Up-conversion of 780 nm or 795 nm laser radiation to 420 nm in rubidium atomic vapor

Abstract

We demonstrate efficient laser-induced fluorescence (LIF) at 420 nm — corresponding to the Rb $6P_{3/2}\to 5S_{1/2}$ transition — induced by 780 nm or 795 nm laser radiation, which is nearly resonant via a two-photon excitation pathway involving the $5S_{1/2}\to 5D_{3/2}$ transition. We use a 1-cm-long T-shaped all-sapphire cells containing Rb vapor and different pressures of Ne buffer gas. The dependence of 420 nm LIF intensity on temperature, buffer gas pressure, and excitation wavelength is analyzed. The optimal conditions for achieving bright blue-violet emission are established. Practical applications of this up-conversion process are discussed. The results demonstrate the potential for using Rb vapor cells as compact and efficient optical up-conversion filters, converting near-infrared laser radiation into visible blue emission.