Evanescent coupling is used to couple light from an organic Lambertian emitter into a single-mode planar waveguide. A polymer light emitting diode pumps a photoluminescent layer located directly on top of the waveguide. At the out-coupling grating stage, a fully organic mini-spectrometer compatible with monolithical integration on optical bio chips has been developed. It consists of a single-mode waveguide with integrated diffraction grating and a dense array of polymer photodiodes as sensing element. An overall spectral resolution of down to 5 nm has been achieved with the integrated optoelectronic system. As a proof of principle the fully organic optical device has been used in combination with a fluidic system to demonstrate an absorption-based bio-test with mouse immunoglobulin G. In a further step towards low-cost and disposable lab-on-chip biosensors, the mentioned organic building blocks have been combined with a surface plasmon stack integrated directly onto the single mode waveguide. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 80-87, 2011