Polarimetry analysis and optical contrast of Sb₂S₃ phase change material

Phase-change materials (PCMs) are the cornerstone for the development of reconfigurable and programmable photonic devices. Sb₂S₃ has been recently proposed as an interesting PCM due to its low-losses in the visible and near-IR. Here, we report the use of imaging polarimetry and spectroscopic ellipsometry to reveal and directly measure the optical properties of Sb₂S₃ both in crystalline and amorphous states obtained upon crystallization by annealing in the air of chemical bath deposited amorphous Sb₂S₃. The Mueller Matrix polarimetric analysis reveals the strong anisotropy of the Sb₂S₃ crystallites which crystallize in radial spherulitic domains in contrast to the optical isotropy of the amorphous films. A refractive index contrast of ∆n = 0.5 is demonstrated while maintaining low-losses at telecommunications C-band, i.e., λ = 1550 nm.