Acoustic Resonance Tuning by High-Order Lorentzian Mixing.

Nanoscale mechanical resonators have attracted a great deal of attention for signal processing, sensors, and quantum applications. Recent progress in ultrahigh-Q acoustic cavities in nanostructures allows strong interactions with various physical systems and advanced functional devices. Those acoustic cavities are highly sensitive to external perturbations, and it is hard to control those resonance properties since those responses are determined by the geometry and material. In this paper, we demonstrate a novel acoustic resonance tuning method by mixing high-order Lorentzian responses in an optomechanical system. Using weakly coupled phononic-crystal acoustic cavities, we achieve coherent mixing of second- and third-order Lorentzian responses, which is capable of the fine-tunability of the bandwidth and peak frequency of the resonance with a tuning range comparable to the acoustic dissipation rate of the device. This novel resonance tuning method can be widely applied to Lorentzian-response systems and optomechanics, especially active compensation for environmental fluctuation and fabrication errors.

Active Information Manipulation via Optically Driven Acoustic-Wave Interference.

Implementing on-chip information processing systems through photonic-phononic interactions has attracted considerable interest owing to its potential for storing, sensing, and signal processing, but the generation and extinction of acoustic waves are determined by the existence of pump power and the phonon lifetime. Here, we demonstrate the acoustic-wave interference and active information manipulation by optically driven acoustic waves in a silicon photonic-phononic controller-emitter-receiver system. The filtered and transmitted information to the receiver has a narrow bandwidth of 6.2 MHz and can be amplified or canceled with a contrast greater than 40 dB by adjusting the relative microwave phase between the emitter and controller. The pulse-train signals can be transmitted, amplified, and canceled with a 3 dB cutoff frequency of 3.1 MHz. The proposed technique provides a potential solution for highly selective on-chip filtering, phase shifters, and information manipulation, offering new functions to optomechanical signal processing and silicon photonics.