Dual-parameter interferometric measurement using orbital angular momentum beams.

Orbital angular momentum (OAM) beam interferometer can be employed to measure micro-phase variations in optical path, thereby enabling the sensing of physical parameter changes. However, most existing OAM-based interferometric systems are limited to single-parameter measurements. In this work, we propose a dual-parameter measurement system based on an OAM beam interferometer. This system analyzes the interferogram of the received beam and utilizes the power and the rotation angle to calculate the phase variations of the two independent optical paths. We theoretically derive the relationships between the interferogram power, rotation angle, and the phase variations of the two paths, and apply these relationships to phase demodulation. The theoretical measurement resolutions of the two branches can reach 0.10° and 2 nm, respectively. An experimental setup is further implemented to validate the proposed method. The results show that the system achieves an accuracy exceeding 99% in single-parameter measurements. For simultaneous dual-parameter measurements, the root mean square error (RMSE) of the Euclidean distance is 3.10°. The experimental measurement resolutions of the two branches can reach 0.40° and 2 nm, respectively. Both theoretical analysis and experimental results demonstrate that the proposed system provides a practical and effective approach for dual-parameter sensing, offering valuable guidance for the design of OAM-based interferometric measurement systems.