Operation of quasi-optical a THz detectors in heterodyne regime

Abstract

In recent years Schottky-diode technologies gain influence in THz systems because of their large sensitivity, wide range, high power capability and room-temperature operation. Schottky diodes rectify the RF signal directly and therefore change their current-voltage characteristic. Considering the square-law detection for low-power and linear detection for high power, dynamic ranges of typically 90dB can be achieved. Direct detectors with quasi-optical interface have been developed, as an alternative to nearly frequency-independent Golay-Cell THz detectors with a great advantage of very short response time. Such detectors may be extremely sensitive or provide a ultra-wide operation range from about 50GHz up to beyond 2THz in a single device, which facilitate emerging of new application areas for THz technology. Nevertheless, main drawback of direct detectors for many applications is the luck of frequency and phase information of detected signal. A commonly-used approach to get this information is the comparison of the incident RF-signal with a reference one. For this reason homodyne or heterodyne regime is commonly used. Operation of quasi-optical detectors in homodyne regime has already been demonstrated.