Evanescent-Field Excitation and Collection Approach for Waveguide Based Photonic Luminescent Biosensors

A silicon oxynitride channel waveguide based evanescent-field optical transducer is presented for lab-onchip application. The optical biosensor detects luminescent bioanalytes infiltrated within a reactor well realized across the waveguide. As a main novelty, the sensing mechanism proposed makes use of the evanescent-field propagating in the waveguide to both excite and to collect the fluorescent signal. To understand the chip behavior, its design and collection efficiency were analyzed by finite-difference time-domain simulations in comparison with similar structures differing in the bioreactor thickness and thereforein the excitatio n and collection mechanisms. It is demonstrated that the best efficiency and performance are reached for the proposed dual evanescent field approach. Characterization of the optical losses and fluorescencemeasurements from a dye solution infiltrated in the bioreactor well validate the proposed working concept.