When Polarizers Meet Spectroscopy: Recent Advances and Prospects in Characterization of New-Generation Functional Thin-Film Materials

Polarizers are essential optical components for spectroscopic measurement, hyperspectral imaging and polarimetric detection over the past two decades. However, the wide variety of polarizers, characterization strategies, and spectroscopic applications has made it difficult to compare their properties directly and to identify their respective merits and limitations clearly. In this review, the development of polarizers and polarization spectroscopy is initially summarized. Then, the structures, working mechanisms, fabrication strategies and characterization methods of three representative types of functional thin-film polarizers: polyvinyl alcohol (PVA)-I2 polarizers, low-symmetry two-dimensional (2D) functional polarizers (Graphene, Black phosphate, transition metal dichalcogenides (TMDCs)), and sub-wavelength wire-grid polarizers (WGPs) will be discussed systematically. The advantages and intrinsic bottlenecks of these three polarizer types will be compared for concrete spectroscopy-relevant scenarios from all sorts of directions. Afterwards, the gap between optimal structural design and performance improvement is addressed through a summarized methodology based on Mueller–Stokes polarimetry and the Poincaré sphere. Furthermore, characterization techniques, mechanistic insights, and potential applications of polarizers and polarization spectroscopy are presented in these findings, which offer a comprehensive strategy for designing novel structures and inspire future research on next-generation functional thin films for optical displays, molecular structural analysis, polarization imaging and polarization photodetectors.