Ultra-precise distance measurement for nanometrology

摘要

We present experimental results achieved by a method of direct conversion of the relative changes of the measurement optical path of Michelson interferometer to relative changes of the resonant optical-frequency of Fabry-Perot (F.-P.) resonator. We developed the method as a testing process for verification of scale-linearity of Michelson interferometer with total resolution 0,3 nm. The method consists of a mechanical coupled shift of the corner cube mirror of the interferometer measurement arm with one of the mirrors of F.-P. resonator. A piezoelectric transducer (PZT) with approximately 10 microns elongation drives that mechanical shift. An external tunable laser source at 633 nm wavelength provides identification of one of the resonant optical frequency of F.-P. resonator by the frequency locking mechanism with synchronous detection technique in the servo loop feedback. Because definition of the meter unit is based on iodine stabilized He-Ne laser, then the optical frequency of the locked tunable laser is frequency compared with He-Ne-I_2 laser by the heterodyne optical mixing. A fast high-resolution counter counts the resultant radio-frequency signal as a product of the optical mixing. Measured frequency values and values of interference phase acquired by the interferometer are simultaneously sampled step by step for each elongation position of PZT element. The experimental data achieved by F.-P. resonator shows uncertainty of the relative distance change better than 0,01 nm. We verified the scale-linearity of Michelson interferometer to +- 1,0 nm limit.