Coherent light generators – Particular active media – Gas
Patent
1982-06-04
1984-12-11
Sikes, William L.
Coherent light generators
Particular active media
Gas
372 59, 372 90, 372 61, H01S 322
Patent
active
044883102
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a continuously-excited laser, and more particularly a technique by which repetitively-pulsed outputs may be obtained from such a laser.
The invention particularly relates to producing repetitively-pulsed outputs from continuously excited gas lasers of the type in which the processes of excitation and power extraction are separate.
BACKGROUND ART
There are two main forms of lasers of this type, namely CO.sub.2 mixing lasers and supersonic CO lasers.
Common examples of CO.sub.2 mixing lasers are described in an article entitled "High-Power CO.sub.2 Electric Discharge Mixing Laser" by Clyde O. Brown and published in Appl. Phys. Lett. Vol. 17 dated November 1970 at pages 388-391, and also in a report entitled "A 30-kW CO.sub.2 Mixing Laser" by Ross C. McLeary, Russell E. Whitcher and Peter J. Beckwith and published in a Materials Research Laboratories' report MRL-R-751 dated July 1979.
It is known with such CO.sub.2 mixing lasers to, in the excitation stage, continuously excite a gas having a relatively long excitation life, and to subsequently continuously feed the excited gas into a mixing zone in the power extraction stage where it is mixed with CO.sub.2, or CO.sub.2 and He, and transfers its excitation to the CO.sub.2 which has a relatively shorter excitation life. The gas mixture subsequently passes to the resonator to produce a laser beam.
A known form of supersonic CO laser is disclosed in an article entitled "Performance of a Large, CW, Pre-excited CO Supersonic Laser" by John W. Daiber and Herbert M. Thompson and published in IEEE J. Quantum Electron, Vol. QE-13, dated January 1977 at pages 10 to 17. It is known with such supersonic CO lasers to continuously excite CO in the excitation stage. CO, which has a relatively long excitation life, is continuously fed under supersonic conditions to the resonator of a cooled power extraction stage to produce a laser beam.
DISCLOSURE OF THE INVENTION
We have found that if, instead of continuously transferring the excited gas from the excitation stage to the power extraction stage, the excited gas is supplied in the form of a series of pulses, the system is simpler than conventional methods of producing repetitively pulsed outputs.
The basis of the present invention rests with supplying the power extraction stage with a series of pulses of excited gas corresponding to the required train of output pulses. The excitation of the gas in effect takes place between the transfer of pulses and the technique is most efficient in situations where the gas being excited has a relatively long excitation life compared with the interpulse (storage) time and when the injection time for the pulses of gases into the power extraction stage is short compared with the interpulse time. If the above conditions are satisfied the ratio of pulse-power output to the equivalent CW output would approximate the ratio of interpulse (storage) time to the injection time.
The invention may therefore envisage a method of obtaining a repetitively-pulsed output from a continuously excited gas laser, said method comprising continuously producing, in an excitation zone, a stream of excited gas of a type having a relatively long excitation life, storing such excited gas and subsequently transferring said gas, in the form of pulses, to a power extraction zone incorporating a resonator.
In the case where the gas laser is a CO.sub.2 mixing laser the gas which is excited in the excitation zone is, after storage, transferred in pulses to a mixing region in the power extraction zone and in which it is mixed with CO.sub.2 to transfer its excitation thereto prior to the mixture flowing into the resonator. Preferably the gas is N.sub.2.
In the case where the gas laser is a supersonic CO laser, the CO gas itself is excited in the excitation zone and is, after storage, transferred under supersonic conditions to the resonator in the power extraction zone.
The invention also envisages a continuously excited gas laser for producing a repetitively-pulsed output in acc
REFERENCES:
patent: 3302127 (1967-01-01), Shao-Chi Lin
patent: 3496489 (1970-02-01), Shao-Chi Lin
patent: 3571747 (1971-03-01), Bronfin et al.
Beckwith Peter J.
McLeary Ross C.
Clarke Dennis P.
Scott, Jr. L /e/ on
Sikes William L.
The Commonwealth of Australia
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