Biosensor including a device base having a sensor array of light sensors and a guide array of light guides. The light guides have input regions that are configured to receive excitation light and light emissions generated by biological or chemical substances. The light guides extend into the device base toward corresponding light sensors and have a filter material. The device base includes device circuitry electrically coupled to the light sensors and configured to transmit data signals. A passivation layer extends over the device base and forms an array of reaction recesses above the light guides. The biosensor also includes peripheral crosstalk shields that at least partially surround corresponding light guides of the guide array to reduce optical crosstalk between adjacent light sensors.