Abstract: The present disclosure describes a system for analyzing biological samples. The system includes an optical waveguide. The optical waveguide includes a first end and a second end. The optical waveguide is configured to receive an excitation light at the first end. The optical waveguide further includes a first light-guiding layer disposed between the first end and the second end. The first light-guiding layer is configured to direct, at least in part, the received excitation light toward the second end of the optical waveguide along a longitudinal direction of the optical waveguide. The optical waveguide further includes a fluidic reaction channel bounded in part by the first light-guiding layer of the optical waveguide, which delivers the excitation light to biological samples disposed in the fluidic reaction channel. The system further includes a backside illumination based image sensor.