This study presents new antenna schemes suitable for cognitive radio communications. The antenna structures consist of a ultra wide band (UWB) sensing antenna, and a frequency reconfigurable communicating antenna both incorporated into the same substrate. Two different techniques to achieve the required frequency agility are proposed. The first one is based on a rotational motion of the radiating patch whereas the second is based on optical switching. The importance of these techniques is that no bias lines are needed as is seen in the case of RF MEMs, PIN diodes and lumped elements. Prototype antennas were fabricated and a good agreement was observed between the simulated and the measured data.

Avalanche photodiodes (APDs) are essential components in quantum key distribution systems and active imaging systems requiring both ultrafast response time to measure photon time of flight and high gain to detect low photon flux. The internal gain of an APD can improve system signal-to-noise ratio (SNR). Excess noise is typically kept low through the selection of material with intrinsically low excess noise, using separate-absorption-multiplication (SAM) heterostructures, or taking advantage of the dead-space effect using thin multiplication regions. In this work we demonstrate the first measurement of excess noise and gain-bandwidth product in III–V nanopillars exhibiting substantially lower excess noise factors compared to bulk and gain-bandwidth products greater than 200 GHz. The nanopillar optical antenna avalanche detector (NOAAD) architecture is utilized for spatially separating the absorption region from the avalanche region via the NOA resulting in single carrier injection without the use of a traditional SAM heterostructure.

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