A multiple quantum well (MQW) superlattice photodetector, is surmounted by a slab of transparent material having an angled surface that extends upward and away from the photodetector, such that incident radiation which is initially normal to the superlattice undergoes total internal reflection at the angled surface and is reflected onto the detector at a substantially non-normal angle. This off-normal angle allows the radiation to be partially absorbed by the detector. A reflection grating is preferably formed on the opposite side of the detector to redirect received radiation back through the MQW superlattice at an altered angle, such that remaining radiation can be absorbed by the detector during the second pass. The detector is formed upon a substrate, with the slab, substrate and quantum wells all preferably formed from the same type of material. Multiple detectors may be formed in an array upon a common substrate, with a slab providing a common reflective surface for the overall array.