Slow Light Prism Enhanced Spectroscopy (SLOPES)

We report a new spectroscopy method achieved by combined refraction and propagation delay of light pulses passing through a prism cell filled with an atomic vapor. The atomic vapor medium has strong refractive index gradients near the atomic resonant absorption features, and these features enable the separation in time and space of different spectral features of a light pulse propagating through the vapor cell. The gradient of the refractive index leads to a slowing of the light pulse, while simultaneously, the magnitude of the refractive index and the prismatic windows or internal prism elements of the atomic vapor cell spatially separate the frequencies due to dispersion. The combination of these two effects leads to high-resolution spectral selectivity and strong suppression of out-of-band light. Applications are achieved for Rayleigh, Raman, and Thomson spectroscopy for which the wavelength of the scattering spectra tracks the wavelength of the excitation laser source. The laser is tuned such that the spectral line of interest falls near the resonance of the atomic vapor. Applications for rotational Raman spectroscopy are of particular interest since specific Raman lines can be selected while other Raman lines as well as background Rayleigh and other scattering are strongly rejected.