High Q and sub-wavelength THz electric field confinement in ultrastrongly coupled THz resonators

We report on hybrid THz cavities based on ultrastrong coupling between a Tamm cavity and an LC circuit metamaterial and demonstrate that these hybrid THz cavities combine high quality factors of up to Q∼37 with a deep-subwavelength mode volume of V=3.2x10−4λ3. These Tamm cavity-LC metamaterial coupled resonators open a route toward the development of single photon THz emitters and detectors and to the exploration of ultrastrong THz light–matter coupling with a high degree of coherence in the few to single electron limit.