Metastructures can precisely manipulate light phases and are widely used in imaging, optical communications, and other fields. Therefore, it is critical to comprehensively and accurately evaluate the optical performance of these structures. However, current characterization techniques mostly rely on local or indirect measurements, making it difficult to accurately assess the core-phase distribution. Moreover, existing phase measurement techniques require complex setups or multiple intensity images for reconstruction. This study presents a wavefront optical characterization method and system based on multiwave lateral shearing interferometry for metastructures. The proposed system possessing a sensor specification of phase resolution of 2 nm (RMS), could retrieve phase information from a single measurement, thereby simplifying the characterization process, requiring no reference beam, and effectively resisting external interference. Furthermore, it integrated a detachable polarization modulation module, enabling adaptation to both polarization-sensitive and polarization-insensitive metastructures. Measurement experiments were conducted on three different metastructure samples with varying functions: a metagrating, a toroidal metalens, and a spiral metamaterial. The measurement results demonstrated the detection of the phase modulation of these metastructures with a high repeatability of < 0.04 rad, showing high reliability and stability.
Cheung et al. (Fri,) studied this question.