Aerodynamic window performance and optical quality

Abstract : The aerodynamic window is a viable means of exiting the high-power beam from a low-pressure laser cavity. It consists of a supersonic jet which spans an opening in the laser cavity wall sealing the cavity from ingestion of ambient air. The differential pressure force across the opening is balanced by a change in jet momentum while the beam passes through the aerodynamic window flow field transversely to the direction of flow of this jet. In evaluating the performance of the aerodynamic window the areas of primary concern are: (1) the ability of the aerodynamic window to transmit the laser beam with minimum beam degradation, (2) the amount of mass flow required to effect the aerodynamic seal, and (3) the effectiveness of the aerodynamic window in sealing the cavity from ingestion of ambient air. The technical investigation discussed herein is directed toward the first two areas of concern.