Helmut Ritsch

An array of closely spaced, dipole coupled quantum emitters exhibits collective energy shifts as well as super- and subradiance with characteristic tailorable spatial radiation patterns. Ring shape configurations exhibit exponential suppression of spontaneous emission and lossless excitation transport. Optimizing the geometry with respect to the spatial profile of a near resonant optical structures allows to increase the ratio between light scattering into the cavity mode and free space by orders of magnitude. This comes with very distinct nonlinear particle number scaling for the strength of coherent light-matter interactions versus collective decay. In particular, for subradiant states the collective cooperativity increases much faster than the linear ~N dependence of independent emitters in the low excitation regime. This extraordinary collective enhancement is manifested both, in the intensity and phase profile of the sharp collective emitter anti-resonances detectable at the cavity output port via transmission spectroscopy. Subradiant atomic excitations show a much larger effective cooperativity than superradiant states.

References:

Plankensteiner, David, et al. "Cavity antiresonance spectroscopy of dipole coupled subradiant arrays." Physical review letters 119.9 (2017): 093601,

M Moreno-Cardoner, et. Al. “Extraordinary subradiance with lossless excitation transfer in dipole-coupled nano-rings of quantum emitters” arXiv preprint arXiv:1901.10598, 2019.