Optomechanical separation of transverse spin and orbital energy flows in liquid crystals

Mur, Urban (author), Čančula, Miha (author), Kobayashi, Hirokazu (author), Ravnik, Miha (author), Žumer, Slobodan (author), Brasselet, Etienne (author)

We report a nondissipative optomechanical approach to separate the spin and orbital components of transverse energy flows of light beams. Focusing on uniformly polarized paraxial fields, the method relies on detecting the radiation-pressure-induced reorientation of the optical axis in anisotropic media—specifically, liquid crystals. Within a perturbative analytical approach, we demonstrate the selective encoding of the transverse spin and orbital components of the Poynting vector into orthogonal orientational elastic modes, whose relative weights are mediated by the Gouy phase. The spatial distributions of spin and orbital momentum can therefore be retrieved without resorting to point-by-point measurements using absorbing or scattering probe particles. Analytical results are supported by a fully self-consistent numerical solution coupling Maxwell’s equations and Landau-de Gennes nematodynamics in three dimensions. This exact framework captures higher-order and nonparaxial effects beyond the analytical perturbative regime and allows us to validate the predicted Gouy-phase-mediated optomechanical response. These results establish a practical route toward optomechanical imaging of the internal momentum structure of light, fostering momentum-resolved optical metrology and light-matter interaction studies with structured beams.

• Language: English
• Keywords: liquid crystals, optomechanics, polarization of light
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: Str. 013235-1-013235-8
• Numbering: Vol. 8, iss. 1
• PID: 20.500.12556/RUL-180308
• UDC: 538.9:535
• ISSN on article: 2643-1564
• DOI: 10.1103/59st-f1mb
• COBISS.SI-ID: 270647043
• Publication date in RUL: 05.03.2026

Record is a part of a journal

• Title: Physical review research
• Publisher: American Phyisical Society
• ISSN: 2643-1564
• COBISS.SI-ID: 32822823

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: tekoči kristali, optomehanika, polarizacija svetlobe