A terahertz time-domain spectroscopy-based network analyzer

We present a terahertz time-domain spectroscopy-based setup based on photoconductive antennas and a femtosecond fiber laser for measuring the transmission S parameters of electronic devices. To this end, radiation is focused into horn antennas attached to the waveguide-coupled devices under test and coupled out of the device using a similar setup. The terahertz emitter is fiber-coupled in order to allow for flexible selection the measurement geometry. As test cases, the S-21 parameters of several H band (220-330 GHz) amplifiers are measured and show promising results. Also, the response of a W band amplifier is measured, marking the lower frequency boundary for this setup. In both cases, the measurements are compared to measurements retrieved using a commercially available vector network analyzer with frequency extenders, showing rather good agreement. Transmission measurements of "thru" waveguides used as a reference imply our system's ability to measure up to at least 2.5 THz, widely exceeding the bandwidth of currently available network analyzers.