Temporal intensity correlation of light scattered by a hot atomic vapor

Abstract

We present temporal intensity correlation measurements of light scattered by a hot atomic vapor. Clear evidence of photon bunching is shown at very short time-scales (nanoseconds) imposed by the Doppler broadening of the hot vapor. Moreover, we demonstrate that relevant information about the scattering process, such as the ratio of single to multiple scattering, can be deduced from the measured intensity correlation function. These measurements confirm the interest of temporal intensity correlation to access non-trivial spectral features, with potential applications in astrophysics.

Generation of ideal thermal light in warm atomic vapor

“…transition followed by the spectral filtration by the Fabry-Pérot resonator with independently measured transmission bandwidth. The frequency bandwidth Δν=65±3MHz (FWHM) of detected light has been estimated by numerically evaluating the temporal width of the measured g (2) (τ) function [25], in good agreement with the independently measured transmission width of the optical filtering cavity Δν FP =67±7 MHz.…”

“…The overall temporal length of the generated thermal light is substantially broadened by the contribution of the single-atom or few-atom scattering processes. As demonstrated in [25,50], the contribution of the single atom scattering process to the observed g (2) (τ) can be suppressed by maximization of the effective optical thickness, which can be achieved by resonant excitation and high atomic density. We have further examined the dependence of the overall generated field frequency bandwidth and possibility of keeping the observability of the ideal photon bunching on several crucial parameters determining the interaction of light with atomic vapor and relative contribution of the single to multi-atom scattering.…”

“…The excitation laser power has been set to P=39 mW and the atomic cell temperature is corresponding to effective optical depth OD=1.19±0.08. The observed temporal shape corresponds to two scattering processes, single-atom scattering and multi-atom scattering of detected photons, which give rise to two characteristic extents of reconstructed spectral widths [25,42]. The presented data have been fitted using a simple theoretical model comprising two Gaussian spectra and the optical cavity filter with Lorentzian profile resulting in the estimated ratio of single to multi-photon scattering of 0.15.…”

“…The frequency bandwidth of the detected light field has been estimated from the observed time spread in g (2) (τ), which gives the temporal standard deviation σ τ =13±2 ns corresponding to the frequency width σ ν =110±20 MHz. The σ τ and σ ν were evaluated following the calculation presented in Dussaux et al [25]. The detailed experimental studies of the dependence of generated thermal light bandwidth and detected photon rate on parameters which determine the interaction of light with atomic vapor can be found in the appendix.…”

“…A number of experimental teams have recently attempted to realize a thermal light source with large spectral bandwidth either as a principal resource or as a side result of attempts to engineer a nonlinear interaction with a high degree of mode purity [12,[25][26][27][28][29][30][31]. Out of these, the sources utilizing the process of amplified spontaneous emission [12,[29][30][31] seem to offer technically feasible spectral bandwidth in a few nanometer regime.…”