Optically induced orientational transitions in nematics with planar alignment

TL;DR

This paper theoretically investigates how linearly polarized light induces orientational transitions in planar nematic liquid crystals, revealing lower thresholds for transitions and complex dynamical states depending on layer thickness.

Contribution

It provides a detailed theoretical analysis of optically induced transitions in nematics, including threshold calculations and stability of various director configurations.

Findings

Lower than expected threshold for Freedericksz transition.

Existence of stationary and oscillatory director states.

Secondary bifurcation leading to distorted stationary states.

Abstract

Theoretical study of dynamical phenomena induced by a linearly polarized plane wave incident perpendicularly on a planar aligned nematic layer with the light intensity as the control parameter is reported. We find the threshold of the Optically Induced Freedericksz Transition for the planar state as a function of the problem parameters. It occurs that the threshold is substantially lower than that expected before. Above the primary instability the director settles either to a stationary or to an oscillatory states depending on a thickness of the layer. These states become unstable at a secondary threshold through a heteroclinic bifurcation and the director settles to a new stationary distorted state.