Resonant mode excitation in multimode optical waveguide

We studied a planar dielectric waveguide with a surface relief diffraction grating on it. Such a system has a variety of applications including optical sensors, filters, couplers, splitters, and switches. We focused on relatively thick (600um) multimode waveguides with high mode density. Most optical phenomena in such waveguides are well described in geometrical optics. However, we developed a wave theory that predicts the possibility of excitation of only one selected mode. We have investigated such a possibility theoretically and experimentally. Using a monochromatic laser beam with an optimized spatial profile, we demonstrated separate excitation of selected modes in the high-quality Corning glass waveguide supporting 3258 modes.