Abstract

Laser Induced Fluorescence (LIF) techniques are used for determining the properties of oxygen bearing wind tunnel flowfields. The 193 nm (ArF) output of a tunable excimer laser is well suited for exciting the oxygen Schumann Runge bands. However, the performance of the excimer laser is critical because of the complex, high-temperature, chemically reacting flows of interest. The standard narrowband excimer laser output is approximately 90 percent narrow band and 10 percent broadband. Additional transitions will be excited because of this broadband output, resulting in erroneous fluorescence measurements. This paper will describe improvements to a Lambda Physik EMG150 excimer laser in order to correct this and other deficiencies. The laser operates in the single-pass oscillator amplification mode, eliminating the broadband amplifier output. A computer-controlled tuning device tunes the laser, and by monitoring reference cell LIF, the laser is locked onto the desired transition. Dual-wavelength output is achieved with an additional set of tuning optics, eliminating the need for a second laser for temperature measurements. Experimental oxygen and nitric oxide excitation spectra will be presented to illustrate the improved laser performance.

© 1993 Optical Society of America