Liquid crystal light valves driven by photovoltaic fields: Continuation
Abstract
Promising light valving and lensing effects have been identified during the first project period. Test devices, were a thin (30 ?m) liquid crystal (LC) layer was hybridized with a photo generating iron-doped lithium niobate window were exposed with a tightly focused laser beam. The responses inside these devices were investigated by imaging in a modified polarized optical microscope: In these samples, photo generated electric fields were coupled to the LC director, led to director field deformations, and formation of birefringent patterns. Defect formation, micro lensing, and even formation of persistent patterns was possible. The samples were manipulated with micron precision. Numerical simulations were carried out. A model was developed capable to investigate field induced director reorientations (deformed director patterns) and also optical textures. The simulation results were very promising and could already explain the experimental behavior of samples with a nematic LC very well. Various types of responses were found in nematic LCs and studied in depth. For example, the controlled formation of relocatable umbilic defects was observed. In additional experiments, defect free reorientations of the LC director were stimulated in modified samples, were photo generated electric fields were additionally confined to the LC layer by an indium tin oxide coated cover glass. Highly interesting textural changes were found in samples with chiral nematic LCs. Research conducted so far shows, this novel technique to micro manipulate hybridized LC films is very promising. However, the underlying mechanisms (field generation, symmetry constraints) are not yet fully understood. It is therefore proposed to study the nature of field generated optical traps, topological defects, and director reorientation in additional experiments and simulations.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 19, 2018
- Source ID
- FA95501817002
Entities
People
- Alexander Lorenz
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Paderborn