Xia Ji, Qiao Qifeng, Sun Haoyang, Huang Yongjun, Chau Fook Siong, Zhou Guangya
Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore.
University of Electronic Science and Technology of China, No. 2006, Xiyuan Ave, Chengdu, 611731, China.
Nanophotonics. 2022 Mar 21;11(8):1629-1642. doi: 10.1515/nanoph-2021-0820. eCollection 2022 Mar.
High-precision detection of electric charge is critical for physical, chemical, and biological measurements. Nanophotonic optomechanical system confines the optical field at the nanoscale and enables a strong interaction between optical cavity and mechanical resonator. Its high optical quality factor cavity and strong optomechanical coupling are promising for precision sensing applications. Here an integrated optomechanical electrometer is proposed for the electric charge sensing using a zipper cavity with a suspended photonic crystal nanobeam (PCN) acting as a movable mechanical resonator. As the electrostatic force arising from the electric voltage to be measured interacts with the mechanical motion of the movable PCN and modulates its resonance through electrostatic stiffening effect, optomechanical coupling transduces the mechanical motion to the optical field with enhanced sensitivity. The resonance shift of the mechanical resonator can be monitored to detect the electric voltage with a sensitivity of 0.007 . Moreover, the sensing performance can be further enhanced with the operation of the optomechanical electrometer in the self-sustained oscillation above threshold power. Owing to the narrow-linewidth of detector radio frequency (RF) spectrum with a large peak-to-noise floor ratio (up to 73.5 dB), the enhanced electrical sensitivity of 0.014 is achieved with a high resolution of . A theoretical minimal detectable electrostatic charge is calculated as by converting the measured electric voltage versus RF shift to an approximatively linear relationship. This on-chip optomechanical electrometry scheme provides a powerful solution to the ultrasensitive determination of charged nanoparticles in biological and chemical applications.
电荷的高精度检测对于物理、化学和生物测量至关重要。纳米光子光机械系统将光场限制在纳米尺度，并使光学腔与机械谐振器之间产生强相互作用。其高光学品质因数腔和强光机械耦合在精密传感应用中具有广阔前景。本文提出一种集成光机械静电计，用于电荷传感，该静电计采用拉链腔，其中悬浮的光子晶体纳米梁（PCN）作为可移动的机械谐振器。由于待测电压产生的静电力与可移动PCN的机械运动相互作用，并通过静电硬化效应调制其共振，光机械耦合以增强的灵敏度将机械运动转换为光场。可以监测机械谐振器的共振频率偏移来检测电压，灵敏度为0.007 。此外，通过在高于阈值功率的自持振荡中操作光机械静电计，传感性能可以进一步提高。由于探测器射频（RF）频谱的窄线宽和大的峰噪比（高达73.5 dB），实现了0.014 的增强电灵敏度和高分辨率 。通过将测量的电压与RF偏移转换为近似线性关系，计算出理论最小可检测静电荷为 。这种片上光机械静电计方案为生物和化学应用中带电纳米颗粒的超灵敏测定提供了有力的解决方案。
