Optical cavity for enhanced parametric four-wave mixing in rubidium

TL;DR

This paper demonstrates a ring cavity that significantly enhances four-wave mixing efficiency in rubidium, resulting in a 50-fold increase in blue light output and improved spatial quality, advancing its potential for future applications.

Contribution

The implementation of a ring cavity with high finesse to boost four-wave mixing efficiency in rubidium is a novel approach that substantially increases output power and improves beam quality.

Findings

Circulating intensity increased by a factor of 5.6

Generated power at 420 nm reached 1.9 mW, 50 times previous results

Output shows improved spatial quality and potential saturation effects

Abstract

We demonstrate the implementation of a ring cavity to enhance the efficiency of parametric four-wave mixing in rubidium. Using an input coupler with 95% reflectance, a finesse of 19.6$\pm$0.5 is achieved with a rubidium cell inside. This increases the circulating intensity by a factor of 5.6$\pm$0.5, and through two-photon excitation on the $5s_{1/2}\rightarrow5d_{5/2}$ transition with a single excitation laser, up to 1.9$\pm$0.3 mW of power at 420 nm is generated, 50 times what was previously generated with this scheme. The dependence of the output on Rb density and input power has been explored, suggesting the process may be approaching saturation. The blue output of the cavity also shows greatly improved spatial quality, combining to make this a promising source of 420 nm light for future experiments.