THE REALIZATION OF AN INTEGRATED MACH-ZEHNDER WAVE-GUIDE IMMUNOSENSORIN SILICON TECHNOLOGY

We describe the realization of a symmetric integrated channel waveguid e Mach-Zehnder sensor which uses the evanescent field to detect small refractive-index changes (Delta n(min) approximate to 1 x 10(-4)) near the guiding-layer surface. This guiding layer consists of ridge struc tures with a height of 3 nm and a width of 4 mu m made in Si3N4. This layer has a thickness of 100 nm. The sensor device has been tested wit h glucose solutions of different bulk refractive indices. Results of a slab-model calculation are in good agreement with obtained experiment al results. The feasibility of applying this sensor for immunosensing, detecting directly the binding of antigen to an antibody receptor sur face, is shown with antibody-antigen binding experiments. (C) 1997 Els evier Science S.A.