In some embodiments, the present disclosure relates to an integrated chip having an inter-layer dielectric (ILD) structure along a first surface of a substrate having a photodetector. An etch stop layer is over the ILD structure, and a reflector is surrounded by the etch stop layer and the ILD structure. The reflector has a curved surface facing the substrate at a location directly over the photodetector. The curved surface is coupled between a first sidewall and a second sidewall of the reflector. The reflector has larger thicknesses along the first sidewall and the second sidewall than at a center of the reflector between the first sidewall and the second sidewall.