Electromechanical tuning of double-membrane Photonic Crystal Cavities
PL spectra and peak shift obtained by applying a gradually increasing voltage are shown in Fig. 1b. We report up to 7 nm mode shift when the applied bias reaches 8.6 V. By further increasing the voltage we observe the well-known pull-in phenomenon: the cantilever collapses on the substrate because electrostatic forces win over elastic forces. We attribute the need for high voltages to fabrication issues and imperfections such as the complete erosion of the p-doped InGaAsP layer in the photonic crystal region during the sacrificial layer etching. Further process optimization should result in PCCs with Q factors>10'000, electromechanically tunable over >30 nm.
Photonic Integrated Circuits operating at the Single-Photon Level
We present an approach to the full integration of active and passive single-photon devices on a single chip. Single-photon sources coupled to waveguides are realized by embedding InAs quantum dots (QDs) in photonic crystal (PhC) cavities. In order to control the QD-cavity coupling, devices for the electrical control of both the exciton energy and the cavity resonant wavelength are demonstrated. A waveguide single-photon detector is obtained by patterning superconducting NbN nanowires on top of the ridge waveguides, resulting in high efficiency and low jitter. This set of technologies opens the way to fully integrated quantum photonic circuits for quantum information processing based on photonic qubits.
Correlations for mass transfer between fluidized spheres and a liquid
Abstract Data on mass transfer between the solid particles and the liquid in a fluidized bed have been analyzed. After a convenient selection, various correlations have been derived. They show that for a given fluidized system, the Sherwood number is independent on the Reynolds number.