Externally Mode-Matched Cavity Quantum Electrodynamics with Charge-Tunable Quantum Dots

We present coherent reflection spectroscopy on a charge and dc Stark tunable quantum dot embedded in a high-quality and externally mode-matched microcavity. The addition of an exciton to a single-electron-charged quantum dot forms a trion that interacts with the microcavity just below the strong-coupling regime of cavity quantum electrodynamics. Such an integrated, monolithic system is a crucial step towards the implementation of scalable hybrid quantum-information schemes that are based on an efficient interaction between a single photon and a confined electron spin.

Figure 1

(a) Schematic of the scalable cavity QED system based on electrically gated QDs embedded in oxide-apertured micropillars. (b) Two-dimensional reflectivity scan of a micropillar cavity taken with a laser resonant with the cavity mode. The mode in the center can be seen clearly as a dip in the reflected signal. (c) Higher resolution reflectivity scan taken in a $10\mu \mathrm{m}\times 10\mu \mathrm{m}$ area containing the mode.

Figure 2

(a) Photoluminescence spectra as a function of applied bias for a QD in the mirror region at 4 K. (b) Emission decay traces for 10 QDs in the mirror region. Straight traces are taken with 18.5 V applied bias ($X^{-}$) and dashed traces are taken with 17.5 V applied bias ($X^0$). (c) Emission decay traces for QDs on resonance with cavity modes for several different cavities. The straight (dashed) traces correspond to an $X^{-}$ ($X^0$) decay. (d) $g^{(2)}(\tau )$ measurements for an $X^{-}$ (straight) and $X^0$ (dashed) transition.

Figure 3

(a) Cavity reflection spectrum of an unloaded micropillar cavity measured by recording the reflected signal of a tunable-wavelength laser. Equation (1) with $g=0$ plus a linear background is used to fit the data. (b) Cavity reflection spectrum of a QD coupled to the micropillar cavity in (a). Eq. (1) plus a linear background is used to fit the data.

Figure 4

(a) Microphotoluminescence spectra of nondegenerate optical modes in a micropillar. H (V) polarized modes are black (grey). Inset: SEM image of a micropillar. (b) Photoluminescence spectra as a function of applied bias for two QDs (labeled QD of interest and reference QD) and two nondegenerate fundamental cavity modes (labeled H mode and V mode). (c) Lifetime traces for a few bias settings; 7.62, 8.2, 8.86, and 9.5 V. (d) Deconvolved lifetimes as a function of emission energy with fit.