Light, such as from an analyte-wavelength converter or other optical sensor, is propagated to a detector or transmission structure with an entry surface and with output positions such as in an exit surface. For example, the position of light output by such a detector can be used to detect presence of an analyte such as a biomolecule or chemical. Or relative quantities of photons provided at positions of the exit surface can indicate analyte information such as presence, absence, quantity, or concentration. The detector or transmission structure can have a laterally varying energy transmission function, such as with a constant gradient or a step-like gradient. At the exit surface of the transmission structure, a photosensor array or position sensor can sense transmitted light or output photons, and, in response, circuitry can provide signals indicating the analyte information.