Single-spot two-dimensional displacement measurement based on orbital-angular-momentum multiplexing interferometry

Benefiting from the unique helical phase distribution of orbital-angular-momentum (OAM) beams, the OAM beam-based interferometer (OAMI) has been proven to have the potential for high-accuracy measurement. In this study, by employing the orthogonal properties of OAM beams with different topological charges, an OAM multiplexing interferometer was first proposed to realize a single-spot two-dimensional (2D) displacement measurement. Experimental results show 2D displacements ranging from 0 nm to 500 nm with 100 nm step can be simultaneously measured with 12.94 nm maximum standard deviations. Moreover, many types of two-dimensional trajectories can be accurately measured. The proposed OAM multiplexing interferometry may open a new way to multidimensional metrology.