THz ultrastrong light-matter coupling

Cavity photon resonators with ultrastrong light-matter interactions are attracting interest both in semiconductor and superconducting systems displaying the capability to manipulate the cavity quantum electrodynamic ground state with controllable physical properties. Here we review a series of experiments aimed at probing the ultrastrong light-matter coupling regime, where the vacuum Rabi splitting Ohm is comparable to the bare transition frequency ??. We present a new platform where the inter-Landau level transition of a two-dimensional electron gas (2DEG) is strongly coupled to the fundamental mode of deeply subwavelength split-ring resonators operating in the mm-wave range. Record-high values of the normalized light-matter coupling ratio = 0.87 are reached and the system appears highly scalable far into the microwave range. THz ulTrasTrong ligHT-maTTer coupling. Available from: https://www.researchgate.net/publication/281289094_THz_ulTrasTrong_ligHT-maTTer_coupling [accessed Nov 20, 2015].