Characterizing lateral distribution of complex refractive index based on quantitative amplitude-phase imaging (QAPI)

Abstract

Accurate characterization of the complex refractive index is crucial for designing and optimizing optical devices. Existing methods for characterizing the complex refractive index, such as spectral-based characterization techniques, primarily focus on determining the refractive index of uniform materials, but face challenges in measuring the spatial distribution and achieving high efficiency. To tackle the problem, we propose a novel method based on quantitative amplitude-phase imaging (QAPI) for complex refractive index measurement. By incorporating a physical model, this method enables efficient reconstruction of the lateral distribution of the complex refractive index in a multipixel imaging setup, offering fast acquisition, high resolution, and a large field of view. The feasibility of the proposed method has been validated through both numerical simulations and experiments. Finally, the method is applied to experimentally characterize the complex refractive index distribution of Sb₂S₃ films after laser-induced phase transition, demonstrating its potential for practical material characterization and process monitoring in advanced manufacturing.