Chip Scale Emission of Blue Light at Elevated Temperatures in Optical Waveguides Integrated With Rubidium Vapor

ABSTRACT Blue light emission from Rubidium (Rb) vapor cells is attractive for a myriad of applications, from quantum sensing and metrology to communication, quantum memories, and more. Typically, such emissions are observed from bulky free‐space glass cells. Here we experimentally demonstrate the generation of blue light from a chip‐scale optical waveguide integrated with rubidium vapor. The atomic ladder excitation using a combination of 780 and 776 nm light propagates through the Atomic Clad Waveguide (ACWG), directly interacting with Rubidium, emitting a photon at 420 nm and a matching photon at 5233 nm. The blue light emission is characterized and measured at elevated temperatures, up to 240°C. The results show a peculiar dependency of emission intensity as a function of temperature, wherein the emission intensity monotonically increases up to 200°C, followed by a pronounced roll‐off at higher temperatures. This is explained by a model that considers the reabsorption of emitted blue photons propagating along the optically thick Rubidium vapor. These results demonstrate a viable pathway for integrating nonlinear atomic vapor processes into chip‐scale quantum devices.