Accurate modelling and measurement of the impedance match between UTC photodiodes and THz antennas

Maximising the power extracted from UTC photodiodes is central to the successful realisation of photonic terahertz emitters. For antenna integrated UTCs this requires the optimisation of the impedance match between UTCs and antennas. We present a comprehensive investigation of the UTC output impedance up to 400 GHz, by means of a semi-analytical approach and using 3D full-wave modelling. We introduce a new, accurate, UTC circuit model, exhibiting very good agreement with the measurements. By properly taking into account the UTC-to-antenna impedance match, we demonstrate successful prediction of the absolute level of power radiated by a bow-tie antenna integrated UTC.