Acousto-Optic Modulation in Silicon Waveguides Based on Piezoelectric Aluminum Scandium Nitride Film

摘要

Aluminum scandium nitride (AlScN) has attracted extensive attention for its excellent piezoelectric properties in the micro-electromechanical system applications. In this work, AlScN is demonstrated to be a promising candidate for on-chip acousto-optic coupling interactions with outstanding piezoelectric properties as well. Based on piezoelectric Al0.6Sc0.4N film deposited on silicon-on-insulator platform, the proposed devices exhibit impressive acousto-optic coupling performances over a short interaction length of 210 mu m with surface acoustic waves actuated by interdigital transducers. Meanwhile, the acousto-optic coupling performances are further improved in a compact spiral waveguide with eight interaction segments, where the measured modulation efficiency is enhanced from -21.5 to -12.5 dB and the radiofrequency (RF) 3-dB bandwidth is narrowed from 4 to 3.1 MHz at central frequency of 3.044 GHz with RF drive power of 18.6 dBm. The measured modulation efficiency is proportional to the incident RF drive power, depicting a linear increasing trend with a slope of one as the RF power increases up to 24.6 dBm. Such acousto-optic devices are capable of achieving broadband acousto-optic modulation and narrow-band microwave photonic filtering. Besides, the designed device structure provides a prospect in single-sideband modulation, acousto-optic frequency shift, and nonreciprocal light propagation.