Spatially resolved optical characterization of functional materials using coherence scanning interferometry

Herein, some of the work in adapting white light interference microscopy to perform local spectroscopy for measuring the optical properties of microscopic structures is reviewed. Theoretical and experimental results are shown in which Fourier transform processing of the polychromatic fringe signal combined with careful calibration of the optical system is used to make measurements of local reflectance spectra. This approach captures the spectral information within the entire field of view in a single scan, allowing rapid spectral mapping of spatially extended surfaces. Results are shown of local reflectance spectra measured on different materials and buried under transparent layers with a lateral spot size of between 0.5 µm and several micrometer over a field of view up to 650 × 650 µm. The technique is extended to the measurement of local refractive index and thickness of transparent layers as well as to the size determination of small spherical beads buried in transparent and scattering layers with a priori information. The significance of the work is the potential for local materials characterization in complex, hybrid, and functional materials and even disease detection through the study of living cells. (© 2021 Wiley‐VCH GmbH)