GB1564863A

GB1564863A - Gas laser tube system

Info

Publication number: GB1564863A
Application number: GB672477A
Authority: GB
Original assignee: LASER LIGHT GmbH
Current assignee: LASER LIGHT GmbH
Priority date: 1976-02-23
Filing date: 1977-02-17
Publication date: 1980-04-16
Also published as: DE2607333B2; FR2341968B1; FR2341968A1; DE2607333C3; DE2607333A1

Description

(54) GAS LASER TUBE SYSTEM (71) We, "LASER-LIGHT" GESELL SCHAFT MIT BESCHRANKTER HAFTING, a Company organised under the laws of West Germany, of Grusonstrasse 55, 2000 Hamburg 74, West Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a gas laser coaxial tube system. According to the present invention a gas laser glass coaxial tube system comprises a capillary tube disposed within, and at a distance from, an intermediate tube which is in turn disposed within an outer tube, wherein the intermediate tube is connected at one end to the inner end of the capillary tube and at the other end to the outer tube.

Tube systems of this kind comprising a capillary tube, the inner end opening to an outer annular space bounded by an outer tube surrounding the capillary tube, a transverse wall disposed at a distance in front of the inner end of the capillary tube, and a seal opposite the transverse wall and connecting the capillary tube to the outer tube, one mirror of the tube system being secured to that end of the capillary tube which projects beyond the seal and the other mirror being secured to the transverse wall are known, e.g. from Figure 3 of U.S. Patent Specification No. 3,787,780. In this system, the seal is constructed as an annular wall firmly secured both to the outer tube and the capillary tube.In this, and in other known constructions in which the capillary tube is secured in the spaced transverse walls of the outer tube, it can be very difficult during the manufacturing process to ensure that the two resonator mirrors are made parallel with the required high degree of accuracy. Practical tests are required to find whether the parallel positioning is accurate, and a great deal of wastage in the manufacture of such tubes can result.

In other known constructions, the capillary tubes are closed at the end by a clear glass plate or, e.g. a Brewster window, and a mirror is secured to the tubes via adjusting means at the same place. The mirror can be adjusted during operation, but is easily put out of order, e.g. by contamination, impacts and the like. The mirror is usually mounted on a flexible metal tube which, in the case of conventional glass tube systems, requires glass-metal junctions, with the result that the tube system is expensive and fragile.

In the prior art relating to parallel arm laser tube systems, in which the outer tube is disposed parallel to and at a distance from the capillary tube, there is a much more advantageous method of adjustment, particularly for mass production. The resonator mirrors are secured to the end of the capillary tubes and roughly adjusted. After the tube system has been put into operation, fine adjustment is brought about by a spac- ing device connected to the free ends of the capillary tube and the outer tube. During the fine adjustment, the capillary tube is slightly bent until the mirrors are parallel.

The main disadvantage of parallel arm tubes is their great bulk and their thermal instability, resulting from their asymmetrical construction.

The present invention seeks to provide a gas laser glass coaxial tube system which obviates these difficulties which is easy to manufacture and which provides a simple method of finely adjusting the parallel position of the resonator mirrors.

The tube system according to the invention can easily be constructed from glass in the normal manner, by glass-blowing, the tubes being subsequently secured together at their ends. It is not necessary to centre the tubes exactly. The resonator mirrors can be secured in known manner after rough adjustment.If fine adjustment of the mirrors is required this can be brought about by a modification of the method used for the fine adjustment of parallel arm tubes, by varying the position of the free end of the capillary tube in relation to the interconnected ends of the intermediate tube and the outer tube, and thus avoiding the need for conventional auxiliary devices such as those for clamping the entire tube system in an auxiliary frame or at the end of the capillary tube or at an adjustable mirror holder disposed at the transverse wall sealing the outer tube, the use of which can be very sensitive to heat.

The cost of manufacturing tube systems of this kind can be greatly reduced without sacrificing advantages of coaxial laser tubes, such as their favourable outer dimensions.

One advantage over parallel arm tubes is that bending of the capillary tube during fine adjustment is avoided, or at least minimised. Instead of in the thick-walled capillary tube, the bend is made in the joint between the intermediate tube and the capillary tube or in the intermediate tube itself, so that the capillary tube remains substantially straight, thus reducing the effect of bending caused by heating during operation.

In addition, the tube system according to the invention has better thermal stability because of its symmetrical structure.

The tube system of the invention may be provided with a spacing and mounting means for fine adjustment of the system disposed between the capillary tube and the intermediate tube adjacent that end of the intermediate tube which is connected to the outer tube, i.e. adjacent the joint between those tubes. In this position, it is protected from disturbance and does not increase the bulk of the tube system, more particularly its outer diameter, which is important.

The spacer and mounting means may comprise peripherally adiustable means which, at any reauired angular position, can be used for adjusting the radial spacing between the two tubes. In this manner, when the tubes are to be finely adiusted, the desired direction and extent of the adjustment can be very rapidly determined, thus greatly reducing the time required for fine adiustment as a result of the systematic operation.

The mounting means may comprise a wedge which can be driven into the intermediate space. A wedge of this kind, which can be driven to the required depth at the required peripheral position and subseouentlv secured. e.g. by adhesion, provides a simple and economic method of fine adiustment.

The tube system of the invention may further be Drovided with a capillarv tube portion in line with the capillary tube disposed in the transverse wall and which bears a resonant mirror at its outer end. The capillary tube portion can be used in a particularly simple manner for securing the resonator mirror. More particularly, the same method of securing and the same type of mirror can be used at both ends. In addition, the capillary tube portion prolongs the cavity resonator and thus makes it easier to control or influence the modes occurring in the cavity resonator.

The further capillary tube portion may also bear a Brewster window at its inner end. An additional Brewster window for polarising the beam can be fitted in a very simple, economic manner, using the same construction.

The invention may be performed in various ways and an embodiment will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial section of a gas laser glass coaxial tube system along line I-I in Figure 2, and Figure 2 is a section along line II-II of the tube system of Figure 1.

The drawings show a glass laser tube system. As Figure 1 shows, the inner end of a capillary tube 1 is secured to an intermediate tube 2, which is coaxially aligned with tube 1 and, at the junction 3, merges into the wall of the capillary tube 1 by means of an inner curve which can be produced by glass-blowing. The other end of tube 2 is curved outwardly at 4 and secured to the end of a concentrically disposed outer tube 5. The latter junction can also be produced by glass-blowing.

At an axial distance from the inner end of tube 1, the outer tube 5 coaxial with the tubes 1 and 2, is sealed by a transverse wall 6 in which a further capillary tube portion 7 is disposed in axial alignment with tube 1. At its inner end, tube portion 7 carries a Brewster window 8 disposed at a Brewster angle of approximately 55" to the tube axis.

A resonator mirror 9 is disposed at the outer end of capillary tube 1, and a mirror 10 is disposed at the outer end of tube portion 7.

A cylindrical cathode plate 11 is disposed in coaxially with and between the outer tube 5 and the intermediate tube 2. The plate 11 abuts the transverse wall 6 at one end and the other end is located by constrictions 12 in the outer tube 5. Between the constrictions 12 and the end of the outer annular chamber at 4, there is space for additional devices (not shown) such as getter systems and the like. The cathode plate 11 is electrically connected to a conductor wire 13 extending through the outer tube 5. An anode wire 14 is guided through the wall of tube 1 near mirror 9. The gas discharge for exciting the laser effect occurs between the anode 14 and the cathode plate 11, i.e. in the important region of the capillary tube, which is shortened in Figure 1.

A frusto-conical ring 16 is fitted over the tube 1 at the open end of the space 15 between tube 1 and tube 2. A wedge 17 is slidably disposed on the ring 16 to form together an adjusting device.

The tube system is manufactured in conventional manner. Before the transverse wall 6 is attached to the tube 5 the cathode plate 11 and the getter system or the like are inserted, and the Brewster window 8 is secured to the tube portion 7 already disposed in the wall 6.

After the tube system has been finished, mirrors 9 and 10 are fitted, roughly adjusted and then secured, e.g. by adhesion. The tube system is cleaned, filled with gas and put into operation. During operation, wedge 17 is driven into the intermediate space 15, while the laser beam is observed.

If the observed change does not correspond to the desired change in the beam image, the adjusting device is rotated around the capillary axis until the desired angular position is obtained. The wedge 17 is then moved in the axial direction until the correct adjustment is obtained.

The wedge 17 and the conical ring 16 can be constructed as a permanently-connected unit which is secured by adhesion after the adjustment process. Alternatively, parts 16 and 17 can be connected by suitable mechanical adjusting devices such as screws. In the simplest embodiment, a wedge can be used alone and simply driven between the intermediate tube 2 and the capillary tube 1.

WHAT WE CLAIM IS: 1. A gas laser glass coaxial tube system comprising a capillary tube disposed within, and at a distance from, an intermediate tube which is in turn disposed within an outer tube, wherein the intermediate tube is connected at one end to the inner end of the capillary tube and at the other end to the outer tube.

2. A tube system as claimed in Claim 1, wherein spacer and mounting means are disposed between the capillary tube and the intermediate tube adjacent the said other end of the intermediate tube.

3. A tube system as claimed in Claim 2, wherein the spacer and mounting means comprise peripherally adjustable means which, at any required angular position, can be used to adjust the spacing between the capillary tube and the intermediate tube.

4. A tube system as claimed in Claim 2 or Claim 3 wherein the spacer and mounting means comprises a wedge which can be driven into the space between the capillary tube and the intermediate tube for adjustment thereof.

5. A tube system as claimed in any of the preceding claims wherein a further capillary tube portion in linear alignment with the said capillary tube is disposed in a transverse wall disposed across the outer tube at a distance from the said inner end of the capillary tube.

6. A tube system as claimed in Claim 5 wherein resonator mirrors are secured to the outer end of the capillary tube and to the outer end of the said further capillary tube portion.

7. A tube system as claimed in Claim 5 or Claim 6 wherein the inner end of the said further capillary tube portion bears a Brewster window.

8. A gas laser glass coaxial tube system comprising a capillary tube, the inner open end of which is connected to an outer annular space bounded by an outer tube surrounding the capillary tube, a transverse wall disposed at a distance in front of the inner end of the capillary tube, and a seal opposite the transverse wall and connecting the capillary tube to the outer tube, one mirror of the tube system being secured to that end of the capillary tube which projects beyond the seal and the other mirror being secured to the transverse wall, characterised in that the seal comprises an intermediate tube surrounding and at a distance from the capillary tube disposed inside the outer tube and connected at one end to the inner end of the capillary tube and at the other end to the outer tube.

9. A tube system substantially as described herein with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. slidably disposed on the ring 16 to form together an adjusting device. The tube system is manufactured in conventional manner. Before the transverse wall 6 is attached to the tube 5 the cathode plate 11 and the getter system or the like are inserted, and the Brewster window 8 is secured to the tube portion 7 already disposed in the wall 6. After the tube system has been finished, mirrors 9 and 10 are fitted, roughly adjusted and then secured, e.g. by adhesion. The tube system is cleaned, filled with gas and put into operation. During operation, wedge 17 is driven into the intermediate space 15, while the laser beam is observed. If the observed change does not correspond to the desired change in the beam image, the adjusting device is rotated around the capillary axis until the desired angular position is obtained. The wedge 17 is then moved in the axial direction until the correct adjustment is obtained. The wedge 17 and the conical ring 16 can be constructed as a permanently-connected unit which is secured by adhesion after the adjustment process. Alternatively, parts 16 and 17 can be connected by suitable mechanical adjusting devices such as screws. In the simplest embodiment, a wedge can be used alone and simply driven between the intermediate tube 2 and the capillary tube 1. WHAT WE CLAIM IS:

1. A gas laser glass coaxial tube system comprising a capillary tube disposed within, and at a distance from, an intermediate tube which is in turn disposed within an outer tube, wherein the intermediate tube is connected at one end to the inner end of the capillary tube and at the other end to the outer tube.