- Room 1008 Bldg 937
Dr. Sascha Preu - University of Erlangen-Nuremberg, Germany
Frequency tunability is an essential feature for many THz applications, such as spectroscopy or detection of hazardous chemical compounds. We develop continuous-wave photomixers with a tunability from <100 GHz to about 2 THz. The beat signal of two lasers generates a THz AC current within the device that is radiated by an antenna. The photomixer consists of a superlattice of p-i-n diodes. The individual p-i-n diodes are interconnected with ErAs-enhanced recombination diodes. The low resistance of the n-ErAs-p diodes ensures a small device resistance while the superlattice of the p-i-n diodes reduces the device reactance. We will revise the latest developments showing power levels of more than 0.1 mW at low frequencies and still 0.65 W at 1 THz. We will show arrayed photomixers with coherent emission for generation of sharp THz spots at stand-off distances.
In terms of detection, we will show latest results on rectifying field effect transistors. An incident THz field modulates the carrier concentration in the gated region and the carrier velocity simultaneously, resulting in rectification. The rectification effect still works much above frequencies where the transistor has gain. We will show applications of such detectors as direct detectors, homodyne mixers with antenna-coupled devices and as high power detectors with antenna-free large area detectors. We will show potential applications for both sources and detectors such as isotopologue-resolved spectroscopy of water. We will also show polarization resolved sprectroscopy of rare-earth semiconductor compounds. ErSb:GaSb or ErSb:InGaSb samples show segregation of ErSb in regularly arranged nanowires. Due to the conductance of these wires, the samples act like grown wire grid polarizers.