Suspended tunnel junction bolometers for terahertz range

Implementation of high resolution passive THz cameras operated at cryogenic temperatures of a few Kelvin benefits from a large number of pixels. At present, building a cryogenic multiplexed read-out circuit represents a challenging task. Here we propose and demonstrate broadband niobium-based tunnel junction bolometers operating in equilibrium regime at 4 K, and read out with a room temperature amplifier with feedback. The implemented scheme allows independent impedance matching for the THz antenna and for the readout. Electrical feedback in the readout scheme eliminates the need for magnetic fields to suppress the supercurrent of the junction. We present electrical and preliminary optical measurements of the detectors. We also analyze a possible scheme for time-domain multiplexing.