Enhanced frequency up-conversion in Rb vapor

TL;DR

This paper reports a highly efficient method for generating coherent blue light at 420nm through frequency up-conversion in rubidium vapor, achieving unprecedented conversion efficiency by optimizing laser parameters and exploring resonance conditions.

Contribution

It introduces a novel high-efficiency up-conversion technique in rubidium vapor, with detailed analysis of resonance effects and phase matching for optimal blue light generation.

Findings

Achieved 260%/W single-pass conversion efficiency.

Blue light generation peaks near 85Rb two-photon resonances.

High vapor pressure suppresses coherent light in certain spectral regions.

Abstract

We demonstrate highly efficient generation of coherent 420nm light via up-conversion of near-infrared lasers in a hot rubidium vapor cell. By optimizing pump polarizations and frequencies we achieve a single-pass conversion efficiency of 260% per Watt, significantly higher than in previous experiments. A full exploration of the coherent light generation and fluorescence as a function of both pump frequencies reveals that coherent blue light is generated close to 85Rb two-photon resonances, as predicted by theory, but at high vapor pressure is suppressed in spectral regions that do not support phase matching or exhibit single-photon Kerr refraction. Favorable scaling of our current 1mW blue beam power with additional pump power is predicted.