Compact,wide aperture X-ray preionized XeCl laser with high specific optical power

An X-ray preionized, discharge-pumped XeCl laser with a variable beam cross-section of up to 6×6 cm² is described. It uses flat electrodes and the beam width is determined by X-ray collimation. Its operation characteristics concerning reduced electric field strength (E/p) and X-ray dose are discussed in detail. The inductance of the discharge loop is minimized using a water capacitor arrangement. A very high specific optical power (90 MW/l) is achieved in an active volume of 1.2 l. The pulse energy exceeds 5 J in a 45 ns pulse (FWHM). Komatsu Ltd., Manda 1200, Hiratsuka-shi, Kanagawa 254, Japan Institute of Optics and Fine Mechanics, Department of Plasma Physics, Academia Sinica, Shanghai, P.R. China     

X-ray preionized CO2 laser

A short pulse (100 ns) high-energy x-ray source has been used to preionize a transversely excited carbon dioxide gas discharge laser of 600 cm³ active volume. The maximum output power of 60 MW in a 50 ns FWHM pulse was achieved from a CO₂–N₂–He–CO–Xe static gas mixture at 600 Torr pressure. The energy conversion efficiency was 6%.     

High pressure X-ray preionized TEMA-CO2 laser

The construction of a high-pressure (up to 20 atm) transversely excited CO₂ laser using transverse X-ray preionization is described. High pressure operation was found to be greatly improved in comparison to UV-preionized systems. Homogeneous discharges have been achieved in the pressure range 5–20 atm, yielding a specific laser output in the order of 35 J/l.     

High efficiency discharge-pumped XeCl laser

Received: 19 March 1997/Revised version: 7 August 1997     

High-pressure behaviour of an X-ray preionized discharge pumped XeCl laser

The output characteristics are described of an X-ray preionized discharge pumped XeCl laser, fed by a low-impedance pulse forming line (PFL), at pressures up to 12 bar. The influence of a multichannel rail gap placed between the PFL and the laser head on the output energy was studied. We found an increase of output energy with increasing pressure up to 8 bar. At higher pressures a saturation behaviour was found. The maximum output energy per unit volume was 6.5 J/l.     

XeCl laser excitation by high power microwave pulses

Considerable progress of microwave pumping of excimer laser gas mixtures has been achieved. The present measurable best values for the pulse energy lie in the mJ range. A microwave pulse compression technique is applied using a resonantly charged microwave cavity. The stored energy is extracted by igniting a high density plasma in a quartz tube which acts as a switch and as a laser amplifier yielding a high energy laser pulse.Presented at LASERION '91, June 12–14, 1991, Müchen (Germany)     

Performance improvement of an x-ray preionized XeCl laser of very small discharge volume

Increasing the preionization electron density is found to be an effective method for improving the output performance of discharge-pumped excimer lasers at high gas pressures when the power-supply voltage becomes a limiting factor. In a small volume (2 cm³), x-ray preionized discharge, orders of magnitude improvement in XeCl laser power output (up to 400 kW) and pulse energy (up to 26 mJ) over previously reported results have been found possible using this method. Modifications to the low energy x-ray source and discharge system leading to these improvements are described. Various laser output characteristics are also presented and discussed.     

Importance of pre-ionisation for the non-chain discharge-pumped HF laser

The importance of pre-ionisation for the non-chain discharge-pumped HF laser is studied through experiments on an X-ray photo-triggered laser using mixtures of Ne, SF₆, and ethane. The discharge dynamic in Ne/SF₆ mixtures or pure SF₆, as well as the stabilisation effect induced by C₂H₆ and consequences for the laser performance, are investigated for pre-ionisation electron density values, n_eo, ranging from 10⁶ cm^-3 up to 10⁹ cm^-3, as well as for the so-called discharge self-breakdown mode. Without ethane, the minimum n_eo value which is needed to complete 100% homogeneous charge deposition in the plasma is a very sharply increasing function of the SF₆ pressure. This hinders performance optimisation when the molecule used to react with F-atoms, for instance H₂, has no effect on the discharge dynamic. The minimum ethane partial pressure that is needed to stabilise the discharge depends on n_eo, the pumping pulse duration, the deposited electric charge, and the SF₆ pressure. Discharges in Ne/SF₆ can be much more efficiently stabilised by addition of a small amount of ethane than by an increase of n_eo. A pre-ionisation density as low as 10⁶ cm^-3 is sufficient to achieve the maximum laser energy value, but total suppression of the pre-ionisation has a detrimental effect on the active medium homogeneity. Received: 30 May 2000 / Revised version: 9 October 2000 / Published online: 9 February 2001     

A single-mode KrF laser

Single-mode operation of a KrF laser oscillator has been achieved for the first time. The laser medium is pumped by an electron beam which allows excitation for a much longer duration than with discharge pumping. The long excitation time, together with the use of a short oscillator cavity with a low single-pass gain, allows many roundtrips before saturation is reached. This makes line-narrowing easier and single-mode operation has been achieved using only two intracavity etalons.Technical Research Centre of Finland, Helsinki, Finland     

用于ps脉冲放大的大口径放电泵浦KrF激光器

 以简单的火花间隙作为放电开关，建立了一种用于ps脉冲激光放大的大口径放电泵浦KrF准分子激光器。该激光器的有效增益口径截面为4cm×3cm，在自由运转情况下最大激光输出能量为1.3J，脉宽20ns。用作ps放大器时，利用光学偏振放大方式获得了激光能量140mJ，脉冲宽度10ps的激光输出。利用XeCl激光泵浦的染料激光作为探针测量了不同放电条件下和不同气分比条件下激光的增益和吸收系数。     

KrF laser system with corrected pulse front and compressed pulse duration

A high-power KrF laser system is presented providing 45 mJ, 150 fs pulses at the position of a target. Pulse front distortion is avoided by specially designed refractive optics. Pulse compression is done after final amplification using a simplified compressor.Dedicated to Prof. Dr. Herbert Welling on the occasion of his 60th birthdayPolska Akademia Nauk, Instytut Chemii Fizycznej, Kasprzaka 44/52, PL-01-224 Warszawa, Poland     

Self-consistent modelling of X-ray preionized XeCl-laser discharges

In this theoretical work a 0-D model for a self-sustained X-ray preionized XeCl-laser discharge is presented. The model is self-consistent in the sense that it simultaneously solves, contrarily to the usual decoupling procedure, the Boltzmann equation for electrons, the kinetic equations for excited and ionic species, the equations for the electrical circuit and the laser photon density. It includes a rather complete kinetics of HCl(v) vibrational excitation, dissociation and dissociative attachment. The influence of electron collisions with excited species and of e-e Coulomb collisions on the plasma parameters and transport coefficients is discussed. Some evidence of the non-stationary equilibrium between the electron distribution and the reduced electric field E/N is given. Results of the model are compared with experimental ones corresponding to a XeCl-laser discharge driven by a L-C inversion circuit. The model predicts well the main trends for the variation of the laser energy in a large range of experimental conditions. The discrepancy between experiment and model for absolute values of the laser energy is discussed.     

On the performance of an ArF and a KrF laser as a function of the preionisation timing and the excitation mode

An X-ray preionised ArF and KrF excimer laser has been studied with three different spiker-sustainer excitation circuits. We observed large differences in the laser performance, when the preionisation delay timing was varied on a nanosecond timescale. The behaviour of both lasers was found to be equivalent. The observations can be understood by considering the effect of the discharge excitation technique on the preionisation process. An excitation mode with a prepulse well above the steady-state voltage V_SS with a subsequent reversed overshoot voltage for initiating the discharge, in combination with a well-timed preionisation pulse is found to give the best results. Optimum output energies of 50 mJ with ArF and 175 mJ with KrF were obtained from an active volume of 60×1.5×1.2 cm in the so-called swing mode, with the preionisation applied 60 ns before the discharge breakdown. Received: 23 February 1999 / Revised version: 4 June 1999 / Published online: 16 September 1999     

Miniaturization of a thalliumiodide photodissociation laser

We report on the operation of a thallium photodissociation laser with an active medium in the form of a thin layer on a quartz wall. Laser emission has been obtained with layer thicknesses below 100 m. This gas laser seems to be feasible with an active volume as small as 10^–1 to 10^–2 mm³.     

Subpicosecond UV pulse generation for a multiterawatt KrF laser

A 180-fs UV pulse has been generated based on a hybrid synchronously pumped mode-locked dye laser for a multiterawatt KrF laser system. The pulse width was measured by the single shot autocorrelation technique with the three-photon fluorescence of the XeF C-A transition. The pulse width broadening due to dispersive media was investigated. The results show that the observed pulse width broadening from 210 fs to 390 fs through the entire system is explained mostly by the linear dispersion of the optical elements for near-transform-limited input pulses.     

The catalytic activity of gold-plated electrodes in a slab-geometry CO2 laser

2 laser in a slab geometry with a heated gold-plated electrode is shown. The catalytic activity of the gold electrodes to regenerate the laser gas can substantially increase the optimum output power of the CO₂ laser. An output power of 116 W is obtained for a slab that was 370 mm long and had a cross section of 2.5 mm×15 mm. Received: 18 July 1996     

Discharge pumped C1F laser at 285 nm

This paper reports on experiments carried out in order to improve the performance of the TEA discharge pumped C1F uv laser at 285 nm. Factors which influence the gas degradation with increasing operating time, resulting in a decrease of laser output power, were investigated, aiming at a better understanding of the relevant mechanisms. By optimizing several parameters, laser pulse energies beyond 25 mJ were obtained in a high-pressure discharge laser chamber. C1F lasing has also been demonstrated in a commercially available multigas TEA laser system.As a byproduct of our C1F experiments, laser action on the correspondingDA transition of Cl₂ at 258 nm has also been achieved for the first time in a discharge laser chamber.     

Competitive processes in T1 anti-stokes raman laser system

The limiting processes in the anti-Stokes Raman Laser (ASRL) are investigated in a Tl ASRL system. The detailed mechanisms and dynamics of ASRL action, photoionization, stimulated collision-induced fluorescence, collisional quenching and other radiative processes are determined, showing the competition among these processes for different experimental parameters.     

Non-equilibrium vibrational,attachment and dissociation kinetics of HCl in XeCl selfsustained laser discharges

The vibrational kinetics of HCl in a Ne-buffered XeCl selfsustained laser discharge is self-consistently calculated by coupling the vibrational master equation with the chemical one, the Boltzmann equation for electron transport and the circuit equations. The results show the limits of the classical simplified schemes of HCl vibrational kinetics used in the literature. Problems connected with the neglection of HCl depletion instabilities in the calculations are discussed using a parallel resistor network model.