Mechano-mechanical parametric coupling in MEMS between GHz and kHz frequency regimes at room temperature

Microelectromechanical systems (MEMS) sensors have been widely used in various fields, but their performance is often limited by thermal fluctuations and detection noise. Inspired by advances in cavity optomechanics, which utilize parametric coupling for precision sensing and noise reduction, we explore a new approach to overcoming these limitations. We demonstrate a purely mechanical parametric coupling system that replaces the optical mode with a GHz surface acoustic wave (SAW) cavity. This system couples the GHz SAW cavity with a kHz micro-cantilever oscillator under ambient conditions, bridging vastly different frequency regimes within a unified framework. This mechano-mechanical coupling is experimentally demonstrated by the generation of red and blue sidebands in the frequency spectrum as direct evidence of energy exchange between the SAW cavity and multiple vibrational modes of the cantilever. Using the standard cavity optomechanics framework, we calculate the coupling strength g₀, which is on the order of 10^-3 Hz, and compare it with previously reported values in optomechanical and electromechanical systems. Our findings establish mechano-mechanical parametric coupling as a practical alternative to conventional optomechanical interactions, offering a new framework for integrating GHz and kHz mechanical resonators into silicon MEMS-compatible platforms.