Terahertz spectroscopy system of gas mixtures based on a solid state superconducting source and a terahertz receiver

In this paper, we demonstrate the application of a terahertz (THz) Josephson oscillator based on a tunnel superconductor-insulator-superconductor (SIS) long junction coupled to a transmitting antenna and emitting a signal to open space, for gas spectroscopy. The oscillator is utilized as an active source, the signal of which is absorbed by a gas mixture in a cell 60 cm long and then detected by a spectrometer based on a SIS receiver with a spectral resolution of better than 100 kHz. In the experiment, the absorption lines of ammonia and water in the THz range were recorded, and the dependence of the absorption spectral characteristics on the pressure of the gas mixture was shown in a wide range (from 0.005 to 10 mbar).