Pulsed chemical lasers initiated by laser photolysis

Abstract

Use of laser photolysis for initiation of pulsed chemical lasers is described. In laser-initiated chemical lasers, the transient photochemical state evolves from a well-defined initial state without obscurant time variation of photolysis products. Spatial confinement of the initiating radiation reduces undesired effects of reflections from the enclosure walls and permits near coincidence between the reactant volume and that of the fundamental cavity mode. Application of the laser-initiation technique to an HF laser pumped by H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> + F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> chain reactions is discussed. Two distinct time regimes are found in the HF laser transient. The laser intensity in the initial regime exhibits large amphtude pulses characteristic of unsteady oscillations in high-gain media, whereas the relatively low-levels intensity in the second regime exhibits long-term variations characteristic of quasi-steady changes induced by reaction-deactivation processes. Variation of intensity features in both time regimes with physical parameters governing the photochemical state of the reactant media is described.