Theory of an electronic-phototransition chemical laser with thermal initiation behind a shock wave front

A theory is developed of an electronic-phototransition cw chemical laser initiated by a shock wave in a dense reagent stream. Calculations are made of the population inversion behind the shock wave front in the case of photorecombination reactions. The formation of a waveguide which localizes the lasing mode in the inversion zone is demonstrated. Calculations are made of the optical gain a of the waveguide modes. In an analysis of the gas dynamics and chemical kinetics of the laser action an allowance is made for a light-stimulated chemical reaction which alters the spatial dependences of the density, temperature flow velocity, and concentrations of the reagents. The specific optical power P extracted from the stream is determined as a function of the optical losses. Various specific gas mixtures are analyzed and the three most promising for laser applications are selected: NO₂Cl–Ar, O₃–Ar, and O₃–CO. It is shown that an inversion is established for these mixtures over a wide wavelength range and the waveguide formation conditions are compatible with the inversion condition. A gain α≈10^–3cm^–1 and power ~100 kW per 1 cm² of the gas stream are predicted for these mixtures.