Tunable parametric amplification of a graphene nanomechanical resonator in the nonlinear regime

TL;DR

This paper demonstrates electrically tunable parametric amplification in a graphene nanomechanical resonator operating in the nonlinear regime, revealing the influence of higher-order nonlinearities and achieving a maximum gain of 10.2 dB.

Contribution

It introduces a method for electrical tuning of parametric amplification in nonlinear graphene resonators, accounting for higher-order nonlinear effects.

Findings

Parametric gain increases with pumping power and saturates.

Higher-order nonlinearities influence the Duffing and van der Pol behaviors.

Maximum gain of 10.2 dB achieved at 19 V gate voltage.

Abstract

Parametric amplification is widely used in nanoelectro-mechanical systems to enhance the transduced mechanical signals. Although parametric amplification has been studied in different mechanical resonator systems, the nonlinear dynamics involved receives less attention. Taking advantage of the excellent electrical and mechanical properties of graphene, we demonstrate electrical tunable parametric amplification using a doubly clamped graphene nanomechanical resonator. By applying external microwave pumping with twice the resonant frequency, we investigate parametric amplification in the nonlinear regime. We experimentally show that the extracted coefficient of the nonlinear Duffing force {\alpha} and the nonlinear damping coefficient {\eta} vary as a function of external pumping power, indicating the influence of higher-order nonlinearity beyond the Duffing (~x^3) and van der Pol (~x^2 dx/dt) types in our device. Even when the higher-order nonlinearity is involved, parametric amplification still can be achieved in the nonlinear regime. The parametric gain increases and shows a tendency of saturation with increasing external pumping power. Further, the parametric gain can be electrically tuned by the gate voltage with a maximum gain of 10.2 dB achieved at the gate voltage of 19 V. Our results will benefit studies on nonlinear dynamics, especially nonlinear damping in graphene nanomechanical resonators that has been debated in the community over past decade.