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A bright source of fiber-coupled, polarized single photons is an essential component of any realistic quantum network based on today's existing fiber infrastructure. Here, we develop a Purcell-enhanced, polarized source of single photons at room temperature by coupling single colloidal quantum dots to the localized surface plasmon-polariton modes of single gold nanorods, combined on the surface of an optical nanofiber. A maximum enhancement of the photon emission rate of 62 times was measured corresponding to a degree of polarization of 85%, and a brightness enhancement of four times in the fiber mode. Evanescent coupling of photons to the nanofiber guided modes ensures automatic coupling to a single mode fiber. Our technique opens the way to realizing bright sources of polarized single photons connected to fiber networks using a simple composite technique.

We demonstrate the use of laser-induced phase gratings to control the emission characteristics of self-assembled semiconductor quantum dots. The microscopic Coulomb interaction between the photoinduced charge densities in a dot, referred to as the local field effect, affects the macroscopic optical properties of a dot ensemble even with inhomogeneous broadening, and forms a phase grating by spatially modulating the exciton resonant frequency. In the low excitation regime, the diffracted light intensity (observed using photon echoes) gradually rose with time delay--a result very different from the conventional instantaneous response to pulse excitation. With increasing excitation intensity, the response of the diffracted signal became more immediate and exhibited a biexponential decay. The change in the temporal profile can be systematically explained by analyzing the dynamics of the phase grating. Our findings suggest an optical switching mechanism using this intrinsic property of semiconductor quantum dots. [ABSTRACT FROM AUTHOR]

We studied the population and coherence dynamics of a biexciton in a planar CuCl microcavity. We developed a time-resolved two-photon polarization spectroscopy technique, by which we extracted the population dynamics of the biexciton even when the biexciton was spectrally overlapped with the lower cavity polariton. The observed lifetime of the cavity biexciton in the weak-coupling regime was much shorter than that of a bare CuCl thin film without a cavity, which directly demonstrates cavity enhancement of the radiative decay rate of the biexciton. The cavity enhancement originates from the hybridization of the unbound two-cavity-polariton state to the biexciton wave function by the biexciton-cavity coupling. By comparing the population and coherence decay curves of the biexciton, we found that the coherence of the cavity biexciton was limited by the radiative population decay. [ABSTRACT FROM AUTHOR]