Laser Propagation in Biaxial Liquid Crystal Polymers

Abstract

We examine the propagation of a laser beam through a liquid crystal polymer (LCP) layer using the finite-difference time-domain (FDTD) method. Anchoring conditions on supporting glass plates induce an orientational structure in the LCP between the plates. The orientation can deflect energy away from the direction of propagation of the incident beam when the optical axis or major director of a uniaxial medium is neither parallel nor orthogonal to the incident beam. The maximum energy deflection occurs when the angle between the incident beam and the major director of the orientation is 45 degrees, but for spatially uniform orientations, polarization orthogonal to the plane containing the major director and the propagation direction is unaffected. We investigate how to overcome this by twisting the anchoring alignment on the plates with respect to each other to generate a helical structure in the orientation across the gap to deflect all polarizations. We also examine the difference between the commonly used Leslie-Ericksen theory for the LCP, which assumes a uniaxial orientation, and the more general Doi-Marrucci-Greco orientation tensor model, which allows for both biaxial structures and oblate defect phases.