Angular Momentum Superposition Beams‐Based Interferometer

Abstract Orbital‐angular‐momentum (OAM) beams‐based interferometer has been found various applications in high‐precision metrology. However, most of its applications reported to date are limited to 1D ones, and the simultaneous measurements for multidimensional displacement have rarely been explored. Here an angular momentum superposition beams‐based interferometer is first proposed and demonstrated, in which the phases‐changes induced by rotational and linear displacements, are independently carried by an angular momentum superposition (SOAMS) beam containing different spin and orbital angular momenta, and thus can be simultaneously detected. In accordance with the proposed interferometry, a new phase‐demodulation method is experimentally demonstrated, which is operated in the domain of the OAM complex spectrum and thus enables accurate yet high efficient extraction of the phase‐change information from the captured OAM interferograms. As typical results, rotational and linear displacements are simultaneously and accurately measured with accuracies of 2.89° and 16.04 nm, respectively. The proposed interferometry and the corresponding phase demodulation method may open a new way to realize the OAM beams‐based multidimensional metrology.