ANALYTICAL MODEL FOR INJECTION-CONTROLLED EXCIMER LASER-AMPLIFIERS

A semiempirical model of a pulsed, injection-controlled laser is investigated analytically and is applied primarily to extensive experimental results that have been obtained for the XeF(C &rarr A) excimer laser. The gain medium inside an unstable cavity is represented by a folded pulsed amplifier which is seeded by a narrowband input signal. A set of coupled rate equations for the population densities of the upper laser states, the wideband absorbers, and the photon flux was numerically integrated. Measured gain and absorption of the amplifier were used as input data to evaluate the model. Excellent agreement between calculated and experimentally observed peak intensity and various other pulse characteristics such as pulse shape and laser pulse delay time was obtained. This model also predicts the experimentally determined injection-control threshold for KrF excimer lasers successfully, and should be applicable to numerous other injection seeded lasers.