Accurate Angle‐Resolved Raman Spectroscopy Methodology: Quantifying the Dichroic Edge Filter Effect

ABSTRACT Angle‐Resolved Raman Spectroscopy (ARRS) is an effective method to analyze the symmetry of phonons and other excitations in molecules and solid‐state crystals. Although there are several configurations of ARRS instruments, the measurement system detailed here utilizes two pairs of linear polarizers and superachromatic half‐wave plates. After the orientations of the linear polarizers are set to fixed angles, the two half‐wave plates rotate independently, through motorized control, enabling 2D linear polarization mapping. Described within is a protocol to achieve high quality ARRS measurements leveraging phonons from easily accessible test materials [molybdenum disulfide (MoS 2 ), sapphire (Al 2 O 3 ), and silicon] to validate the system and operation. Quantitative polarized Raman data strongly depends on the quality of the sample surface and the optics: the order of placement, alignment, and any distortion caused by their coatings. This study identifies the impact of commonly used edge filters on the polarization response of materials with an anisotropic response, as emulated by the phonon in Si(100). We detect and model the significant distortion of the phonon polarization response originating from our dichroic edge filters, the results of which are broadly applicable to optics in most Raman instruments. This ARRS setup also enables helicity‐resolved Raman measurements by replacing the first half‐wave plate with a superachromatic quarter‐wave plate; this configuration is also validated using the Raman response of the aforementioned test materials. This paper aims to enhance the quality and reproducibility of polarized Raman measurements through both instrumental considerations and methodological improvements.