Quantifying Dichroic Filter Effects in Angle-Resolved Raman Spectroscopy

The fidelity of polarization-resolved Raman spectroscopy is critically dependent on the optical components within the instrumentation, yet the impact of dichroic edge filers in advanced Raman instrumentation has remained largely unexamined. Here, we present a systematic investigation into the polarization distortions introduced by dichroic edge filters, particularly in measurements involving anisotropic materials such as Si(100)[1]. Through a combination of experimental 2D-polarization mapping and theoretical modeling, we demonstrate how these filters impart phase shifts between s- and p- polarized components of the Raman scatter. By modeling each wavelength-dependent dichroic filter as a waveplate, we recover the true polarization response and quantify the distortions for each color. In contrast, Volume Bragg Grating (VBG) filters demonstrate minimal impact on polarization fidelity, offering a compelling alternative to dichroic filters. Using bulk phase 2H-MoS₂ and Al₂O₃ as testing materials, we establish a reproducible methodology for angle-resolved polarization mapping and highlight the importance of optical component characterization. These findings not only recalibrate our expectations of instrument behavior but also lay the groundwork for more reliable helicity-resolved Raman spectroscopy and future explorations of chiral phonons.