Ground-state grating echoes from Rb vapor at room temperature

Abstract

We have used two sets of opposite circularly polarized traveling wave pulses separated in time to establish, and subsequently rephase, a spatially modulated coherence between the magnetic sublevels of the Fϭ3 ground state in Doppler broadened 85 Rb vapor. The rephasing results in a magnetic grating echo whose duration is an accurate measure of the velocity distribution. We demonstrate that the time scale of the experiment is determined solely by the transit time of atoms across the laser beam. The shortening of the lifetime due to a perturber ͑Ar͒ allows us to infer the Rb-Ar velocity changing collision cross section.

Detection of nonresonant impurity gases in alkali vapor cells

“…It was recently shown that coherence among ground state Zeeman sublevels of Rb atoms can be used for detection of a perturbed ͑Ar͒ in an atomic cell. 6 In this experiment, the cross section for Rb-Ar velocity-changing collisions was inferred from properties of coherence grating echoes. 7 However, photon echoes are essentially transient phenomena with a complicated experimental implementation.…”

Prospects for Precise Measurements with Echo Atom Interferometry

“…This is analogous to the reversal of the Doppler phases of individual atoms in a traditional two-pulse photon echo experiment [150] that can be used for measuring the excited state lifetime [151]. In the absence of decoherence due to collisions and background light, the MGE amplitude should decay on a time scale determined by the transit time of atoms through the laser beams [149].…”

“…A magnetic grating echo (MGE) is observed using a second set of excitation pulses at t = T to rephase the coherence grating, as in Fig. 14(c) [147][148][149]. The second pulse modifies the time-dependent coefficients that describe the coherent superposition of magnetic sublevels so that the grating reforms at t = 2T.…”

“…The focus of initial experimental work using the MGE was related to observing effects due to atomic recoil [148]. The MGFID and MGE were used to verify the expected dependence of the dephasing time of the coherences on the velocity distribution of the sample [148,149], observing the effect of magnetic fields for particular experimental configurations [148], and studying the effects of collisions [149]. Other applications of the MGFID include measurements of the diffusion constants [152] and phase space imaging [153].…”

Accurate Determination of an alkali-inert gas diffusion coefficient using coherent transient emission from a density grating

“…The signal scattered from this coherence grating will have the same time constant as for the case of perpendicular linear polarizations. The dephasing time of the grating has been used to measure the velocity distributions of warm vapor [31,32], cold atomic gases [32,33], and atomic beams [34].…”