Initial investigation of Moxtek wire grid polarizers composed of Al and coated with SiO2 - SiX - SiO2 (where SiX is used to indicate a Si rich layer whose complete composition is not to be disclosed for proprietary reasons) showed a growth of 3x in the inner (closest to Al) SiO2 layer after baking. Upon removing the X and varying rib composition and layering composition and geometries in 12 sets of before and after samples, no obvious growth was observed. Even baking the original unbaked sample yielded no growth. Our data suggest that the initial conclusion of buried oxide growth was flawed and that the observed changes in optical properties upon baking are either very sensitive to layer thicknesses (smaller than we can confidently observe) or due to some other mechanism. Here we present our sample preparation and analysis using the Focused Ion Beam (FIB), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Xray Spectroscopy (EDXS).

Wire-grid polarizers (WGPs) offer superior extinction, durability, angle of incidence, and heat resistance when compared to traditional organic polarizers. WGPs are found in applications such as high lumen lighting, laser devices, high lumen digital cinema projectors, LED packaging, and other integrated optical applications and are driving the need for over-coatings. Over-coating a WGP has been found to increase lifetime and durability. This research provides lifetime data on coated and uncoated WGPs. WGPs over-coated with 100nm of SiO2, 300nm of MgF2, and with no over-coating were heated to temperatures of 450 ºC, 500 ºC, and 550 ºC and timed until they reached a predetermined optical failure point. The activation energies were calculated by applying the Arrhenius model to the failure data. WGPs with no over-coating were found to have an activation energy ≥ 1.5329 eV, with silicon dioxide an activation energy ≥ 1.7197 eV, and with magnesium fluoride an activation energy ≥ 2.4577 eV. It has been shown that coating a WGP with an over-coating of silicon dioxide or magnesium fluoride slows the oxidation process of the aluminum nano-wires, thus increasing the lifetime of the WGP by 208% and 27,904%, respectively. Parasitic chemical reactions were not found to exist with silicon dioxide or magnesium fluoride when used as an over-coating.