Photonic bandgap properties of nanostructured materials fabricated with glancing angle deposition

Abstract

Glancing angle deposition (GLAD) is a thin film fabrication method providing dynamic control over the internal columnar microstructure of the deposited film. Using the GLAD technique it is possible to control the porosity of the coating allowing precise tailoring of the optical properties. Therefore, in a single material system, the refractive index profile of the film can be engineered to create a variety of multilayer structures. The focus of this research is on the optical properties of these structured thin films. When the structure is periodic, incident radiation is subject to constructive and destructive scattering which lead to photonic bandgap effects. Also of interest are the optical properties of aperiodic systems, such as the Thue-Morse multilayer, which are deterministic but non-periodic. The complex structural correlations in aperiodic systems lead to interesting bandgap-like properties. Applying the GLAD technique, periodic and aperiodic optical lattices are fabricated with titanium dioxide, a dielectric material commonly used in optical coating devices. The bandgap properties of these systems are investigated using transmittance spectroscopy and transfer matrix calculations.