Pulsed gas lasers

Details Pulsed gas lasers Pulsed gas lasers

1996-03-26

1997-11-04

Scott, Jr., Leon

Coherent light generators

Particular component circuitry

Optical pumping

372 55, 372 33, H01S 300

Patent

active

056848145

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to pulsed gas lasers such as recombination lasers and transverse excited atmospheric (TEA) lasers. Such recombination lasers are a class of gas lasers and derive most of the excitation of lasing action from recombination of ions following ionisation of a gas by an electrical discharge. Descriptions of recombination lasers are found for example in: V V Zhukov, E L Latush, V S Mikhalenskin, M F Sem, Sov J Quantum Electron 7, 704 (1977); and descriptions of TEA lasers are in: F Collier, B Lacour, M Maillet, M Michon, J Appl Phys 52 (10), Oct 1981; and RSRE Memo 4384, authors R C Hollins, D A Orchard, and A S Swanson, available from DRIC UK.
2. Description of Prior Art
A typical recombination laser comprises a cooled tube through which a gas mixture, eg of He-Xe, or xenon, is flowed. At each end of the tube are electrodes connected to capacitors. Adjacent the tube ends are mirrors, one a completely reflecting mirror, the other a partial reflector forming a light output window. Rapid discharging of the capacitors causes ionisation of the laser gas in the tube to energy levels above a lasing energy level. After the electrical discharge pulse ends, the excited gas recombines and emits light. For a He-Xe gas this light has lines at 2.03, 2.65, 3.43, and 3.65 .mu.m, ie in the so called mid infra red wavelengths.
One type of pulsed gas laser is described in Patent Abstracts of Japan Vol 15, No 258 (E-1084) 28-06-1991 and Japan-A-3083384. Improved electrode lifetime is provided by connecting the cathode of a diode to the abode of the main discharge electrode, and the anode of the diode to the cathode of the discharge electrode. The purpose of the diode is to prevent arc generation, with consequential surface pitting damage, between the discharge electrodes caused by reverse voltages.


SUMMARY OF THE INVENTION

The present invention improves the amount of laser light emitted by a recombination laser after the electrical discharge pulse has ended.
The invention may also improve the efficiency of other gas lasers by removing current oscillations in the laser gas after the initial lasing pulse is completed and retaining electrical energy in the circuits for the next discharge pulse.
The invention may also improve the pulse repetition frequency (prf) from a typical value of less than 10 Hz to about 20 kHz in some constructions of gas lasers.
According to this invention the laser light output is improved by preventing electrical current oscillations in the laser gas after the initial electrical discharge pulse has ended, by use of rectifying diodes in the electrical circuit supplying the discharge pulse.
According to this invention a recombination pulsed gas laser comprises: the laser tube to define a laser cavity, electrodes,
Characterised by diodes arranged in series and parallel with the electrodes to prevent electrical current within the laser tube after the end of the initial electrical pulse.
According to an aspect of this invention the prf is increased by use of a narrow bore quartz laser tube and sub-atmospheric gas pressure.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only with reference to the accompanying drawings of which:
FIG. 1 is a cross sectional view of a He-Xe gas recombination laser.
FIG. 2 is a block diagram of the laser of FIG. 1 showing electrical control circuitry.
FIGS. 3 to 6 are wavetraces showing laser output for different control circuitry.
FIG. 7 is a block diagram of a TEA laser showing electrical control circuitry.


DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIG. 1 a recombination laser comprises a quartz tube 1 surrounded by a jacket 2 with an annular space between the tube 1 and jacket 2. Inlet 3 and outlet 4 end structures support and locate the tube 1 and jacket. Cooling water inlet 5 and outlet pipes 6 are formed on the jacket 2 so that coolant may be flowed through the annular space and keep the tube 1 at a desired temperature.
The inlet end stru

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