Optical materials and devices fabricated by glancing angle deposition

Glancing angle deposition (GLAD) is a physical vapour deposition technique used to create porous thin films that are characterized by a columnar nanostructure. Two advantages that GLAD provides to optical coating design are the ability to create form birefringent thin films and control over the effective refractive index of a thin film. Methods for improving form birefringence in titanium dioxide thin films by combining GLAD and post-deposition thermal annealing were investigated. The GLAD technique was extended to indium tin oxide (ITO), a transparent conductive oxide used extensively in flat panel displays. Characterization of nanostructured ITO thin films revealed significant transparency, conductivity, and birefringence, and the capacity to align liquid crystals in the twisted nematic phase utilized in many liquid crystal displays. The capability for GLAD to control the orientation and magnitude of the local birefringence within a stratified thin film was used to fabricate a series of chiral optical filters that differentiate between circular polarization states of light. Modifications to the physical morphology and chemical composition of helical thin films were studied to determine how deposition parameters can be optimized to improve circular birefringence. Characterization of a helical bilayer exceeding the 50% reflectance limit inherent to cholesteric liquid crystals, the formation of polygonal helix thin films, and a method for reducing interference sidelobes neighbouring the circular Bragg reflection band are also presented.;Modulation of the deposition angle was used to create periodic gradients in the effective refractive index of a thin film. Rugate-style optical interference filters were fabricated using TiO2 and ITO, and narrow bandpass filters were created by adding a spacing-layer or phase-shift defect to the sinusoidal refractive index profile of the thin film. The narrow bandpass filters were also used to build and test a rapid-response relative humidity sensor and assess the use of a hydrophobic chemical functionalization to stabilize the optical properties of porous GLAD thin films.