Dispersion of Rayleigh Scattering with a Multi-Prism Atomic Vapor Cell

Abstract

The dispersion effects caused by refractive index gradients of atomic vapors such as mercury, rubidium, cesium, potassium and sodium can be used for dispersion of Rayleigh scattering. A multi-prism atomic vapor cell based technique has multiple surface interactions between the glass and atomic vapors, causing large dispersion of the scattering in the vicinity of atomic resonances. In such configurations it is essential to reduce the losses caused by the optical elements. The spectral line-shape of Rayleigh scattering collected from a region of interest can be spatially resolved by capturing it at a certain distance from the dispersion cell on a camera. This approach leads to an instantaneous measure of the Rayleigh line shape and thus the temperature. The shift in the total line shape spectrum can provide velocity and the integrated profile yields density. The laser needs to be tunable and narrow line-width so that the Rayleigh scattering return can inturn be tuned to overlap the region of interest in the vicinity of the atomic resonances. Non linear dispersion curves outside the absorption region can be tuned by controlling the temperature of the atomic vapors, the detection system can therefore be optimized to increase the resolution of the measurement. By using a multi prism configuration placed at sequential angles of minimum deviation the non linear dispersion can be amplified. An analysis is done to understand the experimental requirements, feasibility of optical elements that can be practically employed for construction of a cell. Different variables of interest to control and optimize the desired resolution of detection are evaluated.