1. A method of protecting wires of a wire grid polarizer, the method comprising the following steps in the following order:a) providing a wire grid polarizer wafer with:
i) an array of wires located on a surface of a substrate, the array of wires being substantially-parallel and elongated, each wire of the array of wires having a length parallel to the surface of the substrate and a height that is perpendicular to the length and less than 10% of the length, the array of wires including a proximal end of the height closer to the substrate and a distal end of the height farther from the substrate;
ii) a plurality of air-filled channels, including an air-filled channel between adjacent wires of the array of wires; and
iii) a protective-layer located at the distal end of the array of wires and spanning the air-filled channels, the protective-layer providing structural-support for the array of wires and capping the air-filled channels;
b) cutting the wire grid polarizer wafer into multiple wire grid polarizer parts;
c) protecting the array of wires of the wire grid polarizer parts by coating an inside surface of the air-filled channels with a conformal coating having a thickness that is at least 0.1 nm and less than 20 nm and including vapor deposition of a silane chemical including Si(R1)d(R2)e(R3)g and vapor deposition of a phosphonate chemical including (R1)iPO(R4)j(R5)k where d is 1, 2, or 3, e is 1, 2, or 3, g is 0, 1, or 2, and d+e+g=4; i is 1 or 2, j is 1 or 2, k is 0 or 1, and i+j+k=3; each R1 is independently a hydrophobic group; R2 is a silane-reactive-group; each silane-reactive-group is independently selected from: Cl, OR6, OCOR6, N(R6)2, and OH; R4 is a phosphonate-reactive-group; each phosphonate-reactive-group is independently selected from: Cl, OR6, OCOR6, and OH; each R6 is independently an alkyl group, an aryl group, or combinations thereof; each R3, if any, is independently any chemical element or group; and each R5, if any, is independently any chemical element or group; and
d) applying multiple thin-film layers on the protective-layer, the thin-film layers extending continuously across the protective-layer and capable of reducing reflection of incident light on the protective-layer.