International System of Units (SI) Traceable Noise-Equivalent Power and Responsivity Characterization of Continuous Wave ErAs:InGaAs Photoconductive Terahertz Detectors

A theoretical model for the responsivity and noise-equivalent power (NEP) of photoconductive antennas (PCAs) as coherent, homodyne THz detectors is presented. The model is validated by comparison to experimental values obtained for two ErAs:InGaAs PCAs. The responsivity and NEP were obtained from the measured rectified current, the current noise floor in the PCAs, and the incoming THz power for the same conditions. Since the THz power measurements are performed with a pyroelectric detector calibrated by the National Metrology Institute of Germany (PTB), the experimentally obtained values are directly traceable to the International System of Units (SI) for the described conditions. The agreement between the presented model and the experimental results is excellent using only one fitting parameter. A very low NEP of 1.8 fW/Hz at 188.8 GHz is obtained at room temperature.