Cavity Quantum Electrodynamics Using Single Quantum Dot
Takehiko Tawara, Hidehiko Kamada, and Stephen Hughes*
Optical Science Laboratory, *Queen’s University
Cavity quantum electrodynamics (cQED) has been intensively studied using a solid-state two-level system, and has found use for quantum information devices such as those employing nonlinearities generated by single photons and the quantum state exchange between light and matter. In solid-state cQED, however, the environment that surrounds a two-level system is quite different from that of an atom trapped in a vacuum, and so the interpretation of its optical response is abstruse . In this study, we explore a novel optical response in solid-state cQED in weak and strong coupling regimes, and investigate the corresponding mechanisms.
We used a self-assembled semiconductor quantum dot (QD) as a two-level system that is embedded in a 2D photonic crystal nanocavity. Figure 1 shows a series of PL spectra of a QD exciton (X) and the cavity mode (C) in a weak coupling regime. As the temperature increases, these two peaks experience a continuous redshift thereby reducing the relative energy separation. However, surprisingly, as the two peaks approach one another near the crossover, the cavity modes clearly undergo a blueshift toward the exciton resonance (mode attraction) . In contrast, the PL spectrum in a strong coupling regime exhibits Rabi splitting with anti-crossing dispersion (Fig. 2). When the excitation power is increased, we observe that the Rabi splitting vanishes although anti-crossing is maintained. We analyzed both curious phenomena theoretically in weak and strong coupling regimes. As the result, we proved that these peculiar phenomena in solid-state cQED arise from the large exciton dephasing and the optical radiation characteristics of a 2D photonic crystal cavity .
This work was partially supported by the Strategic Information and Communications R&D Promotion Programme (SCOPE) of Japan.
 For example, K. Hennessy et al., Nature 445 (2007) 896.
 T. Tawara et al., Opt. Express 18 (2010) 2719.
 S. Hughes et al., Opt. Express 17 (2009) 3322.
Fig. 1. Series of PL spectra as a function of
temperature in weak coupling regime.
Fig. 2. PL color map and PL spectra at zero
detuning with various excitation powers
in strong coupling regime.
[back] [Top] [Next]