Numerical Simulation on the Amplification of Picosecond Pulses in Multiatmosphere CO₂ Laser Media

Abstract

Properties of the picosecond pulse amplification in a multiatmosphere CO₂ laser are studiedby numerical solutions of the Maxwell-Bloch equations. The coherent effects on theshort pulsepropagation originated from the discreate structure of the vibrational-rotational spectrum of a CO₂ molecule are described in detail. The characteristics of amplifier gain, saturation, and pulseshape depend on the degree of matching of a pulse spectrum with a gain spectrum. At relativelylow pressures, a train of pulses is created in a small-signal gain regime. Effective small-signalgains and effective saturation energies are obtained for various gas pressures by fitting the Frantz-Nodvik equation to the results of the model. Isotope mixtures of CO₂ are also discussed to obtaina continuous gain spectrum at relatively low gas-pressures.