Cryogenic excitation and detection of terahertz radiation in microstrip circuits

There are widespread potential applications for guided-wave terahertz (THz) frequency measurements in the study of condensed matter physical systems, many of which require a low temperature environment. Here we report on the excitation, propagation and detection of ~picosecond duration (>1 THz bandwidth) electrical pulses at cryogenic temperatures (~4 K) in microstrip circuits. A reduction in both the excitation and propagating pulse widths is observed compared to room temperature data. These results indicate that, in cryogenic THz circuits, the electrical properties of low-temperature-grown GaAs are highly suited to photoconductive excitation and detection, and that benzocyclobutene (BCB) acts an effective THz dielectric material.