Experimental realization and spectral sensitivity analysis of multiple-order barite wave plates in the near-infrared region of the spectrum

We report the first, to our knowledge, systematic experimental realization and quantitative chromatic-sensitivity analysis of multiple-order wave plates fabricated from natural single-crystal barite in the near-infrared (NIR) spectral region. In the present work, wave plates of varying thicknesses were designed and demonstrated at key NIR wavelengths (985, 1062, 1310, and 1550 nm). The phase retardation was analyzed using a Cauchy dispersion-based model, and the spectral sensitivity was quantified through differentiation of the retardation expression with respect to wavelength. The results reveal that the chromatic sensitivity is dominated by the geometrical phase term and scales linearly with both the wave-plate order m and plate thickness t . Furthermore, the spectral sensitivity increases significantly at shorter wavelengths due to the (1/ λ 2 ) dependence of the dominant term. Experimental Gaussian fits confirm the wavelength-dependent bandwidth narrowing at higher orders. These findings provide a comprehensive understanding of the chromatic behavior of multiple-order barite wave plates and establish design guidelines for near-infrared polarization control applications. The present work represents, to our knowledge, the first quantitative framework linking birefringence dispersion, wave-plate order, and chromatic sensitivity in natural barite crystals for near-infrared polarization applications.