An apparatus with a first photodetector and a second photodetector is provided. The apparatus is configured to receive light, and the first photodetector is configured to detect a first portion of the light. The first photodetector and the second photodetector are in a stacked arrangement and the apparatus is configured to pass a second portion of the light through the first photodetector to the second photodetector. The apparatus further includes an optical blocking filter configured to filter the second portion of the light prior to the second portion of the light arriving at the second photodetector.