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Proceedings Paper

Double-handed circular Bragg reflection bands in chiral thin films
Author(s): Andy C. van Popta; Jeremy C. Sit; Michael J. Brett
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Paper Abstract

Titanium dioxide was evaporated onto rotating substrates at highly oblique deposition angles to create thin films exhibiting a nanostructure which resembles a polygonal helix. Abrupt, periodic rotations of the substrate were used to create triangle, square, pentagon, and star-shaped film morphologies. Experimental optical measurements show that polygonal-helix thin-films exhibit double-handed circular Bragg phenomena. Unlike a standard chiral filter, a polygonal-helix thin-film reflects left-handed circularly polarized light at one frequency band and right-handed circularly polarized light at a second frequency band. The relative wavelength-dependence of the reflection bands is controlled by the angular rotation between arms of a polygonal helix. Spectral-hole polarization filters, produced by adding twist and layer defects to a polygonal helix, are also reported. Twist-defects tend to produce a narrow passband within both circular Bragg reflection bands of a polygonal helix, while a spacing layer defect can be used to produce a passband within only one of the reflection bands.

Paper Details

Date Published: 19 August 2005
PDF: 10 pages
Proc. SPIE 5870, Advances in Thin-Film Coatings for Optical Applications II, 587002 (19 August 2005); doi: 10.1117/12.618039
Show Author Affiliations
Andy C. van Popta, Univ. of Alberta (Canada)
Jeremy C. Sit, Univ. of Alberta (Canada)
Michael J. Brett, Univ. of Alberta (Canada)

Published in SPIE Proceedings Vol. 5870:
Advances in Thin-Film Coatings for Optical Applications II
Michael L. Fulton; Jennifer D. T. Kruschwitz, Editor(s)

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