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A SEM image of a part of an HEB chip including the logarithmic-spiral antenna and the mixing element at its apex. The inset is a close-up of the central part of the chip; the length of the mixer is 120 nm.
A typical HEB resistance-temperature curve. The proximity effect at the NbN-Au interface is responsible for the two transitions below the first one at about 9 K. The HEB size is .
Top: current-voltage characteristics of an HEB mixer driven by a 2.5 THz gas discharge laser. The optimal voltage range is . Bottom: the DSB receiver noise temperature vs IF at the optimal operating point for the best (filled circles) and worst (open squares) mixers from the same batch. In both cases the HEB size is . The dashed line is the fit , with .
The gain bandwidth measurement data for two HEB mixers with different lengths of the mixing element: (circles) and (squares). The solid lines are the fits , with and 3.5 GHz.
The gain bandwidth as a function of the length of the mixing element. The solid curve is the length dependence of the 3 dB rolloff derived from Eqs. (1).
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