Spectroscopic polarimetric imaging of cholesteric liquid crystals and the influence of large diattenuation to the polar decomposition of Mueller matrix

This paper presents a comprehensive study on spectroscopic Mueller matrix polarimetric imaging of cholesteric liquid crystals (CLCs) and the impact of large diattenuation on the polar decomposition of Mueller matrices. The wavelength of the probing light is designed to cover the regions outside, at the edges of, and inside the photonic bandgap of CLCs, enabling systematic analysis of polarization properties under varying diattenuation levels. By applying the polar decomposition method to measured Mueller matrices, we find that the depolarization power extracted from the decomposition is significantly affected by the magnitude of diattenuation. When diattenuation is large, the extracted depolarization power deviates substantially from the theoretical behavior of an ideal CLC. Finite-difference time-domain (FDTD) simulations and theoretical analysis reveal that measurement errors in the Mueller matrix are amplified when the diattenuation is large, which leads to abnormal results in polar decomposition. Our results indicate that the polar decomposition method should be applied with caution when the diattenuation is large.