A quantum mixer at 350 GHz based on superconductor-insulator-superconductor (SIS) junctions.

The central issue of this thesis is the application of the superior qualities of superconductor-insulator-superconductor (SIS) mixers at submillimeter wavelengths. After the discovery of photon assisted quasi particle tunneling in SIS junctions, very low noise heterodyne mixers, employing these junctions as mixing element have been developed at millimeter frequencies. At these frequencies the voltage span associated with the photon energy, hf/e, is large enough to cause clearly defined photon assisted tunnelling steps at a good quality SIS DC IV-curve. If that is the case the junction functions as a quantum mixer, for which a quantum limited noise contribution and possible conversion gain are predicted. At 37 GHz and around 100 GHz very low noise temperatures have indeed been realized with SIS mixers, much lower than with Schottky diodes that behave as classical resistive mixers. ...

Zie: Summary and outlook

Summary and outlook

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