Dual-frequency differential coupling Fabry-Perot interferometric displacement measurement achieves picometer accuracy in air

A differential coupling Fabry-Perot (F-P) interferometric measurement method based on dual frequency-stabilized lasers is proposed, and a corresponding displacement measurement device is constructed. Displacement measurement with picometer-level accuracy is achieved in an air environment. This method subverts the traditional mindset that F-P interferometric displacement measurement requires optical frequency tuning; moreover, it only needs a dual-frequency laser with a frequency stability of the order of 10^-8 (whereas traditional methods require frequency measurement accuracy better than 10^-12) to achieve a displacement measurement resolution of 0.36 pm. Experimental results demonstrate that the measurement repeatability of this device reaches 28 pm in air, with the measurement stability better than ±23 pm. This measurement method has broad application prospects in the fields of metrological science and precision engineering.