Nonlinear microwave metamaterial resonators using gravitational restoring force realized on a microfabricated perforated substrate

Abstract

We demonstrate microwave metamaterial with enhanced nonlinearity enabled by a significant mass and loss reduction due to perforated SU-8 substrate supporting self-rotating split ring resonators utilizing gravity as a restoring force. Forces involved in resonator movement are analyzed, and mechanical features of the structure are optimized. Unconventional microfabrication technique allowing creation of metal coated SU-8 structures with non-coincident metal and substrate patterns is introduced, resulting in a robust micrometer sized mesh. The beneficial effects of perforated substrate are demonstrated on electromagnetic properties of single resonators as well as coupled nonlinear resonator pair. Improvement in quality factor of single resonator as a result of reduced substrate mesh density is shown in the microwave frequency range. Nonlinear resonant frequency shift by 0.067 GHz is achieved for a pair of coupled resonators upon increasing the microwave power from 1 mW to 1 W.