultrasound optical modulator, FIG. 7 is an optical configuration diagram of a general ultrasound optical modulator, and FIG. 8 is a side view of an ultrasound optical medium in a conventional ultrasound optical modulator. 1... Ultrasonic optical medium 2... One surface 7... Ultrasonic wave (longitudinal wave) S... Spurious 10... Transducer 12.13... Main boundary surface 14.15... Ultrasonic diffused reflection area 43...Diffracted light agent Patent attorney Moritani-Yuu Figure 6

Claims (1)

[Scope of Claims] 1. An ultrasonic optical modulator that obtains diffracted light by making light incident on an ultrasonic wave emitted to an ultrasonic optical medium by a transducer placed on one surface of the medium; Ultrasonic waves, characterized in that an ultrasonic diffused reflection area is provided on at least a part of the main boundary surface perpendicular to the one surface of the optical medium to diffusely reflect the spurious waves of the ultrasonic waves emitted from the transducer on the main boundary surface. light modulator. 2. The ultrasonic optical modulator according to claim 1, wherein the transducer has the same width as the thickness of the ultrasonic optical medium and is orthogonal to the main boundary surface. 3. The thickness of the ultrasonic optical medium is 5 times the wavelength λ of the propagating ultrasonic wave.
The ultrasonic light modulator according to claim 1, wherein the wavelength is 0λ to 10λ. 4. The ultrasonic optical modulator according to claim 1, wherein the surface roughness of the ultrasonic diffuse reflection region is λ/20 to λ/5 of the wavelength λ of the propagating ultrasonic wave.