Terahertz electrometry via infrared spectroscopy of atomic vapor [dataset]

In recent years, the characterisation of radiation falling within the so-called ‘terahertz (THz) gap’ has become an ever more prominent issue due to the increasing use of THz systems in applications such as nondestructive testing, security screening, telecommunications and medical diagnostics. THz detection technologies have advanced rapidly, yet traceable calibration of THz radiation remains challenging. In this paper, we demonstrate a system of electrometry in which a THz signal can be characterized using laser spectroscopy of highly excited (Rydberg) atomic states. We report on proof-of-principle measure- ments that reveal a minimum detectable THz electric field amplitude of 1.07±0.06 V/m at 1.06 THz (3 ms detection), corresponding to a THz power at the atomic cell of approximately 3.4 nW. Due to the relative simplicity and cryogen-free nature of this system, it has the potential to provide a route to a SI traceable ‘atomic candle’ for THz calibration across the terahertz frequency range, and provide an alternative to calorimetric methods.