A biochip device includes a waveguide, chromophore elements, a diffusing structure, and a sloping surface. The chromophore elements are disposed on a portion of the waveguide and are configured to emit fluorescence in response to excitation by guided light waves transmitted by the waveguide. The diffusing structure is configured to generate guided light waves in the waveguide when illuminated. The sloping surface is sloped relative to a plane of the waveguide and is configured to direct excitation light into the waveguide, and the sloping surface and the waveguide are configured to deflect the excitation light to the diffusing structure to generate guided light waves within the waveguide. The sloping surface may be a face of a prism attached to or integrated with the waveguide, or the sloping surface may be a chamfer formed at an edge of the waveguide.