CORRESPONDENCE 553 from x = 0.2 to x = 2.0 in. The rotational temperatureincreases from TH- 350 K at x = 0.2 in to TR N 650 K at x = 1.0 in. The variation of ,degree of inversion,and rotational tem- perature withstreamwise distance is consistentwith expecta- tions. H ACKNOWLEDGMENT The assistance of J. Beggsin carrying out the experimental work is greatly appreciated. 1 REFERENCES Fig. 1. Dye pumped bypulsed Xe laser. [I] D. J. Spencer, H. Mirels, T. A. Jacobs, and R. W. F. Gross, “Preliminary per- formance of a CW chemicallaser,” Appl. Phys.Lert., vol. 16,p. 235,1970. [2] H. G. Heard, LaserParameter Measurements Handbooks. New York: Wiley, 1968. TABLE I [3] M. A. Kwok, D. J. Spencer, and R. W. F. Gross, “HF chemiluminescence from a reacting supersonic jet,” Ed/. Amer. Phys. Soc.. vol. 17, p. 67, 1972. Peak Pulse Wavelength [4] R. A. Meinzer, United Aircraft Res. Lab., private communication. Power Length Bandwidth Gain [5] D. J. Spencer, H. Mirels, andD. A. Durran, “Performance of a CW HF (ns) (nm) with N, or He diluent,” J. Appl. Phys., vol. 43, p.1151-1157, (W) (%I Mar. 1972. [6] W. S. King and H. Mirels, “A numerical study of a diffusion type chemicalion Xenon 300 300 laser,” Amer. Inst. Aeronaut. Astronaut., Paper 72-146. laser (pump) total, (8 nF) [7] J. Goldhar, R. M. Osgood, Jr., and A. Javan, “Observation of intense 1 50 450 superradiant emission in the high gain infrared transitions of HF and DF used (12 nF) molecules,” Appl. Pbys.Lett., vol. 18, Mar. 1971. [SI R. L. Varwig, the Aerospace Corp., private communication. Rhodamine 12 150 570, > 30 6G (8 or (8 nF) < 10 12 nF) 300 (12 nF) Simple Dye Laser Repetitively Pumped violet Cresyl 150 20 660, > 25 (8 or (8 nF) < 10 by a Xenon Ion Laser 12 nF) 300 (12 nF)

20 percent. Inthe xenon laser output, eight strong lines appear at Abstrucr-A rhodamine 6G laserand a cresylviolet laser emit light the wavelengths 430.6,495.4, 500.8, 519.0, 526, 535.3, 539.5, and pulses of0.3-ps pulse length and 10-20W peak powerat arate of 120Hzwhen 595.6 nm [5] sometimes acconfpanied by weaker ones. About pumped with an inexpensive xenon ion laser. half of the total peak output power of 300 W is distributed among the four lines. The dyelaser is similar to CWdye laser devices and consists of While numerous laser-pumped dyelasers have been described a dye cell, 1 mm inthickness, which is inserted at Brewster’s in the literature, little attention hasbeen paid to thepulsed xenon angle into an astigmatically compensated three-mirror cavity [6] ion laser [I] asa possible simple and efficient pumpsource. at the position of the cavity focus (see Fig. 1.) A low dye flow of Recently, Johnston and Runge mentioned the use of a pulsed thevelocity onthe order ofa few millimetersper second is xenon laser for pumping dyes [2].We report on a xenon laser- sufficient for maintaining laser oscillation. Speeding up the flow pumped , which is inexpensive, easy to set up, and ex- does not increase the power output. The dichroic plane mirror1 hibits certain favorable output characteristics,including a repeti- is highly reflective in thespectral region X > 560nm, but tion rate of120 pulses per second (pps)and a pulse lengthof up to transparent in the green andadmitting passageof thelight. 300 ~s,which is longcompared withpulses of other laser- Mirror 2 (R = 5 cm) is highly reflective overa broad band, pumped dye . whereas mirror 3 (R = IO cm) has 4 percent transmission in the A pulsed xenon laser as used in our experiments can be built yellow and red and high transmission for X < 520 nm. Conse- with very moderate effort. The discharge tube, equipped with quently, only the green xenon laserlight-or less than half of the Brewster windows, has an active length of 120 cm and a bore total power-is used to pump thedye when thesemirrors areused. diameter of 4 mm. Two halves of an old flashlamp, partly filled Two output beams aretransmitted through mirror 3 and are withindium metal [3], serveas cold electrodes. Thetube is monitored with a fast ITT planar photodiode and a Tektronix operated at 5-20 mtorr xenon pressure [4] by a 20-kV 60-H~ model 5 19 oscilloscope. neon sign transformer and an8- or 12-nF barium titanate “door- Two different dye liquidshave been used successfully. A5. knob” capacitor bank in parallel with the discharge tube. The M/I solution of rhodamine 6G in water +5 percent ammonyx discharge fires twicein each k-s period, and at optimumpressure, LO and a solution of 85-mg purified cresyl violet [7] in 350 ml the sequence of pulsescan be stable overperiods of several ethanol. The characteristics of the dye laser output are given in minuteseven though no specialtrigger device is used.Oc- Table I. The single-pass gain of the dyes was estimated by inser- casionally, a single pulse is skipped. The xenon laser cavity con- ting a thin fused silica slide into the dye laser resonator and sists of two plane mirrors, oneof which is highly reflective over a tilting it until threshold is reached. With rhodamine 6G, it was broad band, whereas the other one has a transmission of about possible to couple out more thantwice as much power by reflec- tion from this slide than by transmission through mirror 3. The Manuscript received December 26, 1972; revisedJanuary 19, 1973. This work was possible increase in output power forcresyl violet with optimum partly supported by the National Science Foundation under Grant GP-28415. outcoupling seems to be smaller. With fluorescein diacetate as T. W. HInsch and A. L. Schawlow are with the Departmentof Physics, Stanford thedye medium, oscillation slightly abovethreshold was ob- University, Stanford, Calif. 94305. tained. P. Toschek is with the Department of Physics, Stanford. University, Stanford, Calif., on leave from the Institute of Applied Physics, University of Heidelberg, Thisdye laser system offers someattractive features. The Heidelberg, Germany. pulse-repetition rate is comparable to that of a 554 IEEE JOURNAL OF QUANTUM ELECTRONICS, MAY 1973 pumpeddye laser. The pulse length is 10-20 times longer, REFERENCES however, and the pump source is 1-2 orders of magnitude less expensive. This latter convenience also holdsin comparison with [I] W. B. Bridges. “Laser action in single ionized and xenon.” /’roc. /LE/; (Corresp.). vol. 52. pp. 843-844. July 1964. a frequency-doubled Nd:YAG laser. Our device compares 171 W. I>. Johnston. Jr.. and P. K. Runge. “An improved astigmatically compen- favorably also to CW dye lasers pumped by an ion laser, sated resonator forCW dye lasers,”IEEE J. Quantum Electron. (Corresp.), vol. since it has higher peak power and the capabilityof using a wider QE-8, pp. 724-725, Aug. 1972. varietyof dyes andthereby covering greatera range of (31 W. W. Simmons and R. S. Witte. “New cold cathode for pulsed ion lasers,“ IEEE J. Quantum Electron.(Corresp.), vol. QE-6, pp. 648-649. Oct. 1970. wavelengths. The simple pump laser even emits on lines in the 141 V. Hoffmann and P. Toschek. “New laser emission trom ioniTed xenon,” /EEf blue and UV spectral range, which can be favored by a properly J. Quumuw Elwtro~t.(Notes and Lines), vol. QE-6, p. 757. Now 1970. chosen set of mirrors, and might be utilized for the optical pump- [5] V. HolTmnnn ;ind P. Toschek. “New Emissionslinien im Xenon-Ionenlaser,” Lxer Kep. 3-70. Inst. Angewandte Phys. Univ. Heidclbcrg. Heidelberg. Ger- ing of dyes. The largegain should permit the in,sertionof mony. 1970. relatively lossy tuning elements into the dye laser cavity [8], and [h] H. W. Kogelnik, E. P. Ippen, A. Dienes. and C. V. Shank, “Astlgmatically thecomparatively long pulses may be useful, when extremely cwnpensated cavities for CW dye lasers.” IE‘EEJ QuwrwtI /./wtrou., voI. Q€:- narrow-band laser radiation is to be generated, because the dis- X. pp. 373-379. Mar. 1972. persive intracavity elements experience more light passes with [7] Gacoin and P. Flamant, “High efficiency cresyl violet laser.” Opt. C‘onlrnun.. vol. 5. pp. 351-353. 1972. long light pulses, and because the Fourier transform bandwidth [X] T. W. Hiinsch. “Repetitively pulsed tunable dye her for high rerolution spec- limit for a 0.3-ps light pulse of Gaussian shape is only 1.5 MHz. troscopy,“ .Ippi Opr.. vol. 11. pp. X95-898. Apr. 1972.

Contributors

V. A. Batanov was born in Moscow, USSR, on Aviv University. His recent research interests have included vibrational October 27,1943. Hegraduated from the and rotational relaxation in the gas phase and gas and chemical lasers. MoscowPhysical Technical Institute, Moscow, in 1966, and did post graduate work at the same institutefrom 1966 to 1968. Since 1967 hehas been scientista at the LaboratoryofOscillations, P. N. Lebedev .:. Institute,Academy of Sciences,Moscow. His main interest is experimental investigations of in- tense metal evaporation under a laser beam. Richard A. C‘hodzko was born in Whittier, Calif.. on January 12. 1939. He received the R.A. dcgree r:. in physics xt theUniversity ofCalifornia. Berkeley,and the Ph.D. degree in engineering phyTics atthe University of California. Snn F. V. Bunkin wasborn in Moscow, USSR, on Diego, in 1962 and 1970. respectively. January 17, 1929. Hegraduated from the From 1962 to 196.5 he worked for the Lockheed PhysicalTechnical Faculty of MoscowState Propulsion Company in an advancedplanning University,Moscow, in1952, andwas a post group on propulsion system design. Since 1971 he graduateat the P. N. LebedevInstitute, has been ;i member of the Technical Star of the Academyof Sciences, Moscow, from 1952 to Aerospace Corporation, Los Angeles, Calif. His 1955. He received his first degree in physics for fields of activityinclude laser interactions in absorbinggases and op- the theory of thermal emission from anisotropic tic11 cavity design for continuous chemical lasers. mediain 1955, andthe second degree for the Dr. Chodzko is a member of the American Institute for Aeronautics resultsofinvestigation on fluctuation in and Astron:tutics. equilibriumand nonequilibrium physical systems in1963. At present he heads a division of the Laboratory of Oscillations at the Lebedev Institute, where heis studying the interaction of powerful optical .:. radiation with substance.

ltamarBurak received the M.S. ar,dPh.D. degrees in chemistry from the Hebrew University ofJerusalem, Jerusalem, Israel, in 1961 and 1965, respectively. From 1965 to 1967he was Instructor in the Department of Chemistry, Tel-Aviv University. Tel-Aviv,Israel. From 1967 to 1970he wits ResearchAssociate in theDepartment of Chemistry,Massachusetts Institute of Technology, Cambridge. Recently, he has joined the faculty of the Department of Chemistry. Tel-