One innovation includes an IR sensor having an array of sensor pixels to convert light into current, each sensor pixel of the array including a photodetector region, a lens configured to focus light into the photodetector region, the lens adjacent to the photodetector region so light propagates through the lens and into the photodetector region, and a substrate disposed with photodetector region between the substrate and the lens, the substrate having one or more transistors formed therein. The sensor also includes reflective structures positioned between at least a portion of the substrate and at least a portion of the photodetector region and such that at least a portion of the photodetector region is between the one or more reflective structures and the lens, the one or more reflective structures configured to reflect the light that has passed through at least a portion of the photodetector region into the photodetector region.