AVS 53rd International Symposium
    Advanced Surface Engineering Wednesday Sessions
       Session SE-WeM

Paper SE-WeM13
Circular Bragg Reflectors Formed by Glancing Angle Deposition of Helically-Structured Thin Films

Wednesday, November 15, 2006, 12:00 pm, Room 2007

Session: Glancing Angle Deposition
Presenter: A.C. van Popta, University of Alberta, Canada
Authors: A.C. van Popta, University of Alberta, Canada
J.C. Sit, University of Alberta, Canada
M.J. Brett, University of Alberta, Canada
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The glancing angle deposition (GLAD) process is capable of generating thin films with anisotropic physical properties that can be manipulated to produce unique materials and devices. For instance, substrate rotation can be used to shape the columnar morphology of a GLAD film into helical structures that exhibit circular Bragg effects similar to cholesteric liquid crystals. At extremely oblique deposition angles, the high porosity of a helically-structured thin film can be used to create electrically-addressable hybrid optical materials by embedding liquid crystals within the pores of the thin film matrix, while less oblique deposition angles result in helical films that exhibit stronger circular Bragg reflections due to diminished scattering and enhanced form birefringence. By replacing the continuous rotation of the local optical axis in a helical GLAD film with discrete incremental rotations, it is possible to form polygonal helix structures that exhibit both left-handed and right-handed circular reflection bands, and introducing a twist defect or spacing layer defect will lead to the formation of narrow bandpass filters. This work will highlight experimental results involving helically-structured inorganic thin films produced by GLAD, including novel deposition schemes to control the form birefringence of a GLAD film, post-processing steps for enhancing optical anisotropies in GLAD films, and methods for depositing improved chiral filter designs.