State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China.
Sensors (Basel). 2018 Jun 26;18(7):2036. doi: 10.3390/s18072036.
Optical coupling between subwavelength grating pairs allows for the precise measurement of lateral or vertical displacement of grating elements and gives rise to different types of displacement and inertial sensors. In this paper, we demonstrate a design for a nano-optomechanical accelerometer based on a subwavelength grating pair that can be easily fabricated by a single Silicon-on-insulator (SOI) chip. The parameters of the subwavelength grating pair-based optical readout, including period, duty cycle, thickness of grating and metal film, and the distance of the air gap, were optimized by combining a genetic algorithm and rigorous coupled wavelength analysis (RCWA) to obtain the optimal sensitivity to the displacement of suspended grating element and the acceleration. A corresponding mechanical design was also completed to meet the highly sensitive acceleration measurement requirement while considering the mechanical cross-axis sensitivity, dynamic range, bandwidth, and fabrication feasibility. This device was verified by both RCWA and finite-different-time-domain methods, and a tolerance analysis was also completed to confirm that it is able to achieve the extremely high optical displacement sensitivity of 1.8%/nm, acceleration-displacement sensitivity of 1.56 nm/m, and acceleration measurement sensitivity of more than 2.5%/m, which is almost one order of magnitude higher than any reported counterparts. This work enables a single SOI-based high performance accelerometer, and provides a theoretical basis and fabrication guides for the design.
亚波长光栅对之间的光耦合允许对光栅元件的横向或垂直位移进行精确测量，并产生不同类型的位移和惯性传感器。在本文中，我们展示了一种基于亚波长光栅对的纳米光机械加速度计的设计，该设计可以通过单个绝缘体上硅（SOI）芯片轻松制造。通过结合遗传算法和严格耦合波分析（RCWA）对基于亚波长光栅对的光学读出参数（包括周期、占空比、光栅和金属膜的厚度以及气隙的距离）进行了优化，以获得对悬浮光栅元件的位移和加速度的最佳灵敏度。还完成了相应的机械设计，以在考虑机械交叉轴灵敏度、动态范围、带宽和制造可行性的情况下满足高灵敏度的加速度测量要求。该器件通过 RCWA 和有限差分时域方法进行了验证，并完成了容差分析以确认其能够实现 1.8%/nm 的超高光学位移灵敏度、1.56nm/m 的加速度-位移灵敏度和超过 2.5%/m 的加速度测量灵敏度，这几乎比任何报道的同类产品都高一个数量级。这项工作实现了基于单个 SOI 的高性能加速度计，并为设计提供了理论基础和制造指南。
