Multifunctional collimator for contact image sensors

Disclosed is a method to fabricate a multifunctional collimator structure In one embodiment, an optical collimator, includes: a dielectric layer; a substrate; and a plurality of via holes, wherein the dielectric layer is formed over the substrate, wherein the plurality of via holes are configured as an array along a lateral direction of a first surface of the dielectric layer, wherein each of the plurality of via holes extends through the dielectric layer and the substrate from the first surface of the dielectric layer to a second surface of the substrate in a vertical direction, wherein the substrate has a bulk impurity doping concentration equal to or greater than 1×1019 per cubic centimeter (cm−3) and a first thickness, and wherein the bulk impurity doping concentration and the first thickness of the substrate are configured so as to allow the optical collimator to filter light in a range of wavelengths.