No abstract

No abstract

Spatially resolved gain measurements at 10.6μ have been made transverse to the discharge in an axially flowing CO2 laser amplifier. These show a nonuniform gain throughout the discharge with maximum gain at the upstream end of the positive column. Increasing the flow velocity shifts the gain profile and leads to an over-all increase in gain. Spatial intensity profiles of the sidelight emission of CO2 at 4.3μ, CO at 0.48 and 2.3 μ, and N2 at 3371 Å are shown.

Several authors have reported the observations of frequency broadening in filaments which were produced by the self-focusing of a Qsw.tched laser in liquids. 1 ** This broadening has been attributed to the generation of new frequency components through an intensity-dependent refractive index and stimulated Rayleigh scattering. 1 * 4 Theories of the frequency broadening in an optical pulse by an intensity-dependent refractive index have been given in connection with the pulse distortion.''* But comparison of experiment with theory has been difficult, because the broadening is usually irregular and the observation of the spectrum in filaments is obscured by the strong background. We report here the observation of the frequency broadening in a filament with short duration time, under such experimental conditions that the intensity of the stimulated Raman emission ir the filament is much less than that of the laser. The structure of the frequency spectrum shows a pattern which can be explained by phase modulation through the intensity-dependent refractive index.

Spatially resolved gain measurements at 10.6 μm have been made transverse to the discharge in an axially flowing CO2 laser amplifier. The composition of the amplifier medium has been varied to include initially pure CO2, binary mixtures of CO2:CO, CO2:He, and CO2:N2, and triple mixtures of CO2:N2:He. Strong spatial variations of gain are observed which depend on the gas mixture, flow rate, temperature, pressure, and current. Corresponding spatial intensity profiles of the sidelight emission of CO2 at 4.3 μm are shown.