Discrimination of Chiral and Helical Contributions to Raman Scattering of Liquid Crystals using Vortex Beams

Abstract

We use vortex photon fields with orbital and spin angular momentum to probe chiral fluctuations within liquid crystals. In the regime of iridescence with a well-defined pitch length of chirality, we find low energy Raman scattering that can be decomposed into helical and chiral components depending on the scattering vector and the topological charge of the incident photon field. Based on the observation of an anomalous dispersion we attribute quasi-elastic scattering to a transfer of angular momenta to roton-like quasiparticles. The latter are due to a competition of short-range repulsive and long-range dipolar interactions. Our approach using a transfer of orbital angular momentum opens up an avenue for the advanced characterization of chiral and optically active devices and materials.

5 pages, 3 figures, Physical Rev. Lett., in print (2022)

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• Electromagnetic Force and Momentum
• Angular Momenta and Spin-Orbit Interaction of Nonparaxial Light in Free Space
• Roton-type mode softening in a quantum gas with cavity-mediated long-range interactions
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Cited by in corpus (4)

• Customized optical chirality of vortex structured light through state and degree of polarization control
• Nonlinear vortex dichroism in chiral molecules
• Topological-charge-dependent dichroism and birefringence of optical vortices
• Emergent spin and orbital angular momentum of light in twisted photonic bilayer