Inversionless gain in a lossy medium

TL;DR

This paper demonstrates gain without inversion in a miniaturized rubidium-hydrogen vapor cell, highlighting the effects of cell size and collisions, and suggesting potential for compact laser applications.

Contribution

It presents the first observation of gain without inversion in a miniaturized vapor cell, emphasizing the role of wall collisions and buffer gases in this phenomenon.

Findings

Gain observed in absorption spectra due to coherence effects

Cell miniaturization influences the gain profile evolution

Potential for developing miniaturized lasers without inversion

Abstract

We study gain without inversion due to coherence effects in a Doppler-broadened degenerate three-level system of a rubidium-hydrogen mixture in a miniaturized micron scale custom vapor cell. The cell miniaturization gives rise to collisions of atoms with the walls of the cell. This, combined with the high collision rate with the hydrogen buffer gas allows us to observe gain in the absorption spectra. Furthermore, we analyze the role of cell miniaturization in the evolution of the gain profile. In addition to fundamental interest, the observation of gain without inversion in our miniaturized cells paves the way for applications such as miniaturized lasers without inversion.