Wide-range anti-disturbance orbital angular momentum interferometer

Due to its potential for pm-level displacement measurement accuracy, orbital angular momentum (OAM) interferometer recently has attracted extensive research interest. However, the displacement range of common OAM interferometer always is limited to submicrometer level due to the phase ambiguity in demodulation. To overcome this limitation, we firstly proposed a polarization-separated dual-wavelength OAM interferometer. The measurement range can be increased by three orders of magnitude through dual-wavelength interferometry. Benefiting from the unique optical structure design of polarization-separated common optical path, dual-wavelength interferograms can be synchronously and stably acquired using a polarization camera. Moreover, the impact of environmental disturbances can be further suppressed by using OAM beams with opposite topological charge. Experimental results show that a 7500.0 nm displacement is measured as 7447.1 nm (0.7% error), while step measurements achieve linearity >0.999. The proposed interferometer can realize a single-frame wide-range displacement measurement, maintaining good stability and measurement accuracy, which may provide a promising technical solution for wide-range high-precision measurement.