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-on-chip 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 therefore in the excitation 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 fluorescence measurements from a dye solution infiltrated in the bioreactor well validate the proposed working concept.