Ultrastrong Light–Matter Coupling in Deeply Subwavelength THz LC Resonators

• DOI: 10.1021/acsphotonics.8b01778
• Publication Date: 2019-04-02T16:40:44Z
• Authors: Mathieu Jeannin; Giacomo Mariotti ...; Stéphan Suffit; Djamal Gacemi; Angela Vasanelli; Lianhe Li; Alexander Giles D...; Edmund Linfield; Carlo Sirtori; Yanko Todorov
• Keywords: [PHYS.PHYS.PHYS-OPTICS] Physics [physics]/Physics [physics]/Optics [physics.optics]; [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics]; Quantum Physics; Condensed Matter - Mesoscale and Nanoscale Physics; FOS: Physical sciences; 02 engineering and technology; 7. Clean energy; [PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph]; [PHYS.COND.CM-GEN] Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other]; Quantum Gases (cond-mat.quant-gas); [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other]; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Condensed Matter - Quantum Gases; Quantum Physics (quant-ph); 0210 nano-technology; [PHYS.QPHY] Physics [physics]/Quantum Physics [quant-ph]

The ultra-strong light-matter coupling regime has been demonstrated in a novel three-dimensional inductor-capacitor (LC) circuit resonator, embedding a semiconductor two-dimensional electron gas in the capacitive part. The fundamental resonance of the LC circuit interacts with the intersubband plasmon excitation of the electron gas at $��_c = 3.3$~THz with a normalized coupling strength $2��_R/��_c = 0.27$. Light matter interaction is driven by the quasi-static electric field in the capacitors, and takes place in a highly subwavelength effective volume $V_{\mathrm{eff}} = 10^{-6}��_0^3$ . This enables the observation of the ultra-strong light-matter coupling with $2.4\times10^3$ electrons only. Notably, our fabrication protocol can be applied to the integration of a semiconductor region into arbitrary nano-engineered three dimensional meta-atoms. This circuit architecture can be considered the building block of metamaterials for ultra-low dark current detectors.