Length measurement method with resolution of picometer using high-finesse optical cavity and regular crystalline lattice

本研究项目的一个目的是为了促进纳米技术的发展，开发一种直接可追溯到计量器定义的皮度计分辨率的长度测量方法。利用谐振激光器和稳频激光器之间的拍频，可以随着腔的谐振频率的变化来测量光学腔的变化。并且空穴的变化也可以用规则的晶格来校准。取得了以下研究成果：(1)研制了光腔样机和测量系统。光腔的一端镜由高刚性挠性工作台支撑，其驱动工具为大功率PZT驱动器。光腔采用精确度分别为400和1000的两个反射镜。利用锁定检测方法检测谐振信号。锁定检测电路由微波混频器和微波低通滤波器组成。并研制了检测和记录拍频的电路和软件。(2)利用上述实验系统进行了共振反馈实验。利用上述系统，可将可调谐激光二极管的频率调谐到光腔的谐振频率。当改变一端光学腔的位置时，可以根据谐振频率的偏移来确定反射镜的位移。并与激光干涉仪进行了比较。测量结果可以达到0.1 nm以下的测量分辨率。(3)指定了精确度在5000以上的光腔。在光学腔的情况下，使用上述系统进行位移测量时，分辨率有望达到30 pm。

A purpose of the research project is to develop a length measurement method with resolution of picometer, which is directly traceable to the meter definition, in order to promote the Nanotechnology. A change of an optical cavity can be measured with the change of the resonance frequency of the cavity using the beat frequency between the resonance laser and the frequency stabilized laser. And the change of the cavity can be also calibrated with a regular crystalline lattice. The following results are obtained.(1)Prototype of the optical cavity and the measurement system were developed. The one end mirror of the optical cavity is supported by the high rigid flexure stage, whose driving tool is a high power PZT actuator. Two mirrors, whose finesse are 400 and 1000, respectively, are used for the optical cavity. Resonance signals are detected with a lock-in detection method. The lock-in detection circuit consists of a microwave mixer and a microwave low-pass filter. A circuit and a saftware to detect and record the beat frequency were also developed.(2)Resonance feedback experiment was performed using the above experimental system. A frequency of the tunable laser diode can be tuned to the resonance frequency of the optical cavity using the above system. When the position of the one end optical cavity is changed, the displacement of the mirror can be determined from the shift of the resonance frequency. The results were compared with the laser interferometer. The measurement resolution of 0.1 nm or less can be achieved from the results.(3)The optical cavity whose finesse of 5000 or more was designated. With the optical cavity, we expect the resolution of 30 pm for the displacement measurement using the above system.