Angular dependencies of the Raman scattering intensity of on polaritons in a gallium phosphide crystal

Raman scattering of light by phonons and polaritons in a sample of gallium phosphide was measured. For the excitation, a non-focused beam of a 532 nm single-mode laser was used. The collection of scattered radiation was carried out using a moving mirror of small diameter, which made it possible to measure the spectra of scattered light in the scattering angle range of 0.60–80 with an angular total divergence of 0.4$^\circ$. For different crystallographic directions, the intensities of the polarized components of the Raman scattered light were measured on longitudinal, transverse phonons and polaritons in the region of strong dispersion of the polariton branch for three fixed axial scattering angles. The components of scattering on longitudinal optical phonons and polaritons have a strong dependence on the crystallographic direction, as theory predicts, and the component of scattering on transverse optical phonons does not depend on the crystallographic direction. It was found that the intensity of scattering on transverse optical phonons correlates with the width of the spectral line of scattering on a polariton. A mechanism is proposed to explain this correlation.