Complex amplitude measurement with off-axis and phase-shifting methods for characterizing and evaluating metasurfaces

An interferometer with off-axis and phase-shifting methods is developed to quantitatively measure complex amplitude distributions of fabricated metasurfaces. The developed interferometer switches between the off-axis and phase-shifting methods depending on the maximum spatial frequency components of a specimen metasurface. The off-axis method allows complex amplitude measurements from a single interference pattern and is robust to environmental vibrations, whereas the phase-shifting method can achieve high spatial resolutions via sequential recording of multiple interference patterns. We measured the complex amplitude distribution of fabricated metasurfaces using the developed interferometer. This interferometer would be useful for reducing design and fabrication errors and optimizing metasurface structures.