Optical bistability at low light level due to collective atomic recoil

TL;DR

This paper reports on optical bistability at extremely low light levels achieved through collective atomic recoil in an ultracold gas, enabling dynamic control of optical properties without a cavity.

Contribution

It introduces a novel scheme combining recoil-induced resonance and waveguiding to achieve high atomic cooperativity and optical bistability at picowatt power levels.

Findings

Optical bistability observed at 20 pW input power.

Achieved collective atomic cooperativity of 275 ± 50.

Experimental results agree with theoretical model.

Abstract

We demonstrate optical nonlinearities due to the interaction of weak optical fields with the collective motion of a strongly dispersive ultracold gas. The combination of a recoil-induced resonance (RIR) in the high gain regime and optical waveguiding within the dispersive medium enables us to achieve a collective atomic cooperativity of $275 \pm 50$ even in the absence of a cavity. As a result, we observe optical bistability at input powers as low as 20 pW. The present scheme allows for dynamic optical control of the dispersive properties of the ultracold gas using very weak pulses of light. The experimental observations are in good agreement with a theoretical model.