Coherent amplitude modulation of continuous-wave light in cesium vapor

TL;DR

This paper reports on the observation of coherent oscillations in cesium vapor caused by amplitude modulation of continuous-wave light at 388 nm, revealing potential for probing atomic vapor lasing processes.

Contribution

It demonstrates the detection of sustained oscillations linked to hyperfine level spacing and suggests a new method to probe lasing in atomic vapors using transmitted pump field properties.

Findings

Oscillations occur near hyperfine level spacing of cesium's excited state.

Threshold behavior of oscillation amplitude with pump power.

Infrared emission possibly amplified by retro-reflections.

Abstract

We report on observations of coherent, sustained oscillations in the absorption of continuous-wave light at 388 nm that excites the $6S_{1/2}\rightarrow 8P_{3/2}$ transition in cesium vapor. The oscillation frequency is close to the spacing of hyperfine levels of the $8P_{3/2}$ level that are excited simultaneously by the 388 nm field. We observe threshold behavior of the oscillation amplitude with pump power, and suggest that the effect is associated with infrared directional emission due to amplified spontaneous emission from the $8P_{3/2}\rightarrow 8S_{1/2}$ transition, that is assisted by retro-reflections from the cell windows. The effect may be used to probe a lasing process in an atomic vapor, by checking the temporal properties of the pump field transmitted through the vapor.