Gas phase and plasma diagnostics based on resonant atomic vapor filters

This thesis presents advances in gas phase and plasma diagnostics based on resonant atomic vapor filters. Variation in the index of refraction of an atomic vapor can lead to strong absorption and dispersion of near resonant light. We use such vapors as optical filters to enable non-intrusive laser diagnostics.; We extend the filtered Rayleigh scattering (FRS) technique from the visible to the ultraviolet portion of the spectrum. A mercury filter is paired with a titanium sapphire laser at 253.7 nm. The filter offers strong background suppression, and provided a means of probing the scattering lineshape. Temperature may be measured by scanning the lineshape across the filter, and deconvolving the filter profile from the scattering signal. The technique is verified with air temperature measurements at several conditions. We find good measurement accuracy even at low pressures (50 torr). A comparison of visible and ultraviolet FRS is given, and a figure of merit for filter comparison is developed.; The FRS technique is applied in plasmas for the first time. We perform point temperature measurements in weakly ionized glow discharges, of argon, and argon/nitrogen mixtures. Temperature is measured as a function of current, and radial profiles are obtained by displacing the discharge tube. The FRS measurements show good agreement with straight Rayleigh measurements, and with computation. By focusing the laser into a sheet, a similar approach is used for planar measurements. We repeat the radial profiles of the diffuse discharges, and find good agreement. We study a contracted argon discharge. Temperature profiles are measured at several currents, and from them we could infer the width of the current distribution.; New filter concepts based on spatial and temporal dispersion are presented. A prism shaped spatial filter disperses spectral information in one dimension, while another dimension may be used for spatial imaging. The filter also offers strong background suppression. These characteristics make the prism filter well suited for rotational Raman diagnostics. We demonstrate the utility of the filter by dispersing the rotational Raman spectrum of CO ₂.; A temporally dispersive filter configuration is used to characterize laser seeding efficiency, and may enable novel laser diagnostics. Group velocity dispersion (GVD) provides a means of transforming spectral information to the time domain. Such approaches may allow direct measurements of scattering or fluorescence lineshapes with standard nano-second detectors. The technique is demonstrated by chirping pulses due to low pressure, and high pressure Rayleigh scattering.