Tuning and Switching a Plasmonic Quantum Dot Sandwich in a Nematic Line Defect

We study the quantum-mechanical effects arising in a single semiconductor core/shell quantum dot controllably sandwiched between two plasmonic nanorods. Control over the position and the sandwich confinement structure is achieved by the use of a linear-trap, liquid-crystal line defect and laser tweezers that push the sandwich together. This arrangement allows for the study of exciton plasmon interactions in a single structure, unaltered by ensemble effects or the complexity of dielectric interfaces. We demonstrate the effect of plasmonic confinement on the photon-antibunching behavior of the quantum dot and its luminescence lifetime. The quantum dot behaves as a single emitter when nanorods are far away from the quantum dot but shows possible multiexciton emission and a significantly decreased lifetime when tightly confined in a plasmonic sandwich. These findings demonstrate that liquid crystal defects, combined with laser tweezers, enable a versatile platform to study plasmonic coupling phenomena in a nanoscale laboratory, where all elements can be arranged almost at will.Comment: Supporting information at the en

Liquid Crystalline Order and Electric Switching of Upconversion Luminescence in Colloidal Nanorod Suspensions

International audienceThe polarization‐dependent photon upconversion luminescence properties of large‐scale orientationally ordered soft matter systems formed by colloidal nanorods dispersed in an isotropic solvent are studied. The electrostatically charged photon‐upconverting nanorods form an isotropic dispersion at low concentrations, whereas orientational order and a nematic phase emerge at high concentrations. When an alternating electric field is applied, particles align in the direction of the electric field in both nematic and isotropic phases, though the nature of this electric switching is different in these two phases. Owing to the long‐range orientational order in the nematic phase, the upconversion luminescence from the particles is polarized without an external field. Polarization dependence of these properties can also be electrically induced in an isotropic phase of the colloidal nanorods. Further, the dynamics of switching of photon upconversion luminescence in both nematic and isotropic dispersions are explored and their potential technological uses are dicussed

System-Level Simulator for the W-CDMA Low Chip Rate TDD System Ý

Abstract — A system-level simulator for the W-CDMA Low Chip Rate TDD system is developed. This simulator considers multi-cell and multi-user environmets and SIR-based power control. For accurate and reliable results, inner-cell and outer-cell interference is modeled by chip-level spreading and an SIR estimation scheme is used. From this simulator, system-level performance is evaluated in terms of the received SIR distributions for downlink and uplink. The degradation probability is also introduced as a QoS indicator in system-level. I