Rare Gas Halide Lasers Research Articles

Discharge stability of electrically excited rare-gas halide laser systems

An explanation of the cause of discharge constriction in an electrically excited XeCl* laser system is presented. Our analysis, carried out for a specific system, is more generally applicable to other rare-gas halide lasers and represents a contribution to the theory of discharge stability in high-pressure, strongly electron-attaching gas mixture. The conclusions obtained in various theories of the growth of instabilities in high-pressure laser discharges, thus far appeared in the literature, are briefly resumed and compared with our experimental and theoretical findings. Finally, prospects for obtaining a better discharge stability in rare-gas halide systems are discussed.

Time-resolved measurements of emission and absorption in a long pulse duration XeCl* laser

In this paper we describe time-resolved absorption and emission studies of an XeCl* laser discharge. The studies we carried out in order to gain a better understanding of the causes leading to the premature termination of both spontaneous emission and laser pulses in our device. This is a feature showed by all discharge pumped rare gas halide lasers.

Analysis of temporal-length limitations in XeCl lasers

Experimental observations of the development of constrictions in rare-gas halide laser discharges are reported. The onset of constriction is related to the premature termination of both spontaneous emission and laser pulses in a discharge-excited XeCl laser. A mechanism is proposed to account for the onset of constriction in this laser which may be more generally applicable to other discharge-excited devices.

Resonant transformer command charging system for high repetition rate rare-gas halide lasers

A resonant transformer pulse generator for the pumping of high repetition rate rare-gas halide discharge lasers is described. Since with this design a low-voltage dc power supply is needed, command charging can easily be achieved by using a thyristor as the switching element. The pulse generator has been tested driving a thyratron-switched laser operating up to 100 pps free running and up to 200 pps in the burst mode.

Wide aperture self-sustained discharge KrF and XeCl lasers

A UV-preionized rare-gas halide laser with a large aperture to 7×7 cm2 and active volume of 4 ℓ has been operated at a high pressure regime of 5 atm. Beam profile measurements at the midplane between electrodes have shown the beam widths of 7 cm at a half-energy density both in KrF and XeCl. The improvement in discharge homogeneity and extension of the optical pulse duration have been obtained by the peaking of the discharge current with a small stray capacitance between the rail gap and the laser head as well as by the use of Ne rather than He as a buffer gas, resulting in the output energy of 13.8 J in XeCl and 5.0 J in KrF.

Analysis of chemical degradation products in an e-beam pumped rare-gas halide laser

Chemical degradation products created during the operation of an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</tex> -beam pumped, repetitively pulsed XeF laser with closed flow cycle capability are reported. From an initial lasing mixture of Ar/Xe/NF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> , the degraded gas was found to contain N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> (N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> ), CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , nitrogen oxides, CF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> , and SiF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> . Gaseous species were identified by their infrared and ultraviolet absorption spectra. Also present was a solid material tentatively thought to consist of fluorocarbons and aluminum fluorides. The observed gas chemistry suggests methods for improving laser performance by prevention of contaminant buildup.

Gain-dependent dispersion in a XeF laser

In high-power rare-gas halide lasers the effects of gain-dependent optical dispersion may be sufficiently large to affect output-beam quality. We used a semiclassical approach to study this problem. The results for the case of a XeF laser are presented.

Compact, simple, high-energy, discharge-pumped rare gas halide laser

A simple, lumped capacitor, avalanche discharge excimer laser has been developed which uses a single spark array preionization rod located under a grid electrode to preionize the discharge region. A surface corona discharge is found to play an important role in achieving a more uniform transverse preionization. On KrF, energy in excess of 0.5 J is obtained (≳2.4 J/1) with a wide (16 × 25 mm) uniform beam of good divergence (1.8 × 5 mrad) and electrical efficiency above 1%.

Photocyclization of carvone to carvone camphor using rare gas halide lasers

The intramolecular photocyclization of (-)carvone with rare gas halide lasers is decribed. A 70-fold increase in quantum yield is observed at an intensity of 60 MW/cm 2, which is rationalized in terms of consecutive two-photon absorption. The mechanism proposed also describes the product distribution, which is different from that obtained by lamp irradiation.

A simple technique for measuring the gain of RGH lasers

Describes a simple experimental technique which allows the gain of a rare gas halide (RGH) laser discharge to be estimated rapidly and reliably. The gain of the discharge is offset by including in the laser cavity a cell containing a passive absorber gas. The absorbance of the gas which just extinguishes laser action is related in a simple way to the gain of the discharge.

Subnanosecond pulse amplification in rare gas halide lasers

Subnanosecond pulse amplification in rare gas halide lasers

Rare gas recovery systems for rare gas halide lasers

A system is described for the recovery of xenon from XeCl lasers and variants for other rare gas halide (RGH) combinations are presented. The batch recovery systems discussed are simple and cost effective and lead to no degradation of laser performance. The added cost associated with continuous gas processing seems difficult to justify at the present time for a system of this size.

Axisymmetric angular encoder for laser fusion

We report the demonstration of an angular encoder which produces a discrete conical scan of 25 pulses, each 10 ns in duration. The device is a key optical subsystem for efficient generation of short optical pulses from laser media with short energy storage times. In particular, an encoder of this type may be necessary for use of the rare gas halide laser media in fusion experiments. Our device was also operated as a ring resonator with internal imaging and image rotation. Potential uses, aside from laser fusion, include laser scanning systems and resonator designs in which image rotation is desirable.

Frequency mixing in the extreme ultraviolet

The generation of coherent XUV radiation through harmonic generation and frequency mixing is described. Results that have been obtained using third- to ninth-order nonlinear interactions are summarized. The use of rare gas halide lasers for generating tunable XUV radiation is discussed.

Photoionization of excited rare-gas atoms

Cross sections have been calculated for photoionization of the first excited $s$, $p$, and $d$ states of the heavier rare gases (neon, argon, krypton, and xenon). A semiempirical, central-field approximation has been used in which an effective core polarizability was adjusted to fit the computed eigenvalues to the known excited-state binding energies for each atom. The calculations have revealed interesting features in many of the cross sections, and these are described and analyzed. In addition, the role of excited-state photoionization processes in short-pulse raregas-halide lasers is briefly discussed.

A triatomic Xe2Cl excimer laser in the visible

A new triatomic rare-gas halide laser using the molecular exciplex Xe2Cl is described. Laser emission centered at 518 nm with a special bandwidth of 30 nm and peak power of about 2 kW was obtained from an electron-beam-excited high-density Ar/Xe/CCl4 mixture.

Gas composition and lifetime studies of discharge excited rare-gas halide lasers

A spectroscopic study has been made of the stable species produced in rare-gas halide laser discharges. Molecules observed to be created in rare-gas fluoride discharges were NO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , SiF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> , CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , ClO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> CO, FNO, FNO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , and NF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> of which only NO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , and ClO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , in the case of XeF, appreciably absorb at the laser wavelengths. These latter species were created from the air impurities in the F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and He gases and their creation acts to deplete the F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> donor. For ArF, the lifetime of the gas could be considerably extended by circulating the gas through a liquid N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> trap. For the rare-gas chlorides, no discharge induced species were spectroscopically detected although AlCl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> powder was formed in the laser tube. A more F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> compatible laser tube than glass and high purity F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> should be used for long lived rare-gas fluoride operation.

Operating characteristics of a closed cycle flow rare gas halide laser

A UV preionized, high-purity construction, closed-cycle-flow rare-gas-halide laser has been constructed to study laser characteristics at high pulse repetition frequency and closed cycle behavior of the laser chemistry. Operating characteristics of the laser with ArF, KrF, XeF, and XeCl have been obtained. The XeCl laser has demonstrated the best performance, yielding a maximum average power of 45 W at 600 Hz and greater than 35 W at 500 Hz for 1 h.

Rare-gas halide avalanche discharge lasers

This paper summarizes a series of studies aimed at understanding rare-gas halide lasers excited by UV preionized avalanche discharges. Discussions include steady-state rate equation calculations of the kinetics, parametric variations and optimizations of discharge characteristics, and gas mixture optimizations for high-energy lasing.

Negative ion production rates in rare gas-halide lasers

This paper reports on dissociative electron attachment in F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , NF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> , Cl <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , and I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . The principle of the method is to produce a short burst of photoelectrons from a photocathode by means of light from an argon-fluoride laser. Subsequently, by studying the motion of electrons and negative ions in a constant electric field ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> ) region, information is obtained about drift velocities and effective attachment cross sections. Helium, argon, and nitrogen were used as buffer gases. Of particular interest is a very strong temperature dependence of the attachment coefficient in I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . Measurements were taken from 35 to 110°C, covering an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E/N</tex> range of 1-50 Townsend. An explanation based on vibrational excitation is presented.