Influence of the ESR saturation on the power sensitivity of cryogenic sapphire resonators

TL;DR

This paper investigates how ESR saturation affects the power sensitivity of cryogenic sapphire resonators, revealing non-linear behaviors that can optimize their performance in ultra-stable oscillators.

Contribution

It provides the first clear observation of non-linear power sensitivity due to ESR saturation in cryogenic sapphire resonators, enhancing understanding and optimization of their operation.

Findings

Non-linear power sensitivity observed in cryogenic sapphire resonators.

ESR saturation explains the non-linearity in the resonator behavior.

Optimization strategies for cryogenic sapphire oscillators are proposed.

Abstract

Here, we study the paramagnetic ions behavior in presence of a strong microwave electromagnetic field sustained inside a cryogenic sapphire whispering gallery mode resonator. The high frequency measurement resolution that can be now achieved by comparing two CSOs permit for the first time to observe clearly the non-linearity of the resonator power sensitivity. These observations that in turn allow us to optimize the CSO operation, are well explained by the Electron Spin Resonance (ESR) saturation of the paramagnetic impurities contained in the sapphire crystal.