Sensitivity measurement and analysis of an ErAs:GaAs coherent photomixing transceiver -: art. no. 134105

A frequency domain transceiver is implemented with a pair of 780-nm-based ErAs:GaAs photomixers, one serving as the transmitter and the other as the receiver. The transceiver is all solid state, operated at room temperature, and has a fast response. The receiver detects the amplitude of the incoming electric field coherently and the sensitivity is limited by 1/f mechanisms which are excited by a photovoltage that is always present in the receiver photomixer. This letter reports the first measurements and calculations of the signal-to-noise (S/N) ratio in the transceiver. Measurement yields a differential terahertz power-to-current sensitivity of 4 mA/W and noise equivalent power of 0.1 pW/Hz. The maximum S/N ratio was 58 dB/rtHz around 86 GHz which is 17 dB lower than our theoretical estimate. The discrepancy is attributed to radiative coupling losses and nonoptimal laser spatial overlap. (C) 2005 American Institute of Physics.