A biosensor is provided including a detection device and a flow cell mounted to the detection device. The detection device has a detector surface with a plurality of reaction sites. The detection device also includes a filter layer that is configured to at least one of (a) filter unwanted excitation light signals; (b) direct emission signals from a designated reaction site toward one or more associated light detectors that are configured to detect the emission signals from the designated reaction site; or (c) block or prevent detection of crosstalk emission signals from adjacent reaction sites.