Birefringence in the Polarized Raman Scattering of Biaxial van der Waals α-MoO_3

摘要

The effect of birefringence in anisotropic materials has been a long-termissue for polarized Raman scattering. In this work, the polarization-dependentRaman scattering in anisotropically birefringent materials is modeled withbirefringence considered in the fundamental polarization selection rule. Thebirefringence-induced polarization transformation is treated as a tensor in thecalculation of Raman scattering intensity. The validity of this theory is furtherdemonstrated in experiments by taking angle-resolved polarized Ramanmeasurements on the basal and cross planes of α-MoO_3—a typical biaxialvan der Waals crystal with strong in-plane and out-of-plane anisotropy. Theanomalous angular dependency of polarized Raman scattering intensity canbe well reproduced by the modified theoretical model with fitted real-valuedRaman tensors and birefringence-related parameters. It can be concludedthat this work can provide a valuable reference and guidance for quantitativeanalyses of anisotropic materials by using polarization-resolved Raman scatteringspectroscopy.