Optical anisotropy is an inherent property of columnar dielectric films, such as those fabricated by the glancing
angle deposition (GLAD) technique. This process utilizes physical vapor deposition combined with computer-controlled
substrate motion to finely tune the direction of column growth and vital morphological parameters
such as column cross-section and inter-columnar spacing. Control over the anisotropic properties of the porous
film provides an opportunity to design polarization-selective photonic devices and films with improved band
gap properties. Anisotropic defects in multilayer films also result in a polarization-sensitive position of resonant
transmission modes. We employed the finite-difference time-domain and frequency-domain methods to
theoretically analyze and design columnar films with unique band-gap properties. The following morphologies
were considered: (i) S-shaped columnar films with polarization-dependent band-gap position and width. Using
numerical simulations we have shown that the competitive effect of different sources of anisotropy can be used
to engineer photonic band gaps with strong selectivity to linearly-polarized light; (ii) Rugate thin films with an
anisotropic defect, which exhibit resonant mode splitting. Optical devices were fabricated using titanium dioxide
because it has good transparency in the visible range of the optical spectrum and a large bulk refractive index.
Experimental results were compared to simulations to verify the designs and understand the limitations of the
fabrication process.
The fabrication of one dimensional photonic bandgap nanostructures is described and the optical properties of
these structures are examined. Using a deposition technique known as a glancing angle deposition (GLAD),
porous films with a predefined nanoscale geometry are created. Specifically, in the present work we consider
GLAD fabricated thin films characterized by periodically varying refractive index in one-dimension. We
introduce a variety of planar defect layers into the structures and investigate the resulting changes observed in
the photonic bandgap of the system. Theoretical simulation of transmittance spectra of GLAD fabricated films
is performed with the finite-difference time-domain (FDTD) method and the results are compared with
experimental measurements. Modifications of the transmittance spectra are investigated by changing the
geometry of the defect layer and varying the void region effective index. It is shown that the spectral width
and location of states within the bandgap is controlled by the geometry of defect and film microstructure.
Active tunability of the defect states is obtained by considering infilling of the void regions of the structure
with nematic liquid crystals and then analyzing the optical spectrum for various orientations of the liquid
crystal director axis.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.