Abstract-Terahertz-driven phase transition applied as a room-temperature terahertz detector

Christopher G. Wade, Matteo Marcuzzi, Emanuele Levi, Jorge M. Kondo, Igor Lesanovsky, Charles S. Adams, Kevin J. Weatherill

(Submitted on 1 Sep 2017)

https://arxiv.org/abs/1709.00262

There are few demonstrated examples of phase transitions that may be driven directly by terahertz-frequency electric fields, and those that are known require field strengths exceeding 1 MVcm−1. Here we report a room-temperature phase transition driven by a weak (≪1 Vcm−1), continuous-wave terahertz electric field. The system consists of caesium vapour under continuous optical excitation to a high-lying Rydberg state, which is resonantly coupled to a nearby level by the terahertz electric field. We use a simple model to understand the underlying physical behaviour, and we demonstrate two protocols to exploit the phase transition as a narrowband terahertz detector: the first with a fast (20 μs) nonlinear response to nano-Watts of incident radiation, and the second with a linearised response and effective noise equivalent power (NEP) ≤1pWHz−1/2. The work opens the door to a new class of terahertz devices controlled with low field intensities and operating around room temperature