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1 February 1991 Laser-induced medium perturbation in pulsed CO2 lasers
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Proceedings Volume 1397, 8th Intl Symp on Gas Flow and Chemical Lasers; (1991)
Event: Eighth International Symposium on Gas-Flow and Chemical Lasers, 1990, Madrid, Spain
The phenomenon known as laser induced medium perturbation (LIMP) or mode-medium interaction (MMI) is responsible for a loss of nearly 50% of the output energy from a focussed far-field spot in some pulsed CO2 lasers. A simple theory was previously developed to explain this result in terms of the formation of a phase grating in the gain medium due to enhanced vibrational-translational (VT) relaxation heating in regions where the intracavity flux is high. Attempts to employ this simple theory to model recent experimental results and predict and avoid the onset of this loss mechanism in the design of long pulse CO2 lasers demonstrated that it was inadequate for several reasons. In the present work, these shortcomings are examined and a new model is presented which incorporates wave optics and hydrodynamic relaxation effects. The results of calculations with this new model (time dependent Strehl ratio and pressure dependence) are in good agreement with experimental data for both electron-beam sustained and UV-preionized CO2 discharge lasers. This model is capable of determining laser design points which essentially eliminate the far-field energy loss.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Gregory C. Dente, Robert F. Walter, and Daniel Gardner "Laser-induced medium perturbation in pulsed CO2 lasers", Proc. SPIE 1397, 8th Intl Symp on Gas Flow and Chemical Lasers, (1 February 1991);

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