A Methodology to Measure Input Power and Effective Area for Characterization of Direct THz Detectors

This paper presents a test setup and measurement methodology for the characterization of direct terahertz (THz) detectors. The detector under test is illuminated by a continuous wave THz source and its voltage response is measured using a lock-in amplifier. A reference detector is used to measure the input power density of the receiver antenna. The calculation of the effective area is done by measuring E and H plane radiation patterns of the receiver antenna. Several measurement techniques are shown in order to achieve a reliable characterization of the detector with different advantages and disadvantages. In addition, a setup modification is done for the removal of the electronically induced background noise due to the coupling of the signals through cables. Based on the measured input power, the performance parameters of an antenna-coupled field-effect transistor (FET)-based THz detector are measured and presented. This measurement methodology can also be used to characterize other direct THz detectors.