Carrier lifetime assessment in integrated Ge waveguide devices

Carrier lifetimes in Ge waveguides on Si are deduced from time-resolved pump-probe spectroscopy. For a 1 pm wide Ge waveguide, a lifetime of 1.6 ns is estimated for a carrier density of around 2 x10(19) cm(-3)

Extraction of carrier lifetime in Ge waveguides using pump probe spectroscopy

Carrier lifetimes in Ge-on-Si waveguides are deduced using time-resolved infrared transmission pump-probe spectroscopy. Dynamics of pump-induced excess carriers generated in waveguides with varying Ge thickness and width is probed using a CW laser. The lifetimes of these excess carriers strongly depend on the thickness and width of the waveguide due to defect assisted surface recombination. Interface recombination velocities of 0.975 x 10(4) cm/s and 1.45 x 10(4) cm/s were extracted for the Ge/Si and the Ge/SiO2 interfaces, respectively. Published by AIP Publishing

Experimental demonstration of evanescent coupling from optical fibre tapers to photonic crystal waveguides

Experimental results demonstrating nearly complete mode-selective evanescent coupling to a photonic crystal waveguide from an optical fibre taper are presented. Codirectional coupling with 98% maximum power transfer to a photonic crystal waveguide of length 65 μm and with a coupling bandwidth of 20 nm is realised

50GHz Ge waveguide electro-absorption modulator integrated in a 220nm SOI photonics platform

We report waveguide-integrated Ge electro-absorption modulators operating at 1615nm wavelength with 3dB bandwidth beyond 50GHz and a capacitance of 10fF, A 2V voltage swing enables 4.6dB DC extinction ratio for 4.1dB insertion loss

Flux Expulsion - Field Evolution in Neutron Stars

Models for the evolution of magnetic fields of neutron stars are constructed, assuming the field is embedded in the proton superconducting core of the star. The rate of expulsion of the magnetic flux out of the core, or equivalently the velocity of outward motion of flux-carrying proton-vortices is determined from a solution of the Magnus equation of motion for these vortices. A force due to the pinning interaction between the proton-vortices and the neutron-superfluid vortices is also taken into account in addition to the other more conventional forces acting on the proton-vortices. Alternative models for the field evolution are considered based on the different possibilities discussed for the effective values of the various forces. The coupled spin and magnetic evolution of single pulsars as well as those processed in low-mass binary systems are computed, for each of the models. The predicted lifetimes of active pulsars, field strengths of the very old neutron stars, and distribution of the magnetic fields versus orbital periods in low-mass binary pulsars are used to test the adopted field decay models. Contrary to the earlier claims, the buoyancy is argued to be the dominant driving cause of the flux expulsion, for the single as well as the binary neutron stars. However, the pinning is also found to play a crucial role which is necessary to account for the observed low field binary and millisecond pulsars.Comment: 23 pages, + 7 figures, accepted for publication in Ap

Fouling of Some Canadian Crude Oils

A thermal fouling study was undertaken using three sour Canadian crude oils. Experiments were carried out in a re-circulation fouling loop, equipped with an annular (HTRI) electrically heated probe. Fluids at pressures of about 1000-1340 kPa under a nitrogen atmosphere were re-circulated at a velocity of 0.75 m/s for periods of 48 hours, and the decline in heat transfer coefficient followed under conditions of constant heat flux. Bulk temperatures were varied over the range 200-285°C, and initial surface temperatures from 300 to 380°C. Heat fluxes were in the range of 265-485 kW/m2

Linear and nonlinear optical spectroscopy of a strongly-coupled microdisk-quantum dot system

A fiber taper waveguide is used to perform direct optical spectroscopy of a microdisk-quantum-dot system, exciting the system through the photonic (light) channel rather than the excitonic (matter) channel. Strong coupling, the regime of coherent quantum interactions, is demonstrated through observation of vacuum Rabi splitting in the transmitted and reflected signals from the cavity. The fiber coupling method also allows the examination of the system's steady-state nonlinear properties, where saturation of the cavity-QD response is observed for less than one intracavity photon.Comment: adjusted references, added minor clarification

Electrostatic actuators for misalignment compensation in multi-layered microsystem devices

AbstractElectrostatic actuation is a promising approach to compensate for misalignment of bonded, multi-layered microsystem devices. The present work discusses the performance of electrostatic actuators used for in-plane misalignment compensation in an atom chip comprising an optical cavity. Experimental investigation revealed that the central frame suspending the mirrors can be moved between 3-5 m in the in-plane direction for the applied DC voltage of 90 volts. Future work involves characterizing the mirror displacement for optical tuning function