JPH052141A - Optical attenuator for laser - Google Patents

Abstract

PURPOSE:To suppress heat generation and to adapt the optical attenuator to a large-output laser beam without any problem by attenuating the light intensity of a main optical path by guiding a part of light energy in another direction. CONSTITUTION:An incident beam 1 is reflected by a total reflecting prism 2 to become a projection beam 3. A glass plate 5 as a high-refractive-index plate 4 is joined with the surface of the reflecting surface 4 of the prism 2 and an extremely thin spacer is sandwiched in the peripheral part of the joined surface between the glass plate 5 and prism 2 to leave a gap between the center part of the glass plate 5 and the surface of the prism 2. A lamination type piezoelectric actuator 6 is used as a fine displacement element which precisely control the fine interval between the glass plate 5 and prism 2. The fine interval between the glass plate 5 and prism 2 can be adjusted by controlling the voltage applied to the piezoelectric element 6 to finely and continuously vary the intensity (light attenuation quantity) of the projection beam 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser optical attenuator for precisely adjusting the intensity of laser light from a laser oscillator.

[0002]

2. Description of the Related Art Although various studies have been made on the stabilization of the output of a laser oscillator and the stabilization of the wavelength, it is currently difficult to arbitrarily change the output while keeping the wavelength constant. Therefore, in order to arbitrarily adjust the intensity of the laser light having a constant wavelength, the laser beam from the laser oscillator must be appropriately attenuated by the optical attenuator.

[0003]

The conventional optical attenuator uses a filter made of a glass plate whose density value (light transmittance) is adjusted in multiple stages. Since the energy of the absorbed light changes into heat in the filter, the density value of the filter will change due to heat generation when passing a laser beam with a slightly larger output, and the filter will be damaged if the heat generation is large.
Also, the filter cannot continuously change and adjust the laser light intensity.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to generate a laser beam which can continuously and finely adjust the intensity of the laser beam without causing heat generation. To provide an attenuator.

[0005]

An optical attenuator for a laser according to the present invention comprises a prism for totally reflecting a laser beam to change its course, and a high-powered reflector disposed outside the reflecting surface of the prism with a minute gap. It is provided with a refractive index plate and a minute displacement element for minutely changing the distance between the high refractive index plate and the prism surface.

[0006]

The laser optical attenuator of the present invention applies the action of the evanescent wave associated with the total reflection. As is well known, the total reflection is 100% of the light reflected by the boundary surface when the light travels from the transparent first medium having a high refractive index (the prism) to the transparent second medium having a low refractive index (air). It is a phenomenon.

When light is totally reflected, it does not mean that the light does not enter the second medium at all, but it travels in the second medium parallel to the boundary surface, and its amplitude is proportional to the distance from the boundary surface. There are light waves that decay exponentially and rapidly. This is called an evanescent wave.

Therefore, a third medium having a high refractive index (the high refractive index plate) is placed in the second medium, and is opposed to the first medium with a very thin layer of the second medium (the minute gap) interposed therebetween. .. Then, the energy of light can be transmitted to the third medium via the evanescent wave. This phenomenon is explained as a kind of tunnel effect, and is used in prism couplers for dielectric optical waveguides and certain semi-transparent mirrors.

That is, 100% of the light is not reflected at the boundary surface, and part of the light travels toward the third medium. Therefore, the intensity of the light reflected by the boundary surface is correspondingly reduced. Then, the amount of energy of light transmitted to the third medium via the evanescent wave changes depending on the distance between the first medium and the third medium.

The optical attenuator according to the present invention operates on the above principle. That is, when the laser beam from the laser oscillator is reflected by the prism, part of the energy of the laser beam escapes from the reflecting surface to the high refractive index plate side, is reflected by the prism, and is an outgoing beam that is guided to the utilization system. Intensity is lower than that of total reflection. The amount of energy of light that escapes to the high refractive index plate side changes by changing the minute gap between the plate and the prism. Therefore, if the distance is controlled by the minute displacement element, the intensity of the emitted beam, that is, the attenuation amount can be continuously and arbitrarily adjusted.

[0011]

1 and 2 show the schematic construction of an optical attenuator for a laser according to an embodiment of the present invention. The incident beam 1 is reflected by the total reflection prism 2 to become an outgoing beam 3. The glass plate 5 as the high refractive index plate is bonded to the surface of the reflecting surface 4 of the prism 2. A very thin spacer is sandwiched in the peripheral portion of the joint surface between the glass plate 5 and the prism 2, and a very small gap is maintained between the central portion of the glass plate 5 and the surface of the prism 2.

A laminated type piezoelectric actuator 6 is used as a minute displacement element for precisely controlling a minute gap between the glass plate 5 and the prism 2. As shown in the figure, a frame 7 that covers the glass plate 5 is integrally fixed to the prism 2, and the frame 7 and the glass plate 5 are connected by a columnar piezoelectric actuator 6. The piezoelectric actuator 6 is an element whose dimensions (dimensions in the stacking direction of the piezoelectric plates) change minutely depending on the applied voltage, and is used in combination with a drive circuit that controls the applied voltage.

By controlling the voltage applied to the piezoelectric actuator 6, the minute gap between the glass plate 5 and the prism 2 is adjusted, whereby the intensity (light attenuation amount) of the outgoing beam 3 is finely and continuously changed. Can be made

[0014]

The laser optical stabilizer of the present invention attenuates the light intensity of the main optical path by letting a part of the light energy escape to another direction by the principle of utilizing the above-mentioned evanescent wave generated on the total reflection surface. Therefore, unlike a filter that absorbs and attenuates light energy, almost no heat is generated and a high-power laser beam can be handled without any problem. Further, by electrically controlling the minute displacement element, the light attenuation amount can be precisely and continuously variably adjusted.

[Brief description of drawings]

FIG. 1 is a plan view of an optical attenuator for a laser according to an embodiment of the present invention.

FIG. 2 is a perspective view of the optical attenuator.

[Explanation of symbols]

 1 incident beam 2 total reflection prism 3 exit beam 5 glass plate (high refractive index plate) 6 piezoelectric actuator (small displacement element) 7 frame

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masao Kihara 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. (72) Inventor Akira Sasaki 836 Otani, Shizuoka-shi, Shizuoka Shizuoka University (72 Inventor Naoyuki Aoyama 836 Otani, Shizuoka City, Shizuoka Prefecture Shizuoka University (72) Inventor Kenji Murakami 836 Otani Shizuoka City, Shizuoka Prefecture Shizuoka University (72) Inventor Kenji Ishikawa 836 Otani Shizuoka City, Shizuoka Prefecture Shizuoka University ( 72) Inventor Takashi Nomura 836 Otani, Shizuoka City, Shizuoka Prefecture Shizuoka University

Claims (1)

Claim: What is claimed is: 1. A prism for totally reflecting a laser beam to change its path, a high refractive index plate arranged at a minute interval outside the reflecting surface of the prism, and this high refractive index. An optical attenuator for a laser provided with a minute displacement element that minutely changes the distance between the index plate and the prism surface.