JPH053360A - Light stabilizer for laser - Google Patents

Abstract

PURPOSE:To attenuate laser light without generating heat and, at the same time, to highly stabilize the light intensity of the laser light by precisely, continuously, and variably adjusting the attenuating quantity. CONSTITUTION:A high-refractive index plate 4 is provided in front of the reflecting surface of a total-reflection prism 2 at a small interval. The small interval is precisely changed by means of a small displacement element 6. Because of the principle of this light stabilizer utilizing evanescent waves produced on the total reflection surface of the prism 2, the light intensity of the laser light is attenuated by leading part of the light energy of the laser light in a different direction. The attenuating quantity is fed back and controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser optical stabilizer for precisely adjusting and stabilizing 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. Further, if the output of the laser oscillator fluctuates, the intensity of the beam emitted from the attenuator also fluctuates, so that high stabilization cannot be expected.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is not to generate heat but to continuously and precisely attenuate the intensity of laser light to highly stabilize it. The present invention is to provide an optical stabilizer for a laser.

[0005]

SUMMARY OF THE INVENTION A laser optical stabilizer according to the present invention comprises a prism for totally reflecting a laser beam to change its course, and a high pitch disposed outside the reflecting surface of the prism with a minute gap. A refractive index plate, a minute displacement element that minutely changes the distance between the high refractive index plate and the prism surface, a light detection unit that detects the intensity of the outgoing beam reflected by the prism, and the detected light intensity. Feedback control means for driving the minute displacement element so as to make the deviation zero based on the deviation from the set value.

[0006]

The optical attenuator is composed of the prism, the optical refractive index plate and the minute displacement element. This optical attenuator applies the action of the evanescent wave associated with total internal 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.

In the laser optical stabilizer of the present invention, a feedback control system is combined with the optical attenuator, and the minute displacement element is automatically controlled so that the intensity of the emitted beam matches the set value. ..

[0012]

1 and 2 show the schematic construction of an optical stabilizer for a laser according to an embodiment of the present invention. First, the optical attenuator portion will be described in detail.

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 between the glass plate 5 and the prism 2 at the periphery of the joint surface.
There is a very small gap between the center of the prism 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 distance 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 size (size in the stacking direction of the piezoelectric plates) changes minutely depending on the applied voltage, and is used in combination with the drive circuit 8 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

Next, the feedback control system will be described. A part of the outgoing beam 3 from the prism 2 (optical attenuator) is branched by the beam splitter 9 and received by the optical sensor 10. A detection signal of a level corresponding to the intensity of the emitted beam 3 is output from the optical sensor 10, and is input to the controller 12 via the amplifier 11. The controller 12
The output of the optical sensor 10 is compared with the set value, and a control signal in the direction of making the deviation zero is given to the drive circuit 8. The drive circuit 8 applies a voltage having a magnitude corresponding to the control signal to the piezoelectric actuator 6. In this way, the optical attenuation amount is automatically controlled so that the intensity of the outgoing beam 3 matches the set value.

[0017]

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. By performing feedback control of this optical attenuation amount, it is possible to obtain a laser beam that is stabilized with extremely high precision.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical stabilizer for a laser according to an embodiment of the present invention.

FIG. 2 is a perspective view of an optical attenuator according to the embodiment.

[Explanation of symbols]

 1 incident beam 2 total reflection prism 3 outgoing beam 5 glass plate (high refractive index plate) 6 piezoelectric actuator (small displacement element) 8 drive circuit 9 beam splitter 10 optical sensor 11 controller

Front Page Continuation (72) Inventor Seio Kihara 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. (72) Inventor Akira Sasaki 836 Otani, Shizuoka City, Shizuoka Prefecture 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 (72) Invention Person 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. Based on the deviation between the detected light intensity and the set value, a minute displacement element that minutely changes the interval between the rate plate and the prism surface, a light detection unit that detects the intensity of the outgoing beam reflected by the prism. An optical stabilizer for a laser, comprising a feedback control means for driving the minute displacement element so that the deviation becomes zero.