Quantum dot photonic crystal nanocavities: Transition from weak to strong coupling and nonlinear emissions

Abstract

Photonic crystal slab nanocavities containing one layer of quantum dots have exhibited: strong coupling to a single quantum dot; tuning by condensation of xenon gas; linewidth broadening due to ensemble dot absorption; gain and lasing. Over a year ago, vacuum Rabi splitting was achieved between an InAs single quantum dot and a photonic crystal slab nanocavity [1]. Since then we have observed such anticrossings in many different nanocavities, and nonlinear emission experiments have been performed with nonresonant excitation and begun with resonant excitation.We report tuning such a nanocavity by as much as 5 nm by the condensation of Xe gas onto the slab and into the photonic crystal holes [2]. Compared with temperature scanning, it has an eight times larger scan range and avoids phonon broadening. This new method is a great improvement in the search for the two accidental coincidences (dot spatially in a field antinode with a spectral transition frequency degenerate with the cavity mode) essential for cavity QED and strong coupling experiments. ling anti-crossings using Xe condensation to scan. (a) PL spectra at 25 K with low-pow Emission linewidths of quantum dot (QD) photonic-crystal-slab nanocavities are measured as a function of lin temperature and fabrication parameters with low-and high-power, cw and pulsed, nonresonant excitation [3]. The cavity linewidth is dominated by the absorption of the ensemble of QDs having a density of # 400/Pm 2 ; above the absorption edge the cavity linewidth broadens considerably compared with the empty cavity ewidth as shown in Fig. 2(b&c). Such a high QD density was necessary to have any hope of finding the two accidental coincidences. The greater scan range provided by xenon condensation should permit the dot density to be lowered by a factor of four or five in future experiments, thereby reducing the ensemble absorption and cavity linewidth.