Intermodulation Gain in Nonlinear NbN Superconducting Microwave Resonators

TL;DR

This paper demonstrates that NbN superconducting microwave resonators can achieve intermodulation gain exceeding unity, with gains up to 15 dB, marking a novel observation in superconducting resonator research.

Contribution

The study reports the first observation of intermodulation gain greater than one in superconducting NbN resonators, highlighting their potential for microwave amplification.

Findings

Intermodulation gain up to 15 dB observed

Gain occurs at the onset of instability in the resonator

First report of intermodulation gain > 1 in superconducting resonators

Abstract

We report the measurement of intermodulation gain in NbN superconducting stripline resonators. In the intermodulation measurements we inject two unequal tones into the oscillator, the pump and signal, both lying within the resonance band. At the onset of instability of the reflected pump we obtain a simultaneous gain of both the idler and the reflected signal. The measured gain in both cases can be as high as 15 dB, whereas to the best of our knowledge intermodulation gain greater than unity in superconducting resonators has not been reported before in the scientific literature.