Design of strip-loaded optical waveguides for low-loss coupling to optical fibers

Mismatch between the fundamental mode of a waveguide and that of an attached optical fiber may cause a significant loss of power in a guided-wave structure. These losses can be minimized, however, by proper shaping of the waveguide mode through judicious choice of dimensions and refractive indexes. It is shown by computer modeling and qualitative arguments that coupling losses between standard optical fibers (5-10-μm modal diameter) and strip-loaded waveguides constructed of GaAs/AlGaAs may be reduced to less than 10% at each facet. A wavelength of 0.85 μm is used as a specific example, with modal shapes explored systematically for a series of different waveguide structures