Microwave nonlinear resonance incorporating the helium heating effect in superconducting microstrip resonators

Nonlinear microwave phenomena in superconducting niobium-teflon microstrip resonators cooled by liquid helium are studied. Helium heating caused by the losses of microwave power in superconductor changes the resonant frequency because of the temperature dependence of helium permittivity. Manifestations of this thermal instability discover a new type of nonlinear phenomena including the generation of the monochromatic microwave pulses, generation of acoustic signals. The found nonlinear resonances are explained by thermally induced variations of the helium dielectric permittivity caused by the microwave power dissipated in superconductor, which enable incorporating the jump nonlinearity of a liquid-vapour phase transition in helium