Progress to reduce nonradiative Auger decay in colloidal nanocrystals has recently been made by growing thick shells. However, the physics of Auger suppression is not yet fully understood. Here, we examine the dynamics and spectral characteristics of single CdSe-dot-in-CdS-rod nanocrystals. These exhibit blinking due to charging/discharging, as well as trap-related blinking. We show that one-dimensional electron delocalization into the rod-shaped shell can be as effective as a thick spherical shell at reducing Auger recombination of the negative trion state.

We explore the electrodynamic coupling between a plane wave and an infinite two-dimensional periodic lattice of magnetoelectric point scatterers, deriving a semianalytical theory with consistent treatment of radiation damping, retardation, and energy conservation. We apply the theory to arrays of split ring resonators and provide a quantitative comparison of measured and calculated transmission spectra at normal incidence as a function of lattice density, showing excellent agreement. We further show angle-dependent transmission calculations for circularly polarized light and compare with the angle-dependent response of a single split ring resonator, revealing the importance of cross coupling between electric dipoles and magnetic dipoles for quantifying the pseudochiral response under oblique incidence of split ring lattices.

Passive photonic crystals have been shown to exhibit a multitude of interesting phenomena, including slow-light propagation in line-defect waveguides. It was suggested that by incorporating an active material in the waveguide, slow light could be used to enhance the effective gain of the material, which would have interesting application prospects, for example enabling ultra-compact optical amplifiers for integration in photonic chips. Here we experimentally investigate the gain of a photonic crystal membrane structure with embedded quantum wells. We find that by solely changing the photonic crystal structural parameters, the maximum value of the gain coefficient can be increased compared with a ridge waveguide structure and at the same time the spectral position of the peak gain be controlled. The experimental results are in qualitative agreement with theory and show that gain values similar to those realized in state-of-the-art semiconductor optical amplifiers should be attainable in compact photonic integrated amplifiers.

We give an overview of slow-and fast-light effects in semiconductor active waveguides. Experimental and theoretical results are presented, emphasizing the physics of these phenomena and the limitations imposed by the carrier dynamical processes.A train of optical pulses injected into a quantum dot semiconductor optical waveguide, where the velocity is slowed down and the pulsewidth is reduced.

We demonstrate that a simple silver coated ball lens can be used to accurately measure the entire distribution of radiative transition rates of quantum dot nanocrystals. This simple and cost-effective implementation of Drexhage's method that uses nanometer-controlled optical mode density variations near a mirror, not only allows an extraction of calibrated ensemble-averaged rates, but for the first time also to quantify the full inhomogeneous dispersion of radiative and non radiative decay rates across thousands of nanocrystals. We apply the technique to novel ultrastable CdSe/CdS dot-in-rod emitters. The emitters are of large current interest due to their improved stability and reduced blinking. We retrieve a room-temperature ensemble average quantum efficiency of 0.87 ± 0.08 at a mean lifetime around 20 ns. We confirm a log-normal distribution of decay rates as often assumed in literature, and we show that the rate distribution-width, that amounts to about 30% of the mean decay rate, is strongly dependent on the local density of optical states.

We present a semianalytical point-dipole method that uses Ewald lattice summation to find the dispersion relation of guided plasmonic and bianisotropic modes in metasurfaces composed of two-dimensional (2D) periodic lattices of arbitrarily strongly scattering magnetoelectric dipole scatterers. This method takes into account all retarded electrodynamic interactions as well as radiation damping self-consistently. As illustration, we analyze the dispersion of plasmon nanorod lattices, and of 2D split ring resonator lattices. Plasmon nanorod lattices support transverse and longitudinal in-plane electric modes. Scatterers that have an in-plane electric and out-of-plane magnetic polarizability, but without intrinsic magnetoelectric coupling, result in two bands that are mixtures of the bands of electric-only and magnetic-only lattices. Thereby, bianisotropy through mutual coupling, in absence of building-block bianisotropy, is evident. Once strong bianisotropy is included in each building block, the Bloch modes become even more strongly magnetoelectric. Our results are important to understand spatial dispersion and bianisotropy of metasurface and metamaterial designs.

A two-photon mechanism for cooling atoms below the Doppler temperature is analyzed. We consider the magnesium ladder system (3s(2))S-1(0)->(3s3p)P-1(1) at 285.2 nm followed by the (3s3p)P-1(1)->(3s3d)D-1(2) transition at 880.7 nm. For the ladder system quantum coherence effects may become important. Combined with the basic two-level Doppler cooling process this allows for reduction of the atomic sample temperature by more than a factor of 10 over a broad frequency range. First experimental evidence for the two-photon cooling process is presented and compared to model calculations. Agreement between theory and experiment is excellent. In addition, by properly choosing the Rabi frequencies of the two optical transitions a velocity independent atomic dark state is observed

We present pump-probe measurements of an all-optical photonic crystal switch based on a nanocavity, resolving fast coherent temporal dynamics. The measurements demonstrate the importance of coherent effects typically neglected when considering nanocavity dynamics. In particular, we report the observation of an idler pulse. The measurements are in good agreement with a theoretical model that allows us to ascribe the observation to oscillations of the free carrier population in the nanocavity. The effect opens perspectives for the realization of new all-optical photonic crystal switches with unprecedented switching contrast.PACS numbers: 42.65. Pc, 42.65.Hw, 42.79.Ta, 78.67.Pt Keywords: Photonic Crystal, Nonlinear optics, Cavity, All-optical switching, Parametric gain, Temporal characterization Over the last decade there has been significant progress in integrated optics in terms of decreasing both footprint and energy consumption. Photonic solutions are thus increasingly becoming a credible alternative to electrical signal processing. The control of light with highly efficient all-optical functions, such as active switching/gating operations or the use of integrated add/drop channels, is of utmost importance. In order to cope with the constraints related to the dense integration of numerous all-optical functions on a single integrated photonic chip (IPC), the total energy consumption devoted to each individual function must be of the order of a few fJ/bit [1]. Planar photonic crystal (PhC) cavities are promising candidates for the realization of all-optical switching operations thanks to their small volume, high quality factor, and compatibility with complementary metal-oxidesemiconductor (CMOS) technology [2][3][4][5][6][7]. In particular, the report of 10 dB switching contrast with a record low operating energy of 2.88 fJ/bit is noteworthy [7].Classical schemes for all-optical switching using a PhC cavity involve the dynamical control of the cavity resonance via a pump pulse [2,8,9], which shifts the cavity's resonance, thus controlling the transmission of a subsequent probe (see Fig. 1b)). The cavity resonance can be changed either by the Kerr effect [10], or through the dispersion caused by free carriers (FCD) [11] generated by the absorption of the pump. The latter process is usually preferred as it has the advantage of building up over time and therefore requires less pump power. Thus far, the lowest switching energy was obtained by taking advantage of a combination of linear absorption and nonlinear two-photon absorption (TPA) [7,12] in a configuration that benefits from the band filling dispersion. The band filling dispersion adds up to the free carriers dispersion (FCD) to give rise to a stronger resonance shift [13]. However these demonstrations require complex material engineering, and showed limitations in terms of switching speed due to a long free carrier lifetime. In particular, a long carrier lifetime gives rise to strong patterning effects when operated at a high rate [5,14]. The use of a small c...