Optical modules including focal length adjustment and fabrication of the optical modules

A method of fabricating optical modules, the method comprising:

• providing a wafer/spacer stack attached to a flange focal length correction substrate, wherein the wafer/spacer stack includes a plurality of wafers separated from one another by a first spacer, the wafer/spacer stack being separated from the flange focal length correction substrate by a second spacer, the first and second spacers being composed of a material that is non-transparent to light of a particular wavelength or range of wavelengths, optical elements being disposed on the plurality of wafers to form lens systems, and the wafer/spacer stack including a surface of one of the plurality of wafers farthest from the flange focal length correction substrate;
• forming trenches in respective portions of the wafer/spacer stack, the trenches separating the lens systems from one another, each particular one of the trenches extending from a plane that is flush with the surface of the wafer farthest from the substrate, the trenches extending at least partially into the second spacer that separates the substrate from the wafer/spacer stack;
• injecting a material into the trenches, wherein the injected material is non-transparent to light of the particular wavelength or range of wavelengths, wherein the non-transparent material injected into the trenches substantially fills the trenches at least up to the surface of the wafer farthest from the flange focal length correction substrate;
• and
• adjusting a thickness of one or more regions of the flange focal length correction substrate to provide focal length correction for a respective one or more of the lens systems.