Ultra-Broadband Microwave Frequency-Comb Generation in Superconducting Resonators

TL;DR

This paper reports the generation of ultra-broadband microwave frequency combs spanning 0.5 to 20 GHz using superconducting niobium-titanium nitride resonators at 3 K, with precise spectral control and theoretical validation.

Contribution

It demonstrates the first ultra-broadband microwave combs in superconducting resonators with detailed theoretical analysis and high spectral accuracy.

Findings

Frequency combs cover at least 6 octaves.

Sideband spacing accurate to 1 part in 10 million.

Spectrum matches perturbation theory predictions.

Abstract

We have generated frequency combs spanning 0.5 to 20 GHz in superconducting half wave resonators at T=3 K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory and the measured spectrum is shown to agree with the theory. The sideband spacing is measured to be accurate to 1 part in 10 million. The sidebands coalesce into a continuous comb structure that has been observed to cover at least 6 octaves in frequency.