Ptychographic imaging ellipsometry with extreme ultraviolet light

Quantitative optical imaging is an important diagnostic tool for metrology and materials science. Especially in the extreme ultraviolet wavelength range, the combination of high spatial resolution and sensitivity to material properties holds promise for quantitative characterization of complex nanostructures. Unlocking this potential requires an approach that links the relevant material properties to optically measurable observables in a spatially resolved way. Here we show that high-resolution maps of the complex refractive index of a multi-element nanostructure can be reconstructed from polarization-resolved extreme ultraviolet ptychography measurements. We record ptychography data in a reflection geometry for two incident polarization states and variable angle of incidence, and show that the resulting amplitude and phase information can be analysed to yield accurate maps of the local refractive index and surface profile, using an automatic-differentiation-based reconstruction framework. Our approach enables determination of local material composition through a segmentation analysis, as well as high-resolution quantitative imaging of optically addressable properties of nanostructures.