A hot gas generator and a multiple nozzle module were employed to simulate the flow of a gas dynamic laser. Interferometric measurements performed with a Fizeau interferometer allow the mapping of density profiles in the cavity region. Density nonuniformities caused by sidewalls and artificial obstructions in the subsonic section of the flow field were observed. Typically, density variations of five to eight percent originated from the shock waves off the sidewall boundary layers. Additional density nonuniformities of about five percent were caused by artificial obstructions arranged directly upstream of the nozzle structure. An explanation is based on heat transfer from the hot gas into the obstruction. To minimize the effect of these medium nonuniformities on optical performance, the obstructions were mounted in a skewed orientation relatively to the optical axis. Interferometric measurements showed excellent cancellation of phase differences across the observation area. Results of numerical resonator calculations including the measured medium inhomogenities show the effect on laser beam quality.

Date Published: 20 June 1989
PDF: 6 pages
Proc. SPIE 1031, 7th Intl Symp on Gas Flow and Chemical Lasers, (20 June 1989); doi: 10.1117/12.950517

Published in SPIE Proceedings Vol. 1031:
7th Intl Symp on Gas Flow and Chemical Lasers
Dieter Schuoecker, Editor(s)