AVS 53rd International Symposium
    Advanced Surface Engineering Wednesday Sessions
       Session SE1-WeA

Paper SE1-WeA5
Nanoporous Thin Films for Optical Interference Coatings

Wednesday, November 15, 2006, 3:20 pm, Room 2007

Session: Glancing Angle Deposition
Presenter: M.M. Hawkeye, University of Alberta, Canada
Authors: M.M. Hawkeye, University of Alberta, Canada
M.J. Brett, University of Alberta, Canada
Correspondent: Click to Email
Thin films with periodically varying refractive indices display photonic bandgap effects and are commonly used as optical interference filters for a variety of applications. Glancing angle deposition (GLAD) offers a straightforward method for depositing thin films with controlled nanoscale porosity gradients, allowing fabrication of inhomogeneous optical coatings. Thin films of titanium dioxide with sinsuoidal refractive index profiles were deposited by reactive e-beam evaporation and their applicability as optical filters was investigated. We found that a wide range of filter characteristics may be achieved using the GLAD process to control the film porosity. By introducing intentional defects in the sinusoidal index profile, narrow bandpass optical filters are realized. Through modification of the defect parameters, the optical properties of the narrow bandpass may be controlled. Tunability of the filter characteristics such as spectral location, bandwidth, and polarization dependence is demontrated through simulation and experimental results. Apodization of the refractive index profile to reduce the interference sidelobes characteristic of these optical filters is also discussed. The presented work shows the precision of the GLAD technique for fabricating optical interference filters for applications in the visible spectrum.