Application of a single-frequency unstable cavity to a CW HF laser

Demonstrations of diffraction-limited performance from a CW diffusion-type HF chemical laser are reported. A novel type of edge-coupled nonconfocal unstable resonator consisting of a convex mirror and a diffraction grating is used. A new technique of coupling power out of an unstable resonator different from the edge coupling previously suggested by Siegman is also applied. This consists of coupling power out directly through the diffraction grating zero-order radiation. By this technique, a large fraction of the total power is concentrated within the diffraction-limited main lobe. Peak power levels of the order of 100 W have been achieved on a single line [ ] for flow conditions yielding approximately 1 kW in closed cavity measurements.