Abstract

We use two continuous-wave laser beams of 780 nm and 515 nm to optically drive ${}^{85}\mathrm{Rb}$ atoms in a heated vapor cell to a low-lying Rydberg state $10{\mathrm{D}}_{5/2}$. We observe a collimated ultraviolet (UV) beam at 311 nm, corresponding to the transition frequency from the $11{\mathrm{P}}_{3/2}$ state to the $5{\mathrm{S}}_{1/2}$ 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 $10{\mathrm{D}}_{5/2}$ and $11{\mathrm{P}}_{3/2}$ 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.

© 2019 Optical Society of America

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