Improved Nb SIS devices for heterodyne mixers between 700?GHz and 1.3?THz with NbTiN transmission lines using a normal metal energy relaxation layer

In this paper, we demonstrate experimentally the implementation of a niobium-trilayer junction with an aluminum-oxide tunnel barrier, embedded in a high-gap superconducting niobium-titanium-nitride circuit. Previously reported heating by quasiparticle trapping is removed by inserting a normal metal layer of gold between the niobium junction and...

Magnetic field dependence of the coupling efficiency of a superconducting transmission line due to the proximity effect

The coupling efficiency of a Nb superconducting transmission line has been measured using a Fourier transform spectrometer for different magnetic fields. It is found that the coupling decreases with increasing magnetic field when the frequency is close to the gap of the Nb superconductor. This is attributed to the changes of the surface...

Niobium titanium nitride-based superconductor-insulator-superconductor mixers for low-noise terahertz receivers

Integrating NbTiN-based microstrip tuning circuits with traditional Nb superconductor-insulator-superconductor (SIS) junctions enables the low-noise operation regime of SIS mixers to be extended from below 0.7?to?1.15?THz. In particular, mixers incorporating a NbTiN/SiO2/NbTiN microstrip tuning circuit offer low-noise performance below 0.8–0.85...