Ultrasensitive Mode-Localized Voltmeter Based on Asymmetric Weakly Coupled Resonators

Mode localization is a phenomenon where small perturbations significantly alter the mode shapes of coupled resonators. This principle enables the development of highly sensitive sensors. Mode-localized sensors typically use two identical resonators as the core structure, but this study pioneers asymmetric weakly coupled resonators (AWCRs) into voltmeters and amplifies electrostatic forces through micromechanical levers, achieving unprecedented levels of sensitivity, effectively pushing the boundaries of sensitivity. The voltmeter consists of AWCRs and two capacitor arrays. The capacitor array converts the voltage into electrostatic force, inducing stiffness perturbation in the resonator. This perturbation disrupts the energy balance of the AWCRs, leading to a variation in their amplitudes. By measuring the amplitude ratio between the two resonators, the voltage magnitude can be determined. The amplitude ratio of the voltmeter changes from 2.52 to 22.84 as the dc voltage ranges from 0 to 10 mV, with a sensitivity of 1987/V. The sensitivity of the voltmeter in this study is about 60 times higher than the mode-localized voltmeter based on symmetric weakly coupled resonators. The noise floor, resolution, and stability of the voltmeter are 95.6 nV/√Hz, 192.4 nV, and 142.4 nV, respectively, competitive compared with that of other high-performance voltmeters.