JPS6037630B2 - Waveguide carbon dioxide laser oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waveguide C02 laser oscillator, and its object is to significantly increase the output (while keeping the overall length of the laser device the same as that of the prior art).

Carbon dioxide laser (hereinafter referred to as C02 laser) has a similar classification.

・d=constant ・・・・・・・【1}ls・d
= constant... ...'21 (P./
V)・tsubo=constant...'3' holds true. Here g. is the small signal gain, ls is the saturation parameter,
P. is the laser output, V is the gain section volume, and d is the laser tube diameter. G from this. and ls is inversely proportional to the pipe, output/
It can be seen that the volume ratio is inversely proportional to the square of the tube. The conventional C02 waveguide laser is as shown in Figure 1.
is a waveguide discharge tube, 12 is a waveguide, 13 is an output coupling mirror, 1
Reference numeral 4 is a total reflection mirror, and the diameter of the laser tube, that is, the diameter of the waveguide 12, is selected to be about d 1 willow ◇, and the output/volume ratio is 1 OW/cc, 2, compared to 0.5 W/cc of a normal diffusion-cooled laser. It also has the characteristic of being loud. However, since a small-diameter tube is used, the gain section volume V itself is small, and the output per unit length of the discharge tube is 10 W/W compared to the conventional laser's 50 W/W, which is a drawback. Therefore, conventional waveguide C02 lasers are only used for communications where high output is not required, and are not used as an energy source, although they have the potential to be made into small lasers. It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to increase the output of a waveguide C02 laser.

In the waveguide laser of the present invention, the laser medium gas is confined between two adjacent cooled parallel plates, and the cross section of the waveguide is rectangular. The cooling effect, which is an advantage of waveform lasers, is maintained and a high output volume ratio is achieved.

Furthermore, in the present invention, the horizontal side length of the rectangular waveguide cross section is made sufficiently longer than the vertical side length, for example, the horizontal side length/vertical side length (d) is about 100...■ The active area is increased by selecting the active area.

This numerical value of 10 tones may be considered to be an upper limit value limited by the difficulty level of discharge. At this time, the cooling effect is almost similar to that of a conventional waveguide laser, so the equations [1}~■ hold as they are, and the output/volume ratio is close to the value of a normal waveguide laser, while the gain volume is {4} Approximately 10 tones from the formula
Therefore, the output will be about 10 tones. FIG. 2 shows the configuration of a C02 waveguide laser according to the present invention.

In the figure, 21 is an insulator made of Pyrex, quartz, beryllia, etc., and is cooled by a method not shown in the figure. Of course, it can also be air cooled. Reference numeral 22 denotes a hollow discharge region provided in this insulator, and the length of the vertical side is selected to be about 1 rib, and the length of the horizontal side is selected to be about 50 to 100 legs.

This discharge region 22 is a known technique. A lateral discharge is performed by a large number of electrode groups 25 and 26, and a uniform glow discharge is obtained. A uniform glow area can also be obtained by performing electrodeless high-frequency discharge.
23 is a full mirror mirror, and 24 is an output coupling mirror, and these mirrors have a radius of curvature Rv in the vertical direction and a radius of curvature R in the horizontal direction.
It must be an aspherical mirror with h. The reason for this is that the laser resonator of the present invention is a kind of composite resonator that is a waveguide resonator in the vertical direction and a fabric bellows resonator in the horizontal direction, and both resonators are required for stable operation. This is because each has a different curvature. Vertical curvature R
In order to operate the waveguide laser resonator stably, the value of v may be selected so as to satisfy the following relationship: Rv=Z/Z (5) b: magazine... field.

This is not unambiguous, so in reality, given Rv, R
Place a reflector close to V) and change Z to adjust the oscillation output to Tsukadai. Here, Z is the position between the end of the waveguide and the reflecting mirror, d is the length of the vertical side of the waveguide, and ^ is the wavelength of 10.6 degrees. On the other hand, for the lateral curvature RH, if the reflector spacing is 1, an arbitrary value of RH<RH may be selected as a region in which the Fabry Bellows resonator operates stably. Incidentally, the output beam from the oscillator of the present invention is an irregular beam with different divergence angles due to vertical and lateral diffraction, and the patterns in the near field and far field have a relationship in which the vertical and horizontal ratios are reversed.

(If the oscillator of the present invention is applied to applications such as heat treatment where a laser beam uniformly scans a wide surface of a workpiece, please leave it as is)
However, for general applications, it is necessary to convert the output beam coming out of the output coupling mirror into a circular cross-section beam using an aspherical optical system, as shown in FIG. 3a shows the case using an aspherical lens, and 6 shows the case using an aspherical reflecting mirror. 31 is an output coupling mirror, which corresponds to 23 in FIG.

Note that the discharge tube is not shown. 32 is an aspheric optical system, 33
34 is the near field pattern of the laser beam in the output coupling mirror, 34 is the beam that is being expanded by diffraction up to the optical system, and 35 is the emitted beam having a substantially circular cross section due to the optical system.

The principle of FIG. 3 is as follows. Since the diffraction divergence angle is inversely proportional to the beam diameter, the near-field pattern and the far-field pattern have exactly opposite vertical and horizontal ratios, and there is a point where the vertical and horizontal beam diameters become equal after traveling a certain distance. do. Assuming that the distance between this point and the output coupling mirror is L, the aspherical optical system may be positioned at this point so that there is no lens effect in the lateral direction and it has just the focal length L in the vertical direction. In other words, in the horizontal direction, the divergence angle is negligible and the beam travels as a nearly parallel beam even after passing through the optical system, while in the vertical direction, the diffraction and expansion after exiting from the output mirror is significant, but the beam is emitted from the focal point, so it passes through the optical system. The rest becomes parallel rays as well. In this way, the beam after passing through the aspherical optical system becomes a parallel beam with a substantially circular cross section. As described above, the present invention is a waveguide type C02 laser oscillator having a rectangular cross section surrounded by two adjacent heat sink slopes and having a height ratio of about 10 tones. Since the resonator volume has a volume ratio of about 10 Pts compared to that of a normal waveguide laser, the output value is increased by about 10 Pts compared to the conventional value.

Furthermore, the present invention is capable of converting the output beam from the oscillator into a normal beam using an aspherical optical system installed at a specific position from the end of the oscillator, although the output beam from the oscillator is an irregular beam with different vertical and horizontal spot sizes and diffraction spread angles. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional waveguide laser, Fig. 2 is a perspective view of a waveguide type carbon dioxide laser oscillator according to an embodiment of the present invention, and Figs. 3a and 3b are collimator optics of the output beam of the laser oscillator. FIG. 2 is a perspective view showing the system. 11... waveguide discharge tube, 12... waveguide,
13... Output coupling mirror, 14... Total reflection mirror, 21... Waveguide discharge tube, 22... Waveguide, 23... Output Coupling mirror, 24... Total reflection mirror, 25, 26... Discharge electrode group, 31...
...Output coupling mirror, 32...Aspherical optical system, 33...
...Near field pattern, 34... Diffraction spread of the beam, 35... Collimated exit beam. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A waveguide discharge tube comprising at least a waveguide having a waveguide, an output coupling mirror, and a total reflection mirror, wherein the waveguide of the waveguide discharge tube has a rectangular cross-sectional shape, and the waveguide The horizontal length of the cross section is configured to be sufficiently longer than the vertical length, and the output coupling mirror and the total reflection mirror have a vertical curvature R_V and a horizontal curvature R_H of R.
_V=Z+(π^2d^4)/(256λ^2Z)1/
2<R_H<∝However, Z: Distance between waveguide end and reflecting mirror d: Waveguide vertical length λ: Wavelength l: Characterized by being an aspherical mirror that satisfies the relationship between the distance between the output coupling mirror and the total reflection mirror. A waveguide carbon dioxide laser oscillator. 2. The waveguide carbon dioxide laser according to claim 1, characterized in that an aspherical optical system is provided at a position where the vertical and lateral spot diameters of the beam emitted from the output coupling mirror are equal. oscillator. 3 The radius of curvature in the vertical direction of the aspherical optical system is selected to be equal to twice the distance between the output coupling mirror and the aspherical optical system, and the radius of curvature in the horizontal direction is selected so that it has no curvature. A waveguide carbon dioxide laser oscillator according to item 2.