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 probe. A peak gain of 1.2%/cm was measured along the horizontal centerline of the single-slit, supersonic nozzle, which is about two times greater than measurements made on ReCOIL by Hager ef at and compares favorably with measurements made on the RotoCOIL device by Keating st al. Gain distribution was investigated under three I-2 flow conditions. Scans across the supersonic expansion indicate a gradient in gain distribution due to higher gas temperatures along the walls and mixing phenomena.