Omnidirectional Inter-Satellite Optical Communicator (ISOC)

The objective of the Omnidirectional Inter-Satellite Optical Communicator (ISOC) project is to design a compact, lightweight,and energy efficient communicator module for use between satellites in space. This module will achieve continuous optical communication, with simultaneous data transmission and reception, at up to1 gigabit per second (Gbits) data rates for small spacecraft separated by up to 200 kilometers (kms). To achieve this goal,a data communicator with full spherical coverage field of view (FOV) needs to be designed. The proposed ISOC is a dodecahedron geometric array of chipscale, microelectromechanical systems (MEMS) based gimbal-less scanning mirrors that provide adjustable beam pointing and spherical FOV coverage for uninterrupted data transmission between several small spacecraft at arbitrary relative positions. This design eliminates known pointing issues and hence allows accurate direction of arrival calculations.Moreover, the proposed approach will enable data relaying between multiple satellites, and enable relative navigation control

Radiation properties of an integrated optical leaky wave antenna with periodic silicon perturbations

We propose a highly directive optical leaky wave antenna (OLWA) radiating at 1550 nm composed of a dielectric waveguide comprising periodic silicon (Si) perturbations. The antenna working principle is based on the excitation of a leaky wave guided mode in the perturbed waveguide. Here we study the radiation properties for two sets of perturbation dimensions, and show beam scanning capabilities of the antenna (radiation level and direction) at broadside by varying the free space wavelength. Moreover, the use of Si offers the electronic/optical tunability of its complex refractive index by excess electron-hole carrier density generation via current injection (electronic control) or optical absorption (optical control). Therefore, by changing the Si refractive index we vary the leaky wave attenuation constant and the input impedance of the antenna, which in turn allow for beam control capabilities. © 2012 IEEE

Room-temperature direct bandgap electroluminesence from Ge-on-Si light-emitting diodes

We report what we believe to be the first demonstration of direct bandgap electroluminescence (EL) from Ge/Si heterojunction light-emitting diodes (LEDs) at room temperature. In-plane biaxial tensile strain is used to engineer the band structure of Ge to enhance the direct gap luminescence efficiency by increasing the injected electron population in the direct Γ valley. Room-temperature EL is observed at the direct gap energy from a Ge/Si p-i-n diode exhibiting the same characteristics of the direct gap photoluminescence of Ge. The integral direct gap EL intensity increases superlinearly with electrical current owing to an indirect valley filling effect. These results indicate a promising future of tensile-strained Ge-on-Si for electrically pumped, monolithically integrated light emitters on Si

Structural and Superconductivity Properties of BaFe2-xPtxAs2

Extraordinary magnetic behaviors, resistivity properties, and lattice parameters of the main sample BaFe2As2 and BaFe2-xPtxAs2 in the variation of x from 0 to 0.4 with the step of 0.1 were investigated. The bulk materials have been prepared by the solid-state reaction method and sealed into a quartz tube. The crystal structure of all samples exhibited the ThCr2Si2-type crystal structure which is in harmony with earlier studies in the literature. The superconducting states with magnetization measurements have been detailed in the wide temperature range 5-170 K, up to a field of 20 Oe. Increasing Pt and decreasing Fe elements in the BaFe2-xPtxAs2 compound deteriorated superconductivity. Using magnetization measurement data, we present the variation of superconducting critical temperature (T-c) correlating with a Pt dopant rate from x = 0 to x = 0.4. The dopant rate of x = 0.3 exhibited the limit rate for maximum Tc; deterioration of superconductivity was revealed with a dopant rate of more than x = 0.3. This should be explained by varying Tc related to a lattice shrinking and pressure effect (geometric factor)