High-average-power xenon laser

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CORRESPONDENCE

REFERENCES [I] S. N. Suchard, R.

L. Kerber, G. Emanuel, and J. S. Whittier, “Effect of Hz pressure on pulsed H, + F, laser, experiment and theory,” J . Chem. Phys.. vol. 57, pp. 5065-5075, 1972. [2] J . Wilson, D. Northam, and P.Lewis, “HF laser action above thesecond explosion limit,” presented atthe 3rd Conf.ChemicalandMolecularLasers, St. Louis, Mo., May 1-3, 1972. [ 3 ] 0. M . Batovsky. G. K. Vasil’ev, and V. L. Tal’rose,Int.Symp.Chemical Lasers, Moscow, Sept. 1969. (41 J. A. Beaulieu, “High peak power gas lasers,” Proc. IEEE, vol. 59. pp. 667-674, 1971. [ 5 ] Preliminary measurements with amixture having mole ratio F,:H,:OZ:He = I :0.2:0.08:8 haveyielded pulse energiesas large as 160 percent of the initiation energy.

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High-Average-Power Xenon Laser 0

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T. S. FAHLEN

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RUSSELLTARG

Fig. I .

Outputpowerversusrepetitionrateforapulsedxenonlaserwithtrdns\~ersegas flow.

Abstrocr-A transversely excited pulsedXelaserproducingover 10 W of average multiwavelength infrared power at a pulse repetition frequency

The optical cavity consists of a 10-m total reflector and a 40percent-reflectiveoutputmirror(bothcontainedwithinthevacuum enclosure) when multiline operation is desired. For single-line operation a diffraction grating blazed for3.75 p replaces the total reflector. Thedesignandoperation of apulsedXelasercapable of The laser has produced 1 1 W of average power when operating at producing 11 W of average infrared powera pulse at repetition fre- a P R F of 1200 Hz. At higher repetition frequencies, up to 2 kHz, the quency (PRF) ofI .2 kHz are described. This poweris more than applied voltage must be reduced to avoid arcing within the distwice that previously reported[I]. charge. The laserefficiency, Le., the ratioof laser output energy to High-PRF operationis achieved by circulating the gas in a direc- energy stored in the primary capacitor, is 0.13 percent. It is antion perpendicularto boththeelectrical dischargeand theopticaxisticipated that operation at higher pulse frequencies could be obofthelasercavityataflowvelocityupto4Om/s.Hereplasmaunifor- tained by increasing theflow velocity above the 40 m/s obtainable mity for each pulseis assured by sweeping residual metastables and withtheblowercurrentlybeingused.Fig. 1showsthedependenceof ions formed during each electrical discharge from the discharge average output power on PRF for applied voltages IO, of 16, and region before the next electrical pulse is applied. A blower and heat 20 kV. The pulsewidth is approximately 100 ns full width at halfexchanger are enclosedin the sealedsystem to recirculate and cool maximum. With no internal diffraction grating, laser osciltation thegasmixture,whichconsistsof1-2torrofXeand350-400torrof occurs at 2.03, 2.65, 3.43, and 3.65 1.The output spectrum reHe. portedhere,measuredwitha1/2-mJarrell-Ashspectrometer The discharge is formed across the 4.75-cm gap between the withan infraredgrating,correctsthespectralassignment reanode and cathode, which are 76 cmbylong about 3cm wide.The ported previously [ 1 ], which was measured using several fairly cathode is a metal bar with two insulated preionization wires runwideband filters. ning in two grooves machined along the oflength the cathode. The Single-line operationat any oneofthesewavelengths isobtained anode is aconvex metal plate. The dischargecircuit is designed to be by using an intracavity diffraction grating. In this case, thespectral oflow inductance. Energy stored in aprimarycapacitorchargedby energy distribution is46percent at 2.03y, 4 percent at 23 per2.651, a 20-kV power supply is transferred to a secondary capacitor centat3.43~,and27percentat3.65~.Althoughthegratingandoutthrough a hydrogen-thyratron switch. The laser electrodes are put coupler would allow any existing lasing action to be observed parallel with this secondary capacitor. After the thyratron switch is from 2 to5.6 p, only those lineslisted were seen. closed, a 150-ns discharge occurs across the laser when the voltage across the secondary capacitor (and, therefore, across the laser) ACKNOWLEDGMENT reachesthebreakdownvoltageofthe1asergas.Theuseofthesecondary capacitor tends to eliminate the inductance of the primary The authors wish to thank M . L. Conroyforhistechnical capacitor and thyratron switch from the laser-discharge circuit. assistance. of 1.2 kHz is described. A diffraction grating allows single-line operation at 2.03, 2.65, 3.43, or 3.65 p.

Manuscript received March 5, 1973. This work was supported by the Air Force Systems Command, under WPAFB Contract F33615-72-C-1631. T. S. Fahlen is with GTE Sylvania, Inc., Mountain View, Calif. 94040. R. Targ is with the Stanford Research Institute, Menlo Park, Calif.

REFERENCES [ I ] R. Targ and M . W . Sasnett, “High-repetition-ratexenon laserwith transverseexcitation,” l E E E J . Quanlun? Electron., vol. QE-8, pp. 166-169, Feb. 1972.