Sculptured porous Bragg Microcavities (BMs) formed by the successive stacking of columnar SiO₂ and TiO₂ thin films with zig-zag columnar microstructure are prepared by glancing angle deposition. These BMs act as wavelength dependent optical retarders. This optical behavior is attributed to a self-structuration mechanism involving a fence-bundling association of nanocolumns as observed by Focused Ion Beam Scanning Electron Microscopy. The retardance of these optically active BMs can be modulated by dynamic infiltration of their open porosity with vapors, liquids or solutions with different refractive indices. The tunable birefringence of these nanostructured photonic systems have been successfully simulated with a simple model that assumes that each layer within the BMs stack has uniaxial birefringence. This type of self-associated nanostructures has been incorporated to microfluidic chips for free label vapor and liquid sensing. Several examples of the detection performance of these chips, working either in reflection or transmission configuration, for the optical characterization of vapor and liquids of different refractive index and aqueous solutions of glucose flowing through the microfluidic chips are described.

Date Published: 30 August 2017
PDF: 13 pages
Proc. SPIE 10356, Nanostructured Thin Films X, 1035603 (30 August 2017); doi: 10.1117/12.2272411

Published in SPIE Proceedings Vol. 10356:
Nanostructured Thin Films X
Yi-Jun Jen; Akhlesh Lakhtakia; Tom G. Mackay, Editor(s)