SPATIAL GAIN MEASUREMENTS IN A CHEMICAL OXYGEN-IODINE LASER (COIL)

The spatial distribution of small signal gain has been investigated on the RADICL device, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F = 3 --> F = 4 hyperfine levels of the (P-2(1/2)) to (P-2(3/2) ) spin-orbit transition in atomic iodine was used as a small signal pr obe. A peak gain of 1.2%/cm was measured along the horizontal centerli ne of the single-slit, supersonic nozzle, which is about two times gre ater than measurements made on ReCOIL by Hager ef at and compares favo rably with measurements made on the RotoCOIL device by Keating st al. Gain distribution was investigated under three I-2 flow conditions. Sc ans across the supersonic expansion indicate a gradient in gain distri bution due to higher gas temperatures along the walls and mixing pheno mena.