Transient dynamics and momentum redistribution in cold atoms via recoil-induced resonances

TL;DR

This paper investigates recoil-induced resonances in cold atoms within a magneto-optical trap, revealing how atomic response time and momentum redistribution influence transient gain spectra and proposing their use to enhance nonlinear atom-photon interactions.

Contribution

It introduces a detailed experimental and numerical study of RIRs in the transient regime, highlighting mechanisms of momentum redistribution and their potential for atomic momentum engineering.

Findings

Transient hysteresis affects gain spectra depending on chirp sign.

High-intensity pulses cause persistent momentum hole-burning.

Numerical models agree with experimental observations.

Abstract

We use an optically dense, anisotropic magneto-optical trap to study recoil-induced resonances (RIRs) in the transient, high-gain regime. We find that two distinct mechanisms govern the atomic dynamics: the finite, frequency-dependent atomic response time, and momentum-space population redistribution. At low input probe intensities, the residual Doppler width of the atoms, combined with the finite atomic response time, result in a linear, transient hysteretic effect that modifies the locations, widths, and magnitudes of the resulting gain spectra depending on the sign of the scan chirp. When larger intensities (\textit{i.e.}, greater than a few $\mu$W/cm$^2$) are incident on the atomic sample for several $\mu$s, hole-burning in the atomic sample's momentum distribution leads to a coherent population redistribution that persists for approximately 100 $\mu$s. We propose using RIRs to engineer the atomic momentum distribution to enhance the nonlinear atom-photon coupling. We present a numerical model, and compare the calculated and experimental results to verify our interpretation.