Studies of an injection controlled rare gas halide excimer laser

Abstract

Characteristics of an injection-controlled electron-beam pumped XeF(C $\to$ A) excimer laser have been investigated with emphasis on efficient wideband tuning and scaling issues. Using a quasi-cw dye laser as an injection source, data were obtained that describe the laser characteristics over a wide parameter range. A high-Z electron-beam backscattering reflector inside the laser reaction cell improved the electron-beam energy deposition by 40%, resulting in an increase of the amplified laser output by more than a factor of four. Laser intrinsic efficiency was investigated by varying electron-beam pump energy, and the energy deposition value of $\sim$90 J/l was found to be optimum for 10 ns electron-beam pumping condition. Initial geometric scaling experiment indicated that the laser output energy scales with the pumping length. Efficient and continuous wavelength tuning between 460 and 510 nm has been achieved with an output energy density of $\sim$1 J/liter, and an intrinsic efficiency of $\sim$1% throughout the entire tuning region. A semi-empirical model of an injection-controlled XeF(C $\to$ A) laser amplifier has been analytically investigated. The gain medium inside an unstable cavity is represented by a pulsed folded amplifier which is seeded by a narrowband signal. A set of coupled rate equations for the population densities of XeF(C) states, the wideband absorbers, and photon flux were numerically integrated. Measured gain and absorption of the amplifier were used as input data for the model. This model showed excellent agreement with experimentally observed peak intensity and various other pulse characteristics. This analysis will be useful in predicting the scaling behavior of the injection-controlled XeF(C $\to$ A) laser as well as for the characterization of other pulsed injection-controlled laser systems. Furthermore, laser beam propagation characteristic based on Fresnel-Kirchhoff diffraction integral has been investigated theoretically in order to predict and to evaluate the laser beam quality. The model is useful in designing an optimum unstable laser resonator combined with the amplifier model, as well as in evaluating the beam quality for experimentally obtained laser outputs