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We compare Terahertz detection by large-area to antenna coupled lumped element field-effect transistors (FETs). The large radiation resistance of Ra=72 Ω of the antenna coupled device improves the responsivity by a factor of 150 as compared to the antenna-less large area device. The LA-FET is an order of magnitude more sensitive than expected from theory.
THz radiation can couple in various undesired ways to THz detectors, e.g. through wires or contact pads, aggravating calculation of sensible values for the device responsivity. We therefore investigate coupling of THz radiation to antenna-less large area field-effect transistors with dimensions in the range of the THz spot size proving that only a very small fraction of power is coupled through the...
We report on 1550 nm driven ErAs:In(Al)GaAs photoconductors implemented as both source and detector in a THz time domain system. The system reaches a peak dynamic range of 80 dB with a source and receiver laser power of 20 mW each. We report in particular on the saturation properties of the emitter. Even with incident optical powers of up to 80 mW, we hardly see any saturation. We demonstrate the...
In this paper, a simple method for the facial expression detection to identify the normal and unusual of expression variations of the human face is proposed. The approach uses the binary edge image to present the shape of facial expression. The modified Hausdorff distance measure is adapted to our approach to compare between the unusual and normal face expression. In our algorithm, it just needs to...
We report on a 4 element linear array of free standing, tunable THz n-i-pn-i-p superlattice photomixers. The individual THz beams are coherently combined at a target plane distance of 4.2 m. The measurements of the interference pattern confirm the theoretically expected quadratic intensity increase of the center beam with the number of sources. At the same time, the beam waist is reduced in one dimension...
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