Princeton University

Plasma Tec, Inc.

Walter R Lempert

Richard B Miles

Noah Finkelstein

A method and apparatus for collecting and analyzing Raman scattered light includes an atomic vapor cell (,) configured to spectrally disperse light by resonant dispersion while simultaneously suppressing Rayleigh scattering and other background scattering through resonant absorption. A light source (,) is used to illuminate a sample (,). The light source (,) is tuned in the vicinity of the absorption feature of some atomic vapor. The resonant dispersion of the vapor is well known to strongly vary in the vicinity of such an absorption feature. If the light source (,) is tuned in the vicinity of the absorption, then the Rayleigh light is strongly attenuated. The Raman light is transmitted through the filter. If the filter is constructed so that the dispersive nature of the atomic vapor in the vicinity of the absorption line bends the light rays as they pass through the atomic vapor cell (,), then the Raman light can be spatially displaced.

Dispersive atomic vapor raman filter

First and second relatively high power laser beams are directed into a volume enclosing a flow field of molecules of a molecular species. The beams are focussed to form an overlapping region of the beams in the flow field, for tagging a portion of the associated molecules by driving them into their first vibrational state by stimulated Raman pumping. A high intensity beam of light is directed into the flow field proximate the overlap region for intercepting the tagged molecules, and causing them to fluoresce, thereby permitting their displacement to be measured through observation thereof, for determining the velocity of the associated molecules and flow field.

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Mercerville, NJ, United States of America

Walter R Lempert