Silicon nitride drum resonator for phonon-cavity electromechanics
Résumé
Silicon nitride (SiN) mechanical resonators are attractive for sensing and signal processing because of their nanogram effective mass and high-quality factor, with a typical resonance frequency in the MHz range. Up to now, SiN electromechanical resonators are based on double-clamped beam structures, with limited space for making trade-offs among quality factors, resonance frequency, and coupling strength with external circuits.
Here, we will present our recent achievements in developing a novel electromechanical system, consisting of capacitively coupled two distinct resonators: a SiN drum resonator and an aluminum one [1]. The whole device structure can be viewed as a parallel plate capacitor, where each plate is a membrane drum. Integrated with a versatile platform composed of microwave reflectometry and a microwave cavity, both resonators can be manipulated and detected independently. The ultra-clean fabrication process allows to have SiN drum resonators with typical resonator frequencies in ~10 MHz range and high-quality factor (Q) ~104 at the room temperature, reaching the current state of art. In the nonlinear region, its Duffing parameter is about 10 times smaller than the theoretical estimate based on membrane model. While, for the Al drum with resonance frequency ~3 MHz, we could not find the nonlinear region with the same electrostatic driving force and its quality factor is two orders lower than that of SiN drum, at room temperature. With this unique device structure, we investigated phonon-cavity mechanics by taking the SiN drum as a phonon cavity and performing double-tone operations, through analogue to microwave optomechanical system [2]. Here, it is quite different from conventional optomechanical systems in which the mechanical damping rate is usually much smaller than that of the coupled cavity. Electromechanically induced transparency and amplification of input signals have been demonstrated by sideband pumping the phonon-cavity. This unique coupled system gives access to observe the phonon-cavity force affecting mechanical damping rate of both movable objects. The measurement results are in good agreement with our analytical calculations based on electrostatic coupling model. Our results open up new possibilities in the study of phonon-cavity based signal processing in the classical and potentially in the future in the quantum regimes.
[1] X. Zhou, et al., Nano Lett. 21 (13), 5738–5744 (2021)
[2] A Pokharel, et al., arXiv:2204.04641 (2022)