Narrow linewidth passband filters and UV laser source for rotational Raman imaging
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We present two novel narrow passband spectral filters capable of frequency resolved imaging of rotational Raman light scattering with strong spectral rejection of out-of-band Raman, Rayleigh and Mie scattering. The first filter, capable of 2-D imaging and spectral selectivity, is based on mercury vapor absorption and subsequent resonant fluorescence. The second filter exploits the variation in the index-of-refraction near resonance to spatially resolve small spectral shifts. It is capable of simultaneous 1-D measurements of multiple frequencies. Each filter has a spectral sensitivity of better than 1cm -1. The filters are paired with an injection seeded, cavity locked, frequency tripled Ti: Sapphire laser which produces > 30 mJ/pulse of single mode, tunable light in the vicinity of 253.7 nm. The laser and resonant fluorescence filter are combined to spectrally resolve scattering from individual rotational Raman lines of nitrogen and oxygen. A description and characterization of each filter is given.
name of conference
Optical Technology in Fluid, Thermal, and Combustion Flow III