Физика Низких Температур: Том 47, Выпуск 11 (Ноябрь 2021), c. 1045-1052 ( к оглавлению , назад )
Raman scattering of plane-wave and twisted light off chiral molecular liquids
Florian Büscher1, Silvia Müllner1, Dirk Wulferding1,2, Yu. G. Pashkevich1,3, V. Gnezdilov1,4, A. A. Peshkov5,6, A. Surzhykov5,6, and Peter Lemmens1,7
1Institute for Condensed Matter Physics, TU Braunschweig, Braunschweig D-38106, Germany
2Center for Correlated Electron Systems, Institute for Basic Science, Seoul 08826, Republic of Korea
3The Dоnetsk Institute for Physics and Engineering named after O. O. Galkin of NAS of Ukraine
Kyiv 03028, Ukraine
4B. Verkin Institute for Low Temperature Physics and Engineering of NAS of Ukraine, Kharkiv 61103, Ukraine
5Institut für Mathematische Physik, TU Braunschweig, Braunschweig D-38106, Germany
6Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany
7Laboratory of Emerging Nanometrology LENA, Braunschweig D-38106, Germany
Received August 9, 2021, published online September 24, 2021
We present an experimental study of the quasi-elastic Raman scattering (QES) of plane-wave and twisted light by liquid crystals. Depending on their temperature, these crystals can exhibit isotropic, nematic and chiral nematic phases. The question is addressed of how the phase of a crystal and the state of incident light can affect the quasi–elastic energy spectra of the scattered radiation, whose shape is usually described by the combination of Lorentzian and Gaussian components. Special attention is paid to the chiral phase, for which the Raman QES spectrum is dominated by a Lorentzian with reduced linewidth, pointing to diminished disorder and configurational entropy. Moreover, this phase is also known for a regime of iridescence (selective backscattering) which arises when the wavelength of incident light becomes comparable with the chiral pitch length. Detailed measurements, performed in this resonant regime and by employing twisted light, carrying various projections of the orbital angular momentum (OAM), have indicated a low-energy scattering surplus depending on OAM. We argue that this observation might indicate a transfer of angular momentum between light and liquid crystal.
Key words: liquid crystals, quasi-elastic Raman scattering, twisted light.