JPS58169983A - Discharge tube excitation laser device - Google Patents

Abstract

PURPOSE:To equalize the gain within the cross-section of an activated substance by a method wherein the shape of a reflection cylinder is formed into an elliptic or a twin- elliptic cylinder, and this reflection cylinder is formed into an uneven surface with diameter and depth specified for the wavelength of excited light, in a laser device constituted of a laser activated substance, a discharge tube, and reflection cylinders which focus the light from the discharge tube to the activated substance. CONSTITUTION:The half cuts of two elliptic cylinders are formed respectively on one surface of two reflection cylinders 3, then the reflection cylinders 3 are contacted close while fitting these each other, and the reflection surface wherein the central end parts are overlapped is generated therebetween. Next, the laser activated substance 1 is inserted into the center thereof, then flash lamps 2 are arranged on the both sides thereof, and the focal line 5 of each lamp 2 is used for the focus of one side, and the focal line 6 of the activated substance 1 for the focus of the other side. In this constitution, the reflection line is not finished in a mirror surface, but formed into a reflection surface 4a in uneven form with the diameter 1,000-10,000 times and the depth 10-300 times larger than the wavelength of the excited light. Thus, the light from the lamp 2 is evenly irradiated onto the activated substance 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge tube excitation laser device such as a flash lamp excitation laser device that oscillates or increases the intensity of laser light, and particularly relates to a rod-shaped laser device which is an active material of the discharge tube excitation laser device. This invention relates to homogenizing the gain distribution within the cross section of a laser active material in the form of a liquid solution.

Conventionally, in this type of discharge tube pumped laser device, the reflective surface is used as a ninth reflecting tube to effectively focus the light from a good flash lamp (discharge tube) that excites the laser active material onto the laser active material. Since a mirror surface is used, the gain distribution within the cross section of the laser active material is generally high at the center. Because of this, in devices that use multiple amplifiers connected in series, even if the intensity distribution of the laser light incident on the subsequent amplifier is uniform, the intensity distribution of the laser light emitted from the amplifier may be uneven, or the intensity distribution may be uneven in the center. This has the drawback of increasing the intensity of the laser and destroying the laser active material or the optical components used by inserting it into the optical path.

Hereinafter, a conventional flash lamp excitation laser device will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing an example of a pump cavity for optically pumping a conventional flash lamp excitation laser device, in which 1 indicates a laser active material;
2 is a flash lamp, and 3 is a reflecting tube, which has a reflecting surface 4 inside. 5 is the first focal line of the reflective surface, and 6 is the second focal line. The cross-sectional shape of the reflecting surface is a biellipse with the second focal line 6 as one focal point and the other focal point as the first focal line, and its surface is finished to a mirror surface. Further, the first focal line is the center of the flash lamp 2, and the second focal line is the center of the laser active substance 1.

In such a configuration, the light from the flash lamp 2 is divided into light that directly enters the laser active material 1 and light that is reflected by the reflective surface 4 and enters the laser active material 1 .

FIG. 2 shows an example of light rays in the cross section of the reflector tube. Here, 7 is the direct light from flash lamp 2, 8
is the reflected light reflected by the reflective surface 4. Since the laser active substance 1 and the flash lamp 2 are located on the focal line of the reflecting surface 4, as shown in the cross-sectional view of FIG.
[The reflected light 8 reflected by i4 becomes a beam that passes through the center of the laser active material 1 on the other focal line. Similarly, if the light reflected elsewhere on the reflective surface 4 passes through the center of the laser active material 1, the light U of the flash lamp 2 will pass through the center of the laser active material 1.
The cross section of the laser active material has a non-uniform gain distribution in which the gain is high at the center and low at the periphery.

FIG. 3 shows the measured values of this non-uniform gain distribution. In this figure, numbers 1 to 5 indicate the measurement points of the laser active substance 1, and numbers 4ii11 to 5 indicate the gain (relative value).
5 correspond to each other. As is clear from this figure, the gain at the center of the laser active shed is about twice as high as the gain at the periphery.

As described above, when the reflective surface 4 is mirror-finished and has a reflective orientation, the gain distribution in the cross section of the laser active material becomes extremely non-uniform, resulting in non-uniform intensity distribution of the emitted laser beam after amplification. It had the disadvantage of giving.

This invention was made to eliminate these drawbacks, and by using a reflective surface with an uneven surface without changing the average shape of the reflective surface instead of a mirror-finished reflective surface, It is an object of the present invention to provide a discharge tube pumped laser device in which the gain is made uniform within the cross section of a laser active material.

Embodiments of the present invention will be described below using a seven-lash lamp excitation laser device.

FIG. 4 shows an embodiment of the present invention, which has the same configuration as the pump cavity of the conventional flash lamp excitation laser device shown in FIG. 1 except for the uneven reflecting surface 4a, and the same parts are denoted by the same reference numerals. It is attached.

FIG. 5 shows details of the uneven reflecting surface 4a. The average shape of the reflecting surface of the uneven reflecting surface 4a is a biellipse, but the surface has a 1000° angle with respect to the wavelength of the excitation light.
It has unevenness with a diameter of 10 to 10,000 times and a depth of 10 to 300 times.

By using such an uneven reflecting surface 4m, the gain distribution in the cross section of the laser active material can be made uniform.

Next, the effect of the uneven reflecting surface 4a will be explained in detail with reference to FIG. 6, which shows an example of light rays from a flash lamp in the cross section of the reflecting tube. Emitted from flash lamp 2,
When the light reaches the uneven reflecting surface 4a, there are some places in the reflection direction that are slightly concave and convex from the bielliptical direction, so the light 81 is reflected at the concave places and the light 81 is reflected at the convex points at important points. The light 8b is reflected by the light 8b. Since these reflected lights 8a and 8b are reflected in different directions, they are incident on different places on the laser active substance l, and the flash lamp 2
The beam of light produces an effect of uniformly irradiating the laser active material 1t, and produces a uniformizing effect such that the gain value in the cross section of the laser active material 1 is the same both at the center and at the periphery.

FIG. 7 shows the measured values of the gain distribution in the case of having the uneven reflecting surface 4a as in the embodiment according to the present invention. In this diagram,
Numbers 1 to 5 indicating the measurement points of the laser active substance 16 Gain (
Solid lines 1 to 5 indicating relative values correspond to each other.

As is clear from this figure, the effect of making the gain distribution uniform when using the single uneven reflection direction 4a is large, and the gain at the center and the gain at the periphery of #1 are almost the same.

As explained above, according to the configuration of the embodiment, the reflection tube 3 condenses the light of the flash lamp 2 onto the laser active material 1.
Since the uneven reflecting surface 4a is used, the gain distribution in the cross section of the laser active material can be effectively made uniform, and the disadvantage of destruction of optical components can be eliminated.

In addition, although the description of the above embodiment does not specify a specific example of the laser active material of the flash lamp excitation laser device, an example is Nd:YAG single crystal in which neodymium ions are mixed into YAG, Another example is a dye solution in which rhodamine 6G dye or the like is dispersed in ethyl alcohol, and yet another example is a molecule of iodine sealed in a glass tube. (9) Although the above explanation has been given for the case where a flash lamp is used as an excitation source, this invention is not limited to this, and can also be applied to a lamp that continuously emits light. In such a pre-discharge pumping laser device, the average shape of the reflection surface is not changed and the gain distribution within the cross section of the laser active material is made uniform by using a reflection surface with unevenness on the surface as the reflection direction of the reflection tube. It has an effect that can be

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the pump cavity of a conventional 7 Lassie lamp pumped laser device, Fig. 2 is a cross-sectional view of the same, and Fig. 3 is an explanation showing an example of measurement of the gain distribution in the laser active material of a conventional flash lamp pumped laser device. 4 is a perspective view showing an embodiment of the discharge tube pumped laser device according to the present invention in the case of a 7-lash lamp pumped laser device, and FIG. 5 shows details of the reflective surface portion of the reflector tube in FIG. 4. 6 is a sectional view of the embodiment of FIG. 4, and FIG. 7 is an explanatory diagram showing an example of measurement of the gain distribution in the cross section of the laser active material in the embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Laser activity/substance, 2... Fludge, lamp, 3... Reflector tube, 4... Reflective surface, 4a... Uneven reflecting surface, 5... First focal line, 6 ...Second focal line, 7.
...Direct light, 8°5a, 8b...Reflected light. 447 Figure 2 i :i, 1 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) In a discharge tube excitation laser device that performs laser oscillation or amplification and includes a laser active material, a discharge tube, and a reflection tube that focuses light from the discharge tube onto the laser active material, the reflection tube has an average shape. It is characterized by having an elliptical cylinder or a bielliptic cylinder, and more specifically, it is equipped with a reflective surface having irregularities having a diameter of 1000 to 10,000 times and a depth of 10 to 300 times the wavelength of the excitation light. A discharge tube pumped laser device.