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Verdeyen, J. T.

Publications and source records attributed to Verdeyen, J. T..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Broad-band gain in optically pumped S2

The broad fluorescence spectrum and Franck-Condon shift of the B-X system of S2 are exploited in broad-band-gain experiments using the absorption of 308-nm XeCl excimer radiation to pump the level (upsilon-prime = 4) in an S2 vapor with and without Ar. The fluorescence spectra are examined to determine the effects of gas collisions, and the intense near-UV and visible bands are attributed to the redistribution of the population among the upsilon-prime levels resulting from S2-Ar collisions. Broad-band gain is observed on the rare-gas relaxation bands (2,17) (about 475 nm) and (3,18) (480 nm), while absorption is found in the (0,6), (0,7), and (0,8) near-UV (about 360-380-nm) bands where a transient population cascading down the X-state manifold fills the lower levels. It is inferred from the achievement of gain over much of the S2 fluorescence bandwidth that nonselective pumping mechanisms like discharges, solar energy, or flashlamps can be used with S2 as the tunable, chemically stable 'dye'.

Epler, J. E.↗
NASA NTRS1983

Low temperature operation of an S2 laser using radio frequency simmer discharges

Technological problems stemming from high temperature operation of the sulfur resonator have hindered its development as a tunable, efficient, discharge pumped laser. The use of RF simmer discharges is shown to reduce previous temperature constraints by dissociating polyatomic sulfur molecules into the dimer, such that lasing is achieved when pumped by an XeCl excimer laser. The peak power output of the S2 laser and the transmission spectra through sulfur discharges are used to infer the effectiveness of the discharge in dissociating the vapor.

Killeen, K. P.↗
NASA NTRS1982

Electric discharge effects on a XeCl pumped S2 heat-pipe laser

It is shown that an electrical discharge can dissociate the higher-order sulfur molecules S(3-8) into dimers S2 and thus create the proper environment for efficient conversion of XeCl radiation at 308 nm to the blue-green. The use of a heat-pipe configuration greatly alleviates the technological problems.

Killeen, K.↗
NASA NTRS1981

I/asterisk/ /6s 4P/ collisional quenching - Application to the IF 491-nm laser

Measurements of the rate constants for quenching of the excited I (6s 4P) states by Ar, Xe, CF39I, UF6, and NF3 are described. Each rate constant is determined by recording the exponential time decay of the excited IF or excited I2 (342 nm) fluorescence in the afterglow of the e-beam-excited plasmas containing Ar, CF3I, NF3, and the desired quenching gas. In addition, further experimental evidence in support of neutral channel formation of excited IF in e-beam-pumped Ar/CF3I/NF3 mixtures is presented. Details of the experimental apparatus and gas handling procedures are given, and the kinetics model developed to interpret the experimental data is described.

Hutchison, S. B.↗
NASA NTRS1981

Iodine monofluoride 140-kW laser - Small signal gain and operating parameters

Output energies in excess of 4 mJ in a 30-nsec FWHM pulse (140-kW peak power) have been obtained from a discharge-pumped IF laser for a cavity output coupling of 35%. In addition, oscillation on a new transition of the IF (E-A) band at 472.7 nm has been observed. By measurement of the output power of the laser for various values of output mirror transmission, the small signal gain and loss coefficients were found to be (3.1 + or - 0.7)%/cm and 0.3%/cm, respectively.

Dlabal, M. L.↗
NASA NTRS1980

Iodine monofluoride emission spectrum and formation kinetics in electron-beam-produced plasmas

The observation of intense blue-green spontaneous emission attributed to IF from electron-beam-excited Ar/CF3I/NF3 gas mixtures is reported. Intense emission from a structured band centered at a wavelength of 484 nm was observed when mixtures of 2000-4000 Torr AR (or He or Ne), 3 Torr CF3I and 1 Torr NF3 (or F2) were irradiated with a 3-nsec FWHM electron beam. Analysis of ICl and IBr spectra, which the present spectrum closely resembles, indicates that the 484-nm emission originates from the E to A 3 pi 1 transition of IF. Examination of the time dependence of metastable IF and I2 emission reveals that the IF (E) level is formed primarily by excitation transfer from metastable I(4P) states. The fluorescence efficiency of the E-A transition and the radiative lifetime of the metastable IF (E) state are estimated to be approximately 6% and 15 nsec, respectively, and it is suggested that metastable IF is an attractive candidate for a blue-green laser.

Hutchison, S. B.↗
NASA NTRS1980

Lasing characteristics of gas mixtures involving UFG: Application to nuclear pumping of lasers

Intense blue-green fluorescence from a structured band centered at lambda approximately 484 nm was observed from Ar, CF3I and NF3 gas mixtures excited by an electron beam. This emission was tentatively assigned to the E yields A transition of the iodine monofluoride (IF) molecule. The fluorescence efficiency of the IF(E yields A) band and the IF (E) state radiative lifetime were estimated to be approximately 6% and 15 ns, respectively. The emission band structure, the short IF(E) radiative lifetime and the Franck-Condon shift between the E and A states suggest that IF is an attractive candidate for a blue-green laser.

Verdeyen, J. T.↗
NASA NTRS1980

The hollow-cathode helium-fluorine laser

It is possible to obtain uniform stable long-pulse excitation (in excess of 100 microsec) in gas mixtures involving highly electronegative constituents (SF6, CCl4, NF3, and I2). Such a system was used to investigate the atomic fluorine laser. In the hollow cathode, lasing on fluorine transitions in the doublet system lasted for up to 80 microsec with no signs of the self-termination as reported previously in positive-column devices. The excitation process of the laser appears to depend heavily upon the fluorine donor utilized. For instance, a single-step process is involved when NF3 is used whereas a two-step process is evident for SF6. The details are discussed.

Crane, J. K.↗
NASA NTRS1979

Studies of basic mechanisms occurring in high pressure gases: Applications to high efficiency high power lasers

The atomic fluorine laser was investigated. In the hollow cathode, lasing on Fluorine transitions in the doublet system lasted for up to 80 microns with no signs of self-termination. The excitation process of the laser appears to depend heavily upon the fluorine donor utilized. For instance, a single step process is involved when NF3 is used whereas a two step process is evident for SF6. The details are discussed.

Crane, J. K., III↗
NASA NTRS1976

The pumping mechanism for the neon-nitrogen nuclear excited laser

In order to determine the physical processes for pumping this laser, a detailed study of the afterglow system has been performed. The pumping mechanism has been found to be collisional-radiative electron-ion recombination. Microwave quenching of both the laser and spontaneous afterglow light have shown conclusively that a recombination process directly produces a nitrogen atom in either the upper laser level or, more likely, in a higher lying energy level which rapidly de-excites to the upper laser level.

Cooper, G. W.↗
NASA NTRS1975

Studies of discharge mechanisms in high pressure gases-applications to high efficiency high power lasers

By measuring the absorption and emission cantinua of various states in the cesium/xenon molecule, the collisional rates critical in populating the alkali/rare gas excimer levels have been estimated. Cs atomic states that are weakly optically connected to ground have been shown to form excimer levels that are attractive as potential dissociation lasers. In particular, the (Cs/7 2S/Xe) excited molecule appears promising as a source of high energy laser radiation due to its large dissociation energy, stimulated emission cross section, and small population inversion densities. Monitoring of the optically pumped Cs2 molecular absorption profile in the presence of xenon shows a drastic change with increasing xenon pressure for the Cs2C band. Dominant absorption at large xenon densities is centered around approximately 6380 A as opposed to 6300 A for lower perturber pressure.

Cherrington, B. E.↗