Evanescent Wave Coupling Between Optical Fiber and Planar Optical Waveguide

Transverse coupling between single mode fiber and single mode planar waveguide is analyzed for the first time-to the authors' knowledge-by an improved coupled mode theory (ICMT). The coupling is established via the evanescent part of the modal field propagating in the fiber which penetrates the slab waveguide. The main parameters that characterize the coupling process are calculated. A comparison between the results of the ICMT and those obtained by the usual coupled mode theory reveals an improvement in the accuracy by almost twenty percent