提出了一种基于法布里-珀罗干涉的方法用于原子力显微镜微悬臂偏移量的检测.设计了一个球面反射镜与微悬臂组成的半球面布里-珀罗腔, 并利用高单色性的激光器作为光源, 激光光束在半球面布里-珀罗腔中多次反射并原路返回形成干涉.根据多光束干涉原理确定干涉光强与腔长之间的关系, 利用强度解调的方法计算微悬臂的偏移量并反馈给原子力显微镜系统.最后根据该方案搭建一套微悬臂偏移检测系统, 实验获得30 nm的工作范围内99.9%的线性拟合度, 微悬臂最小位移分辨力为0.26 nm, 实验结果和理论分析一致, 证明了该系统的实用性.

A method based on Fabry-Perot (F-P) interferometer is proposed to detect the displacement of the micro-cantilever of atomic force microscopy. A hemispherical F-P cavity composed of a spherical mirror and a micro-cantilever is designed. A single frequency laser is used as the light source. The laser beam is reflected multiple times in the hemispherical F-P cavity and returned to the original path to form an interference. According to the principle of multi-beam interference, the relationship between the interference intensity and the cavity length has been determined and the deflection of the micro-cantilever has been calculated by using the intensity demodulation method. Finally, a micro-cantilever displacement detection system has been built. The experiment obtained a linear fit of 99.9% in the working range of 30 nm, and the minimum displacement resolution of the micro-cantilever was 0.26 nm. The experimental results are consistent with the theoretical analysis, which proves the practicability of the system.