Thermal-instability considerations for pulsed microwave-excited CO₂slab lasers

Abstract

The effect of thermal instabilities on the performance of sealed-off microwave-excited CO2 slab lasers is analysed. The evolution time of the thermal instability (τ) is estimated for both helium-rich and -poor mixtures. The analysis is based on a simplified discharge model. The dependence of τ on the reduced field (E/N), the discharge gap, the gas pressure, and the ballast-strip characteristics is derived for helium-rich and -poor mixtures. Equating τ and tp, the temperature rise time from ambient to a most efficient gas-discharge temperature, results in an optimal ballast-strip capacitance. This result is found to be independent of the gas mixture and pressure. Two examples for optimized ballast dielectric strips (fused quartz and alumina) are presented.

Longitudinal coupled‐cavity scheme for microwave‐excited CO2 slab lasers

“…The tube serves as the discharge chamber, and also as the stabilizing ballast dielectric-strip required for microwave discharges. The Pyrex tube wall-thickness is designed to avoid the evolvement of thermal instabilities [24]. Two laser mirror holders are attached to the Pyrex tube by silicon microwave-proof O-rings.…”