An all-cryogenic THz transmission spectrometer

This article describes a THz transmission spectrometer for the spectral range of 2–65 cm ~100 GHz to 2 THz! with a spectral resolution of at least 1.8 cm ~50 GHz! where the source, sample, and detector are all fully contained in a cryogenic environment. Cyclotron emission from a two-dimensional electron gas ~2DEG! heated with an electrical current serves as a magnetic-field tunable source. The spectrometer is demonstrated at 4.2 K by measuring the resonant cyclotron absorption of a second 2DEG. Unique aspects of the spectrometer are that ~1! an ultrabroadband detector is used, and ~2! the emitter is run quasicontinuously with a chopping frequency of only 1 Hz. Since optical coupling to room temperature components is not necessary, this technique is compatible with ultralow temperature ~sub-100 mK! operation. © 2002 American Institute of Physics. @DOI: 10.1063/1.1426231#