Dual-path OAM-Gaussian interference for simultaneous dynamic two-dimensional micro-displacement sensing

High-precision two-dimensional displacement sensing is important for micro-/nano-manufacturing, precision positioning, and motion-tracking systems. However, simultaneously achieving real-time operation, high accuracy, strong alignment robustness, and an extended measurement range within a simple optical architecture remains challenging. Here, we report a dynamic two-dimensional micro-displacement sensing method based on dual-path orbital angular momentum (OAM)-Gaussian coaxial interference. By transforming a single OAM beam into two coaxial sensing channels, the system enables simultaneous readout of X- and Y-axis displacements through independent petal-pattern rotations within one interferometric platform. Combined with spiral intensity sampling and fast Fourier angular spectrum analysis, the method supports real-time angle retrieval with reduced computational complexity. Theoretical and experimental results further show that the OAM-Gaussian configuration exhibits improved robustness against misalignment compared with conventional OAM-OAM schemes. Experiments demonstrate nanometer-level accuracy, sub-meter-scale measurement range, and real-time reconstruction of complex two-dimensional trajectories. Relying only on standard optical components and ordinary reflective targets, the proposed method provides a practical approach for high-performance optical metrology and dynamic motion sensing.