JPS6025915B2 - Ion laser oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas laser oscillator, and particularly to an ion laser oscillator including a wavelength selection element.

Among gas lasers, the ion laser oscillator provides the largest oscillation output in the visible range, and due to its high brightness, it is used as a light source for treatment of the fundus of the eye, a light source for Raman spectrometers, a light source for holography, etc.

The ion laser has a plurality of adjacent oscillation lines, and for purposes such as fundus treatment that simply utilizes energy, these oscillation lines may exist simultaneously. However, as light sources for Raman spectrometers and holography require monochromaticity of the oscillation line, a prism is inserted inside an optical resonator consisting of a pair of mirrors to select one of the many possible oscillation spectra. It resonates only with one oscillation line,
It has been attempted to obtain monochromatic laser output. However, with an ion laser, a current of several magnitudes is passed through the laser tube,
Since several kilowatts of power is input, the amount of heat generated by the Laser tube is extremely large, and the heat that cannot be removed even by water cooling causes thermal changes in the mirror holding mechanism, impairs the facing nature of the mirror, and lowers the laser output.

In addition, if a prism is installed inside the optical resonator to resonate only the one wavelength of interest from among the many possible oscillation spectra produced by the laser soot, single-wavelength oscillation can be performed. This thermal deformation of the prism holding mechanism slightly rotates the prism, causing a change in the optical path and causing a fluctuation in laser output. Furthermore, the biggest problem concerns the temperature characteristics of the refractive index of the prism material. That is, the optical path changes when passing through the prism due to a temperature change in the refractive index of the prism, which in turn causes a phenomenon similar to the output fluctuation due to a change in the optical axis. In this way, a laser oscillator in which a prism is placed inside an optical resonator has a large number of fluctuation factors compared to a normal laser oscillator, and this poses a major problem in terms of the reliability of the laser oscillator. Therefore, an object of the present invention is to eliminate fluctuations in laser output caused by the presence of a prism in a laser oscillator using an optical resonator including a prism, and to provide a stable single-wavelength oscillation ion laser device. .

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of a conventional ion laser oscillator in which a prism is inserted inside a resonator to perform single wavelength oscillation.

In Fig. 1, 1 is an ion laser tube, 24 output mirrors,
3 is its support, 4 is a reference plate used to correct the inclination of the mirror support 3 by adjusting the tuning screw 5, 6 is a prism for wavelength selection, 7 is its support, and 8 is the support 7. Components installed in the optical resonator include a total reflection mirror 9, its support 10, and a reference plate 11 for correcting the inclination of the mirror support 10 by adjusting the tuning screw 12. The two reference plates 4 and 11 and the component 8 have a coefficient of thermal expansion of 4. The mutual positional relationship of the reference plates 4 and 11, which are assembled into a tower shape together with a rod-shaped material 13 such as quartz, is determined by the thermal expansion coefficient. It is designed not to undergo any changes.

The entrance surface of the prism 6 is arranged to form a Prewster angle with respect to the optical axis. Even if an optical axis as shown by the dashed-dotted line in the figure is created at a certain temperature, if there is thermal deformation in 7, the optical axis will change as shown by the arrow, for example when rotation A is given to the prism. It will be done. This rotation A is caused by heat generation in the laser tube, for example (not shown in the figure).
It is assumed that 7 and 8 are thermally deformed because the upper part of the oscillator has a high temperature and the lower part has a low temperature.

For this reason, the optical path after passing through the prism changes due to the heat generated by the laser tube or changes in the environmental temperature, leading to a situation where the laser output changes. However, the rotation shown as rotation B occurs in the support body 1 of the total reflection mirror 9 for the same reason, so if the amounts of these two rotations A and B are equal, even if there is a change in the optical path. The orthogonality of the optical axis to the total reflection mirror 9 is not disrupted, and no change occurs in the laser output.
However, such a thing cannot generally be expected from the structure of the prism support 7 and the total reflection mirror support 10, and changes in output due to changes in the optical path are unavoidable due to either rotation A or B. . Moreover, as mentioned above, the change in the optical axis due to the change in the refractive index of the prism is the biggest factor in the fluctuation in output. Considering the characteristics of general optical materials, where the refractive index decreases as the temperature rises, the change in the optical axis caused by this temperature rise means that rotations A and B are in the same direction, making it difficult for changes in the optical path to lead to changes in output. This is a direction that completely independently impairs orthogonality between the total reflection mirror and the optical axis, and has a large impact on the stability of the laser output. In order to overcome this drawback, the present invention uses materials with different expansion coefficients to support the optical system, compensate for output fluctuation factors caused by temperature changes, and obtain stable oscillation output.

Next, an embodiment of the present invention will be described using FIG. 2.

In Fig. 2, 1 is an ion laser tube, 2 is an output mirror,
3 is its support, 4 is a reference plate used to adjust the appearance of the mirror support 3 by adjusting the tuning screw 5, 6 is a prism for wavelength selection, 7 is its support, and 9 is total reflection. mirror,
20 is a structure that accommodates a prism support as well as a support for the total reflection mirror; 11 is a reference plate used to correct the inclination of the structure 20 by adjusting the adjusting screw 12;
The reference plates 4 and 11 are integrated by a rod-shaped material 13 having a small expansion coefficient such as quartz or crystallized glass, but the structure 20 is made of a screw-shaped member having a different hot air expansion coefficient. It is held on a plate 27 via 25 and 26, and 2
8 is a fixing nut. In FIG. 2, member 25,
26 is the main element of the present invention, and as shown in FIG. 2, the prism and total reflection mirror, which were conventionally arranged in two separate locations in FIG. 1, are integrated using the structure 20. This is also the second element claimed by the present invention in that a large practical effect can be obtained for downsizing the laser oscillator.

It will be described below that the present invention can compensate for optical path fluctuations caused by fluctuations in the refractive index of the prism, which is the largest output fluctuation factor.

For convenience, the rotation amounts shown as rotation A and rotation B in FIG. 1 are treated as being equal. FIG. 3 is a diagram showing the principle of the optical path temperature compensation mechanism for adjusting the structure 20 in FIG.
In both figures, 6 is a wavelength selection prism, and 9 is a total reflection mirror. In both figures, the structure 201 is fixed to 6 and 9.
There is no difference in the relative positional relationship between the two. When the optical axis is optimally adjusted at the temperature shown in Figure a, the optical path 30 enters the prism at an angle Q to the incident surface, the Y total reflection mirror 9 and the optical axis are orthogonal, and the reflected light is Follow the light path. When the temperature of the prism increases due to changes in the surrounding temperature, the optical path changes to 31
As a result, the optical axis is no longer orthogonal to the total internal reflection mirror 9, and the positive feedback necessary for laser oscillation is lost, resulting in a decrease in laser output. However, if the horizontal structure 20 undergoes the rotation shown as C in Figure 3a in response to this temperature rise, then the light will enter the prism at an angle of 8 (8<Q) as shown in Figure 3b. Even though the refractive index of the emitted light is decreased, it remains orthogonal to the total reflection mirror 9, so that no change occurs in the laser output. In order to cause the rotation C described in connection with FIG. 3, it is a matter of course that the screw-shaped capital 25 is made of a material with a small expansion coefficient, and the screw-shaped capital 26 is made of a material with a large expansion coefficient. Furthermore, the amount of temperature compensation can be varied by changing the effective lengths of 25 and 26, but if 25 and 26 are screwed and the position of the fixing nut 28 is moved appropriately as shown in Figure 2, it is possible to The optimal temperature compensation amount can be found for each set by the chain strategy method. In the present invention, even if the prism and the total reflection mirror are integrated, only the structure 20 is held by members having different expansion coefficients, so that rotation of the structure 20 as the length of each member changes due to temperature changes. This is the reason why the temperature change in the laser output can be compensated for by using motion, and the wavelength selector can be made smaller and the output can be highly stabilized.

The only drawback of integrating the prism and mirror according to the present invention is that there is no compensation for fluctuations in laser output due to fluctuations in the optical path caused by rotations A and B that occur when the temperature changes as shown in Figure 1. This means that it is possible. However, as mentioned at the beginning, rotations A and B are in the same direction, and the output fluctuation due to the difference can be minimized by considering it at the time of design. This can be ignored when compared to the reliability improvement due to the reduction in parts produced by integration. According to an experimental example, a 50% change in laser output due to a temperature change of 10 qo of soil was reduced to 10% by this compensation effect. According to the present invention, the device can be downsized and the laser output can be stabilized, and the practical performance of a wavelength selective ion laser using a prism can be greatly improved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional wavelength-selective ion laser;
The figure is a sectional view of a wavelength-selective ion laser showing an embodiment of the present invention, and Figures 3a and 3b illustrate the principle of the invention. Figure 1 is an ion laser tube, 2 is an output mirror, and 3 is an output mirror support. ,
4 is a reference plate, 5 is a tuning screw 6 is a prism, 7 is a prism support, 8 is a part that holds the prism support, 9 is a total reflection mirror, 10 is a total reflection mirror support, 11 is a reference plate,
12 is a tuning screw, 13 is a rod, 20 is a structure for integrating a mirror and a prism, 25 and 26 are threaded members for temperature compensation, 27 is a support for the structure 20, 28 is a nut,
Lines 30, 31, and 32 indicate optical paths. Many diagrams, many Z diagrams, many 3 diagrams

Claims (1)

[Claims] 1. In an ion laser oscillator including an ion laser tube, a pair of mirrors arranged on both sides of the tube, and a wavelength selection prism arranged on the optical axis and near the one mirror,
One mirror and the prism are attached to one structure, and at least one support member attaching the structure to an angle adjustment mechanism that adjusts the angle of the structure is made of materials having different coefficients of thermal expansion. An ion laser oscillator characterized by: