JPS609770Y2 - acousto-optic element - Google Patents

Description

[Detailed description of the invention] The present invention relates to an acousto-optic element that utilizes the acousto-optic effect (light diffraction phenomenon caused by ultrasonic waves), and its purpose is to
The object of the present invention is to provide an acousto-optic element that has an optimal antireflection film and provides the highest transmittance even when the wavelengths of light used are different.

First, a conventional example will be explained based on FIG.

1 is a high frequency power source ranging from several MHz to about IGHz, and 2 is an ultrasonic generator, which is composed of an electroacoustic transducer such as a single crystal of lithium niobate (LiNb03).

Reference numeral 3 denotes an electrode 4, which is an acousto-optic medium that allows light and ultrasonic waves to interact, and is made of glass or single crystal, and both sides of the electrode 4 are optically polished to be especially smooth to form light input/output surfaces 4a and 4b.

Reference numeral 5 denotes an ultrasonic absorber provided to prevent the generation of ultrasonic standing waves in the acousto-optic medium 4.

Note that this ultrasonic absorber 5 is not necessary in the case of an acousto-optic element that utilizes standing ultrasonic waves generated in the acousto-optic medium 4.

6a and 6b are antireflection films deposited on the light input/output surfaces 4a and 4b to a thickness t, and are made of magnesium fluoride, barium fluoride, or the like.

7 is a light beam.

In the above configuration, when the film thickness t of the antireflection films 6a, 6b is changed (t□~off), the wavelength (input) of light and the reflectance R of light at the light input/output surfaces 4a, 4b of the acousto-optic medium 4 The relationship between the two is shown in FIG. 4, and there is an optimum film thickness for each wavelength of light.

(λ1 for tl, λ2 for cherry blossoms, λ3 for t3).

As is clear from FIG. 4, for example, when j=t□, the reflectance for light of wavelength λ1 is low and the transmittance is good, but when light of other wavelengths is used, the reflectance increases.

In other words, at other wavelengths, the loss in the amount of light is large, the light utilization rate is poor, and the light reflected inward from the output surface (4a or 4b) of the acousto-optic medium 4 interferes, causing the amount of output light to decrease. This was not practical because it had negative effects such as instability.

Therefore, the present invention provides an acousto-optic device that solves these problems.

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

Components that are the same as those shown in FIG. 1 are designated by the same reference numerals and explanations are omitted.

Reference numerals 8 and 9 denote antireflection films deposited on the light input/output surfaces 4a and 4b of the acousto-optic medium 4, the outer surfaces of which are shaped like steps, and the respective portions 8a to 8c and 9a to 9C. Thickness is t
l, t2. It is now t3.

Forming in a stepped manner in this way means that the anti-reflection coatings 8, 9
This can be done by using a shutter or the like during vapor deposition and changing the exposed area over time.

In the above configuration, light beams of different wavelengths 71.7°,
73, each of the light beams 71 to 73 is coated with antireflection coatings 8 and 9 depending on the wavelength of the light beams 71 to 73.
What is necessary is just to project to each part 8a-8C99a-9c.

For example, in FIG. 2, if the wavelength of the light beam 71 is λ1, this light beam 71 may be projected onto 8a with a film thickness of tl, and if the wavelength of the light beam 7□ is λ2, then 8b, and the wavelength of the light beam 73 enters.

If so, it is sufficient to project it to 8C.

According to the above embodiment, the outer surfaces of the anti-reflection films 8 and 9 were formed in a step-like manner, but as shown in FIG.
It may be formed into

In such a configuration, the wavelengths λ1~ of the light beams 71~73
It is sufficient to select a portion with a thickness suitable for λ3 and project it.

The above-mentioned inclined surfaces 8d and 9d can be formed by continuously changing the exposed portions using a shutter or the like during vapor deposition of the antireflection films 8 and 9.

As described above, according to the acousto-optic device of the present invention, an anti-reflection film whose reflectance with respect to the wavelength of light changes depending on the film thickness is adhered to the light incident surface and the light exit surface of the acousto-optic medium with a non-uniform film thickness. In addition, since the thickness of the first antireflection film attached to the light incident surface and the second antireflection coating attached to the light exit surface are made to match at approximately symmetrical positions, the thickness of the light beam to be used is Even when the wavelengths are different, it is possible to obtain the optimum light beam position, and it is possible to prevent the negative effects caused by loss of light quantity and reflection, which are the problems of the conventional example mentioned at the beginning.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view showing a conventional example, Fig. 2 is an exploded perspective view showing an embodiment of the invention, Fig. 3 is a perspective view of main parts showing another embodiment of the invention, and Fig. 4. is a graph showing the characteristics of an antireflection film. 4... Acousto-optic medium, 4a, 4b...
Light input/output surface, 7□~73...Light beam, 8,9
...Anti-reflection film, 8a-8c, 9a-9C...
・・・Step-like part of anti-reflection film, 8d, 9d...
...Slope surface.

Claims (1)

[Claims for Utility Model Registration] ■ An anti-reflection film whose reflectance with respect to the wavelength of light changes depending on the film thickness is adhered to the light incident surface and the light exit surface of the acousto-optic medium with a non-uniform film thickness, and An acousto-optic element in which a first antireflection film attached to an incident surface and a second antireflection coating attached to the light exit surface have the same film thickness at substantially symmetrical positions. 2. The acousto-optic device according to claim 1 of the utility model registration, characterized in that the outer surface of the anti-reflection film is formed in a stepped shape. 3. The acousto-optic device according to claim 1, which is characterized in that the anti-reflection film is formed with slopes at appropriate locations on the outer surface thereof.