Interaction of liquid crystals with electromagnetic fields: Mauguin theorem, angular momentum conservation, and optical Freedericksz transitions in twisted nematic liquid crystals

Journal Article · Sat Oct 15 00:00:00 EDT 1988 · Phys. Rev. A; (United States)

DOI:https://doi.org/10.1103/PhysRevA.38.4323· OSTI ID:7065019

Santamato, E; Abbate, G; Maddalena, P

We study the propagation of an elliptically polarized light beam normally incident onto an arbitrarily oriented liquid crystal in steady-state conditions. The Euler-Lagrange equations for the molecular director and the equations describing the evolution of the beam polarization in the birefringent medium are derived from a unique variational principle, which is proved to be consistent with the geometric-optics approximation. The Hamiltonian formulation of the theory is studied in detail. The conservation of total angular momentum and total free energy in the process is derived from Noether's theorem, and the theory of the adiabatic invariants is used to obtain a new proof of Mauguin's theorem of crystal optics. The general analytical solution of the propagation problem is presented for the important case of pure twisted structures. It is proved that two particular solutions exist (called Mauguin's solutions) obeying Mauguin's theorem rigorously. Only these solutions may exhibit the occurrence of the optical Freedericksz transition. In general, multiple optical thresholds are found. An analytical formula to obtain the thresholds is also derived.

• Research Organization: Dipartimento di Fisica Nucleare, Struttura della Materia e Fisica Applicata, Universita degli Studi di Napoli, Padiglione 20, Mostra d'Oltremare, I-80125 Napoli, Italy
• OSTI ID: 7065019
• Journal Information: Phys. Rev. A; (United States), Vol. 38:8
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
36 MATERIALS SCIENCE
LIQUID CRYSTALS
LIGHT TRANSMISSION
MOLECULES
ORIENTATION
POLARIZED BEAMS
ELECTROMAGNETIC FIELDS
INCIDENCE ANGLE
VARIATIONAL METHODS
BEAMS
CRYSTALS
FLUIDS
LIQUIDS
645202* - High Energy Physics- Particle Interactions & Properties-Theoretical- Electromagnetic Interactions & Properties
360602 - Other Materials- Structure & Phase Studies