Controllable ultra-broadband slow light in a warm Rubidium vapor

TL;DR

This paper demonstrates controllable ultra-broadband slow light in warm Rubidium vapor, achieving tunable delays with minimal absorption and pulse distortion, supported by a simple theoretical model.

Contribution

It introduces a method to control group delay in Rubidium vapor across a broad spectral window with minimal absorption and validates it with a simple, accurate theoretical model.

Findings

Achieved a fractional delay of 18 with 250 fs pulses.

Maintained small absorption (<1%) across a several-nm window.

Theoretical model matches experimental results closely.

Abstract

We study ultra-broadband slow light in a warm Rubidium vapor cell. By working between the D1 and D2 transitions, we find a several-nm window centered at 788.4 nm in which the group index is highly uniform and the absorption is small (<1%). We demonstrate that we can control the group delay by varying the temperature of the cell, and observe a tunable fractional delay of 18 for pulses as short as 250 fs (6.9 nm bandwidth) with a fractional broadening of only 0.65 and a power leakage of 55%. We find that a simple theoretical model is in excellent agreement with the experimental results. Using this model, we discuss the impact of the pulse's spectral characteristics on the distortion it incurs during propagation through the vapor.