Design, Fabrication, and Characterization of a One-Dimensional Polarizing Photonic Crystal

A one-dimensional, single-material polarizing photonic bandgap structure is designed and fabricated using ebeam PVD and oblique angle deposition technique. In order to obtain high- and low-index layers, we deposited alternate layers of titanium dioxide (TiO2) at deposition angles of 0 degrees and 70 degrees on top of a fused silica substrate. This approach is chosen since at deposition angle of zero degree, deposited TiO2 using e-beam PVD, show a negligible birefringence while the obliquely deposited TiO2 acts as a biaxial material with significant birefringent behavior. As a result, deposition of a bilayer film at two angles is analogous to using two different materials with the advantage of simplifying fabrication and modeling this polarizing device. The bandgap of the bilayer structure is modeled in a way that only a specific wavelength with certain polarization, p polarization, could pass through while the s polarization is reflected. For modeling we used Transfer Matrix Method and numerical FDTD analysis to simulate behavior of the ID photonic band gap structure. The simulations produce better than 98% reflection for s polarization and almost no reflection for p polarization for the center wavelength of 632.8 nm. The fabricated device shows 94% reflection for s polarization and less than 6% reflection for p polarization at the red HeNe laser wavelength at an incident angle of 70 degrees. The results demonstrate that a 1D multi-layer photonic crystal, fabricated from a single material, can be designed to selectively reflect or transmit p or s polarization of an incident light beam.