GB2145274A

GB2145274A - Gas laser system

Info

Publication number: GB2145274A
Application number: GB08417276A
Authority: GB
Inventors: Minoru Suzuki; Chikara Yamaguchi
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1983-07-27
Filing date: 1984-07-06
Publication date: 1985-03-20
Also published as: JPS6028287A; GB8417276D0; DE3427424A1; GB2145274B

Abstract

A gas laser system provided with an output mirror (15) and a rear mirror (16) in a hermetically sealed vessel (1), in which a pair of folding mirrors (17, 18) are disposed in an optical path between the output mirror and the rear mirror, and each folding mirror has a hole or recess (25, 25A) which allows the generated laser beam to pass along the optical path for laser resonating between the output and rear mirrors via the folding mirrors. According to this configuration, the widthwise dimention of the laser system can be reduced. <IMAGE>

Description

SPECIFICATION Gas laser system The present invention relates to a laser beam generating apparatus using a gaseous lasing medium, and more particularly to an improvement in folding mirrors disposed in the above apparatus.

In a laser beam generating apparatus using a gaseous lasing medium (hereinafter simply referred to as a "gas laser"), a glow discharge is generated in a lasing region which contains a gas mixture (for example, a helium-nitrogen-carbon dioxide mixture), to excite the gas mixture, thereby producing laser light. The laser light resonates with an optical cavity formed by a plurality of mirrors which are provided in the lasing region, and is then taken out from the cavity through an output mirror to perform such works as the cutting and welding of an iron plate or the like. In such cutting orwelding works, it is desirable to make the cutting or welding width as small as possible, since precise working can be done and thus the laser working is applicable to various goods.The working width can be made small by using a laser beam having the so-called single mode characteristic. In the single mode characteristic, the energy density on the center portion of the laser beam spot is far greater than the energy density at a pheripheral of the center portion. In order to obtain the single mode characteristic, it is required to make large the spacing length of optical cavity mirrors for laser light. To this end, a pair of folding mirrors are provided to face each other with the lasing region between them so as to make the laser light traverse in the excited lasing region several times. In such a structure, however, the width of each folding mirror becomes large, and it is required to make the lasing region wide. Thus, the gas laser system is obliged to become large in size.

It is accordingly an object of the present invention to provide a gas laser system which is smaller in its widthwise dimension than the conventional gas laser system.

According to the present invention, there is provided a gas laser system in which each of folding mirrors has an empty portion free to pass a laser beam between an output mirror and a rear mirror, and an optical path is laid through the empty portion thereby to reduce the width of the laser.

The present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 is a perspective, schematic view showing an embodiment of a Transverse Gas Flow type gas laser according to the present invention; Figure 2 is a diagrammatic view for explaining the embodiment shown in Figure 1; Figure 3 is a sectional view for explaining the structure of the cavity portion shown in Figures 1 and 2; Figures 4Aand 4B are front and horizontal sectional views of the first folding mirror and others shown in Figures 1,2 and 3, respectively; and Figures 5Aand5B are front and horizontal sectional views of the first folding mirror and others included in another embodiment of a gas laser according to the present invention.

Now, an embodiment of a Transverse Gas Flow type gas laser according to the present invention will be explained below, with reference to Figures 1,2 and 3.

Referring to Figures 1,2 and 3, the above gas laser is provided with a hermetically sealed steel vessel 1, and the inside of the vessel is formed mainly of a circulating duct 2 and an optical cavity portion 3.

The circulating duct 2 is provided with a blower motor 5 for causing a gas mixture 4 to circulate in a direction as indicated with an arrow (namely, in a direction A), and a heat exchanger 6. Both ends of the duct 2 communicate with side faces of the cavity portion 3.

A cathode 8 and an anode 7 are disposed at the top and bottom of the cavity portion 3, respectively.

Holding plates 12 and 13 are attached through a bellows 11 to the left and right walls of the cavity portion 3, respectively. Further, an output mirror 15 and a rear mirror 16 are attached through a bellows 14 to the outer surfaces of the holding plates 12 and 13, respectively. First and second folding mirrors 17 and 18 are mounted through a mounting member 19 on the inner surfaces of the holding plates 12 and 13, respectively, so as to be adjacent to the output mirror 15 and rear mirror 16, respectively. The first and second folding mirrors 17 and 18 are fixed to the mounting members 19 so that the reflective surfaces of the folding mirrors 17 and 18 are slanting and facing each other, and are assembled as shown in Figures 4A and 4B.Since the folding mirrors 17 and 18 are substantially identical in structure, only the first folding mirror 17 is shown in Figures 4A and 4B, and explanation of the second folding mirror 18 will be omitted.

Referring to Figures 4A and 4B, one end of a supporting plate 20 is supported by the mounting member 19, and the first folding mirror 17 is interposed between the supporting plate 20 and a clamping member 22 in such a manner that a sealing ring 21 is provided between the folding mirror 17 and supporting plate 20. A bolt 23 is inserted into the clamping member 22 and supporting plate 20, and then turned to hold the first folding mirror 17 between the supporting plate 20 and clamping member 22. The heat generated at the first folding mirror 17 can be cooled down by water flowing through a coolant path 24 which is provided in the clamping member 22, in the direction as indicated with an arrow. The first folding mirror 17 has a recession 25.The recession 25 is provided in those portions of the first folding mirror 17, supporting plate 20 and clamping member 22 which are adjacent to an optical path 30A passing through the output mirror 15.

When a d.c. voltage is applied between the anode 7 and cathode 8, a glow discharge is occured between these electrodes, and the gas mixture 4 is excited. Thus, an excited lasing region 31 is formed, and laser light 30 is generated. The laser light 30 resonates with an optical cavity formed by the output mirror 15, first folding mirror 17, second folding mirror 18 and rear mirror 16, and thus five optical paths 30A to 30E are formed in the cavity as shown in Figure 3. The optical path 30A passes through the recession 25 as shown in Figures 4A and 4B. Further, the recession 25 is provided in the first folding mirror 17, supporting plate 20 and clamping member 22, in close proximity to the optical paths 30B and 30C which are adjacent to the optical path 30A.Accordingly, the spacing between the optical path 30A and optical path 30B (or 30C) can be made small. In other words, the output mirror 15 can be disposed in close proximity to the optical paths 30B and 30C. Similarly, the spacing between the optical path 30E and optical path 30C (or 30D) can be made small by providing another recession 25 in the second folding mirror 18 and others. Thus, the spacing L between the optical paths 30A and 30E can be reduced by an amount corresponding to the displacement of the optical paths 30A and 30E toward the central optical path 30C. Accordingly, the optical paths 30A to 30E can be disposed in a narrow lasing region, and thus the embodiment shown in Figures 1 to 3 can be made small in size without reducing the luminous efficiency.

The recession 25 provided in each of the folding mirrors 17 and 18, supporting plates 20 and clamping members 22 is always disposed on the output mirror side or on the rear mirror side, and therefore can act as a mark for positioning. Thus, a positioning operation can be readily performed, and a time required for assembling the cavity portion can be shortened.

Figures 5A and 5B show the first folding mirror included in another embodiment of a gas laser according to the present invention. Referring to Figures 5A and 5B, a through hole 25A is provided in each of the first folding mirror 17 and supporting plate 20 at a position adjacent to the optical paths 30B and 30C, to make small the spacing the optical path 30A and optical path 30B (or 30C). Similarly, another through hole 25A is provided in the second folding mirror 18 and the supporting plate fixed thereto, to make small the spacing between the optical path 30E and optical path 30C (or30D).Thus, the spacing between the optical paths 30A and 30E can be reduced.

In the above-mentioned embodiments, circular folding mirrors have been used. However, square or rectangular folding mirrors may be used in place of the circular folding mirrors. The present invention is also applicable to another Transverse Gas Flow type gas laser in which two of the transport direction of gas mixture, the discharge direction and the propagation direction of laser light are parallel to each other and are perpendicular to the remaining one, or an axial-flow type gas laser in which all of the above-mentioned directions are parallel to each other. The present invention is further applicable to a sealed gas laser in which a gas mixture does not circulate.

As has been explained in the foregoing, according to the present invention, a gas laser can be fabricated which is made small in size.

Claims

1. A gas laser including a hermetically sealed vessel containing a gas mixture, a cathode and an anode each provided in said hermetically sealed vessel, an output mirror and a rear mirror provided at opposite ends of said hermetically sealed vessel, and first and second folding mirrors facing each other and provided in close proximity to said output and end mirrors, respectively, to generate a glow discharge between said cathode and anode, to excite said gas mixture by said glow discharge, to make laser light generated by the excited gas mixture resonate with said mirrors, and to take out a laser beam through said output mirror, wherein a empty space for transmitting said laser light is provided in a portion of said first folding mirror corresponding to said output mirror and a portion of said second folding mirror corresponding to said rear mirror.

2. A gas laser according to claim 1, wherein said empty space is given by a recession.

3. A gas laser according to claim 1, wherein said empty space is given by a through hole.

4. A gas laser according to any one of claims 1 and 2, wherein said gas laser is a Transverse Gas Flow type gas laser.

5. A gas laser according to any one of claims 1 and 2, wherein said gas laser is an axial-flow type gas laser.

6. A gas laser according to any one of claims 1 and 2, wherein said gas laser is a sealed gas laser.

7. A gas laser substantially as hereinbefore described with reference to, or as illustrated in Figures 1 to 4B; or Figure 5 of the accompanying drawings.