Polarization imaging for gemstone identification and metrology

This study applies polarization raytracing and full-Stokes polarization imaging using transmission, reflection, and side-view configurations to analyze the polarimetric signatures of four brilliant round-cut gemstones: cubic zirconia (CZ), natural diamond, chemical vapor deposition (CVD) synthetic diamond, and moissanite. Raytracing simulations provide a theoretical baseline for ideal light-facet interactions, while experimental measurements of the DoLP, AoLP, and DoCP reveal distinct optical behaviors. Isotropic CZ exhibits symmetric, geometry-driven polarization patterns, while birefringent moissanite shows extreme linear polarization responses dictated by its optical axis. Differences in polarization signatures are observed between the natural and CVD diamond samples examined, despite their identical chemical compositions. The natural diamonds in this study exhibit more symmetric polarization patterns and a distinct secondary DoLP peak (0.46) in transmission, while the CVD samples show more spatially fragmented AoLP distributions and asymmetric DoCP distributions, consistent with stress-induced anomalous birefringence associated with synthetic growth. These trends highlight measurable polarization features that correlate with growth origin in the samples examined. Symmetry features of each gemstone are further evident in the extracted histograms of the polarization parameters. Overall, our results demonstrate the potential of full-Stokes polarization imaging as a non-destructive tool for probing optical structure in gemstones, with possible applications in identification and quality assessment. The observed distinctions between natural and CVD diamonds motivate future investigation to establish the broader applicability of polarization-based characterization.