Contains reports on three research projects.U.S. Air Force - Office of Scientific Research (Contract F49620-79-C-0071)Joint Services Electronics Program (Contract DAAG29-80-C-0104)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0694

Salour, Michael M.

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Quantum Optics and Electronics11. Quantum Optics and ElectronicsAcademic and Research StaffProf. M.M. Salour, Dr. G.W. Fehrenbach, Dr. A. Fuchs, Dr. P. Jaanimagi,Dr. P.H. Kayoun, Dr. P. Kumar, Dr. R. Welte, F. W. BarrowsGraduate StudentsN.S. Bergano, R.S. Bondurant, M. Maeda, R.S. Putnam, J. Yorsz11.1 Nonlinear Optical Interactions in SemiconductorsU.S. Air Force - Office of Scientific Research (Contract F49620-79-C-0071)Michael M. SalourThe aim of this program is to investigate a variety of novel, nonlinear optical interactions thataccompany, or immediately follow, the creation of an electron-hole pair in semiconductors. We havepreviously reported tunable cw laser action with platelet semiconductors in both mode-locked andunmode-locked configuration using CdS, CdSe, and CdSSe. These optically pumped semiconductorplatelet lasers do not require complicated heterostructures and thus may be easily changed todifferent wavelength regimes by varying the sample composition. With a potentially continuoustuning range between 500 nm and 1.5 /m they may become useful tools for spectroscopy in both thetime and frequency domains.More recently we have achieved the first optically pumped, mode-locked semiconductor laseroperating at wavelengths longer than 1.0 pFm. Laser operation was achieved in two separatecompostions of In1xGaxAsyP 1y at 1.1 and 1.2 jpm with x = .20, y = .4 and x = .24, y = .55,respectively. Pulses as short as 7 ps were obtained with tunability over a range of 26 nm. Cwoperation was also achieved with a reduced duty cycle to compensate for the comparatively poorthermal conductivity of the quaternary layer.In collaboration with Dr. T.C. Harman of Lincoln Laboratory we have also operated the first opticallypumped HgCdTe laser in an external cavity. The laser operates in the range of 1.2tp - 2 Ip withsamples prepared by liquid phase epitaxy on CdTeSe substrates. We have achieved a peak outputpower of 50 watts when mode-locked with an average output power of as much as 5.6 MW. Outputspulses as short as 5.3 psec were measured with a time-bandwidth product of 0.55. Unmode-lockedoperation, and operation at temperatures above 100 K were also demonstrated.During the past year we have also demonstrated platelet semiconductor lasing for the first time in aring resonator. Low threshold has been achieved with bidirectional operation of the ring but strongRLE P.R. 125Quantum Optics and Electronicscoupling effects have thus far prevented unidirectional operation.11.2 Picosecond Dye Laser OpticsJoint Services Electronics Program (Contract DAAG29-80-C-0104)U.S. Air Force - Office of Scientific Research (Contract F49620-79-C-0071)Michael M. SalourOur picosecond dye laser system has been extended to high power operation by the addition offour dye amplifier stages. A frequency-doubled, Q-switched Nd:YAG laser pumps the dye amplifiersin synchronism with a pulse from the train of a synchronously-mode-locked dye oscillator. A pulsefrom the oscillator is then amplified to peak powers of several gigawatts (for pulse duration of severalpicoseconds at a repetition rate of 10 Hz). An electron-optic streak camera, interfaced to amultichannel analyzer and minicomputer, has been adapted for use at the 10 Hz repetition rate.For the system's initial demonstration we have performed time resolved laser induced fluorescencespectroscopy of the hydroxyl radical in flame. The results reported extend previous measurements ofOH211(v' = 0) quenching rates in subatmospheric pressure flames to atmospheric pressures. Theapplication of this technique to even higher pressure flames appears feasible. The collisionalquenching lifetime following excitation of the R2(4) 2H(v' =0)<---2 +(v' ' =0) transition wasmeasured to be 1.8 ns in the burned gas region of an atmospheric pressure, premixed methane-airflame.We have also reported the first experimental technique for compensating the pulse broadening insingle-mode optical fibers, using the "slow" anomalous pulse propagation in the exciton-polaritonresonance in a direct-gap semiconductor. Mode-locked dye laser pulses of 0.7-ps duration at 8180 Awere propagated through a 100-m single-mode optical fiber and emerged with 2.8-ps duration. Wehave demonstrated the compensation of this pulse broadening in optical fibers by passage through a6.3 - nm-thick GaAs crystal, taking advantage of the group velocity dispersion around the discreten = 1 exciton-polariton resonance.1 1.3 Nonlinear Spectroscopy of Atoms and MoleculesU.S. Navy - Office of Naval Research (Contract N00014-79-C-0694)Michael M. SalourA series of novel experiments has been initiated to study the photon statistics of light produced bydegenerate 4-wave mixing (DFWM). The goal of this work is the generation of light in two-photoncoherent stages.RLE P.R. 125Quantum Optics and ElectronicsConsiderable advance has been made in achieving the laser stability required for the observation ofnon-classical statistics. Output from a frequency-stable ring dye laser is amplified in a 3-stage dyeamplifier pumped by a frequency-doubled 0-switched Nd:YAG laser. Use of a novel pulse shapingnetwork has resulted in the generation of nearly transform-limited pulses of 4 nsec duration. DFWMhas been observed in Na vapor. So far, photon counting measurements made both on reflected andtransmitted probe beams have yielded Poisson statistics. High loss and background fluorescencehas restricted these measurements to the regime of classical statistics. Several alternative schemesare being pursued.RLE P.R. 125RLE P.R. No. 125 58

Quantum Optics and Electronics

Quantum Optics and Electronics10. Quantum Optics and ElectronicsAcademic and Research StaffProf. M.M. Salour, Dr. G.W. Fehrenbach, Dr. A. Fuchs,Dr. P. Jaanimagi, Dr. H.P. Kayoun, Dr. P. Kumar,Dr. F.P. Leland, Dr. R. Welte, Dr. T.K. Yee,F. W. BarrowsGraduate StudentsN.S. Bergano, R.S. Bondurant, J.G. Fujimoto,B.C. Johnson, M. Maeda, G.W. Miller, R.S Putnam,C.B. Roxlo, J. Yorsz10.1 Nonlinear Optical Interactions in SemiconductorsU.S. Air Force - Office of Scientific Research (Contract F49620-79-C-0071)Michael M. SalourThe aim of this program is to investigate a variety of novel, nonlinear optical interactions thataccompany, or immediately follow, the creation of an electron-hole pair in semiconductors. Thesestudies will combine theory and experiments on the basic physics of the interaction of intensepicosecond pulses with semiconductor systems involving mobile carriers.We have demonstrated tunable cw laser action of platelet semiconductors in both mode-lockedand unmode-locked configurations. The gain media were platelets of CdS, CdSe, CdSSe, andInGaAsP, cooled to 850 K and longitudinally pumped by Ar and Kr' lasers. Antireflection coating ofthe crystal face and external bandwidth restriction have been used to generate pulses as short as 4 psin CdS. The pulses observed are chirped, with nontransform-limited time-bandwidth products ofabout 1.7. The energy conversion efficiency is 20% into the TEMoO mode, with output powers of over10 mW from CdS. Pulses as short as 7 ps tunable over a 26-nm range have been obtained in InGaAsP.These compounds can potentially provide continuous tunability between 500 nm and 1.5 tpm, arange which is not entirely available from dye lasers. Because of the lack of dye jet fluctuations,semiconductor lasers may provide narrower linewidths than dye lasers, and samples mountedadjacent to each other can be easily changed to provide tunability over a broad range. A very longshelf life and the lack of orientational bleaching may make these lasers more practical than F-centersfor many applications. Optically pumped semiconductors should provide a useful tool forspectroscopy in both the time and frequency domains.RLE P.R. No. 124Quantum Optics and Electronics10.2 Picosecond Dye Laser OpticsJoint Services Electronics Program (Contract DAAG29-80-C-0104)U.S. Air Force - Office of Scientific Research (Contract F49620-79-C-0071)Michael M.SalourWe have observed photoelectric emission and thermally enhanced photoelectric emission from azirconium metal surface using our intense UV laser pulses of two-picosecond durations. Our datashow that the electron and lattice-temperature remain approximately equal, and the electron-phononenergy relaxation time is less than one picosecond.In another series of experiments we have made detailed measurements of the luminescent spectraof CuCI as a function of pump power and temperature.Excellent agreement was found with earlier values for exciton energy; however, a new broadbackground was found at high excitation. Evidence for free Cu in the luminescence spectra is foundin all samples under very high excitation, even in the samples which had been carefully screened forfree Cu by x ray and ESR. We have observed a broadening of the Z3 line, which we tentatively ascribeto phonon effects due to the modified "Cu", CuCI structure.Finally, we have observed the time dependence of the bound luminescence of the CuCI by excitingsingle crystals of CuCI at 80K with the low-intensity frequency-doubled output of an actively mode-locked R6-G dye laser. We have measured the time dependence of the bound exciton luminescencedirectly by a synchronously operating electron-optical streak camera accumulating data at the dyelaser repetition rate of 82 MHz. We have determined (directly) that the observed bound excitonlifetime for the I line (3898 A) is typically -130 ps with a formation time of less than 10 ps.10.3 Nonlinear Spectroscopy of Atoms and MoleculesU.S. Navy - Office of Naval Research (Contract N00014-79-C-0694)Michael M. SalourWe have demonstrated a new method of "light-by-light switching" in a unidirectionally amplifyingmedium, based on the method of Doppler compensation by velocity-dependent light shifts. The timeresponse of such a switch is limited by the fact that the bandwidth of the compensating pulse has tobe small compared to the Doppler width of the atomic vapor. These widths are generally of the orderof gigahertz, which means that the response time cannot be shorter than a few nanoseconds (i.e.,-10-9 sec). The rise and fall times of the switching are determined by the rise and fall times of thesuperfluorescent pulse which, in this experiment, was of the order of one nanosecond (i.e., 10- 9 sec).RLE P.R. No. 124Quantum Optics and ElectronicsA very e'xciting feature of this switching technique is its unidirectionality, which makes it a unique toolfor applications in optical communications, ring lasers, Doppler-free directed superradiance, Doppler-free coherent transients, and so on.PublicationsMiller, D.E., "Microprocessor Controlled Passive Area Navigation System for Light Aircraft," S.B.Thesis, Department of Electrical Engineering and Computer Science. M.I.T., June 1978.Rotman, S.R., C.B. Roxlo, D. Bebelaar, and M.M. Salour, "Pulsewidth Stabilization of a SynchronouslyPumped Mode-Locked Dye Laser," Appl. Phys. Lett. 36, 886 (1980).Petite, G., B.C. Johnson, W.K.H. Lange, and M.M. Salour, "Observation of Unidirectional AmplifiedSpontaneous Emission induced by Velocity Dependent Light Shifts," Phys. Rev. Lett. 45, 1242(1980).Heinrichs, R.M., "Efficient Conversion of XeF Radiation to the Blue-Green through Stimulated RamanScattering," S.M. Thesis, Department of Electrical Engineering and Computer Science, M.I.T.,June 1980.Messinger, B.J., "Angular Distribution of Electrically Scattered Light from Cylindrical Glass Fiber,"S.B. Thesis, Department of Electrical Engineering and Computer Science, M.I.T., June 1980.Rotman, S.R., "Active Feedback Stabilization of Ultrashort Pulses in a Synchronously Mode-LockedDye Laser," S.M. Thesis, Department of Electrical Engineering and Computer Science, M.I.T.,June 1980.Rotman, S.R., C.B. Roxlo, D. Bebelaar, and M.M. Salour, "Pulsewidth Stabilization of a SynchronouslyPumped Dye Laser," Proc. of the Picosecond Phenomena Conference, North Falmouth, MA,July 18-20, 1980.Roxlo, C.B. , D. Bebelaar, and M.M. Salour, "Tunable CW Bulk Semiconductor Platelet Laser," Appl.Phys. Lett. 38, 507 (1981).Roxlo, C.B., and M.M. Salour, "Synchronously Pumped Mode-Locked CdS Platelet Laser," Appl.Phys. Lett. 38, 738 (1981).Fujimoto, J.G., T.K. Yee, and M.M. Salour, "Picosecond Spectroscopy of Bound Excitons in CuCIUsing a Synchronously Operating Streak Camera," Appl.Phys. Lett. 39, 12 (1981).Johnson, B.C., G. Petite, W.K.H. Lange, and M.M. Salour, "Observation of Unidirectional AmplifiedSpontaneous Emission Induced by Velocity Dependent Light Shifts," Bull. Am. Phys. Soc. 26,57 (1981).Fujimoto, J.G., T.K. Yee, and M.M. Salour, "Measurement of Low Intensity Bound ExcitonLuminescence of CuCI Using a Synchronously Operating Streak Camera," presented at theInternational Conference on Excited States and Multiresonant Nonlinear Optical Processes inSolids, Aussois, France, March 18-20, 1981.Fujimoto, J.G., "Direct Determination of Excitonic Lifetime in CuCI Using a Picosecond SynchroscanStreak Camera," S.M. Thesis, Department of Electrical Engineering and Computer Science,M.I.T., June 1981.Johnson, B.C., "Unidirectional Amplified Spontaneous Emission through Doppler Compensation,"S.M. Thesis, Department of Electrical Engineering and Computer Science, M.I.T., June 1981.Fujimoto, J.G., T.K. Yee, and M.M. Salour, Paper WR2: "Application of a Synchronously OperatingStreak Camera to the Measurement of Bound Exciton Luminescence in CuCI," presented atthe Conference on Lasers and Electro-optics (CLEO '81), Washington, D.C., June 10-12, 1981.Roxlo, C.B., and M.M.Salour, Paper WR4: "Generation of Picosecond Pulses from a SynchronouslyPumped CdS Platelet Laser," presented at the Conference on Lasers and Electro-optics(CLEO'81), Washington, D.C., June 10-12, 1981.Salour, M.M., "Optically Pumped Semiconductor Platelet Lasers," presented at the Fifth InternationalConference on Laser Spectroscopy, Jasper Park, Canada, June 29-July 3, 1981.RLE P.R. No. 124Quantum Optics and ElectronicsSalour, M.M. and G. Petite, "Light-Induced Unidirectional Light Switching. presented at the FifthInternational Conference on Laser Spectroscopy, Jasper Park, Canada, June 29-July 3, 1981.Petite, G., B.C. Johnson, W.K.H. Lange, and M.M. Salour, "Observation of Unidirectional GainInduced by Velocity Dependent Light Shifts," Proc. of the 7th International Conference onAtomic Physics, Boston, MA, August 4-8, 1981.Roxlo. C.B.. "Optically Pumped Synchronously Mode-Locked Semiconductor," PhD. Thesis,Department of Electrical Engineering and Computer Science, M.I.T., September 1981.Salour, M.M., and G. Petite, "Light Induced Unidirectional Light Switching," Opt. Lett., to appearDecember 1981.Roxio, C.B., R.S. Putnam, and M.M. Salour, "Optically Pumped Semiconductor Platelet Lasers," IEEEJ. Quantum Electron., to appear March 1982.Roxlo, C.B. and M.M. Salour, "Dewar Design for Optically Pumped Semiconductor Lasers," to appearin Rev. Sci. Instrum.Lefkowitz, I., T.K. Yee, J.G. Fujimoto, M.M. Salour, and M. Combescot, "Evidence for New Features inthe Luminescent Spectra in CuCI," submitted to Phys. Rev. Lett., 1981.RLE P.R. No. 124

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