Collimated UV light generation by two-photon excitation to a Rydberg state in Rb vapor

摘要

We use two continuous-wave laser beams of 780 nm and 515 nm to optically drive Rb-85 atoms in a heated vapor cell to a low-lying Rydberg state 10D(5/2). We observe a collimated ultraviolet (UV) beam at 311 nm, corresponding to the transition frequency from the 11P(3/2) state to the 5S(1/2) state. This indicates the presence of a coherent four-wave mixing process, built up by two input laser fields as well as terahertz (THz) radiation of 3.28 THz, which is generated by amplified spontaneous emission between the 10D(5/2) and 11P(3/2) states. We characterize the 311 nm UV light generation and its dependence on various physical parameters. This scheme could open up a new possibility for generating narrow-band THz waves as well as deep UV radiation. (C) 2019 Optical Society of America