Directional THz generation in hot Rb vapor excited to a Rydberg state

TL;DR

This paper demonstrates directional terahertz and ultraviolet light generation in heated rubidium vapor excited to a Rydberg state, revealing conditions for efficient high-power narrow-band THz emission.

Contribution

It introduces a novel method for generating directional THz radiation using Rydberg states in heated rubidium vapor, with detailed characterization of the process.

Findings

Directional THz beams at 3.3 THz and 7.8 THz observed.

Optimal conditions identified for THz and UV generation.

Potential for high-power narrow-band THz radiation established.

Abstract

We optically excite $^{85}$Rb atoms in a heated vapor cell to a low-lying Rydberg state 10D$_{5/2}$ and observe directional terahertz (THz) beams at 3.3 THz and 7.8 THz. These THz fields are generated by amplified spontaneous emission from the 10D$_{5/2}$ state to the 11P$_{3/2}$ and 8F$_{7/2}$ states, respectively. In addition, we observe ultraviolet (UV) light produced by four-wave mixing of optical pump lasers and the 3.3 THz field. We characterize the generated THz power over the detuning and power of pump lasers, and identify experimental conditions favoring THz and UV generation, respectively. Our scheme paves a new pathway towards generating high-power narrow-band THz radiation.