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A sub-millimeter(mm)-wave detector module implementing an InP-based zero-biased Schottky-barrier diode (SBD) has been fabricated. The SBD is monolithically integrated with a short-stub resonant matching circuit for increasing the detection sensitivity as well as providing a biasing circuit. The SBD chip is mounted in a compact J-band (WR-3) rectangular-waveguide-input module for practical use. The module exhibits a peak sensitivity at around 350 GHz due to the characteristics of the matching circuit, and a good linearity of the output voltage against the input sub-mm-wave power. A record sensitivity of 1460 V/W is obtained for the InP-based zero-biased SBD at 350 GHz.

A photonic transceiver module integrating a uni-traveling-carrier photodiode, a Schottky barrier diode, and a planar circulator circuit has been developed for sub-terahertz(THz)-wave reflection-geometry imaging. All the components are assembled in a compact rectangular-waveguide-output package for operation in the J-band (220 - 325 GHz), and continuous sub-THz waves are generated by the photomixing. The frequency dependence of the detection sensitivity of the transceiver module exhibits clear resonant behavior at around 270 GHz. The peak internal signal-to-background (S/B) ratio is measured to be as large as about 10. The characteristic of the fabricated transceiver is evaluated by measuring two-dimensional images of a test sample at frequencies from 240 to 310 GHz. Although the image resolution degrades with signal frequency deviation from the resonant condition due to the S/B ratio decrease, it is confirmed that a practical contrast can be obtained for a bandwidth of about 40 GHz even with an S/B ratio below one. Based on these results, the reflection-geometry in-vivo imaging of a human finger at 270 GHz is successfully demonstrated.