In integrated optics, it is very important to provide efficient optical coupling between fibers and waveguide devices. In this letter, we propose a fiber-waveguide coupler, whose guide width varies in propagation direction, and show its better coupling behavior than an uniform coupler.

A simple and practically accurate method for studying rectangular dielectric waveguides is proposed. This method can provide good evaluations of propagation constant and field distribution of the waveguides by analyzing improved equivalent guide models. In this paper, it is applied in studying a novel taper-formed waveguides system. The waveguides system was experimentally demonstrated of being advantageous in its lightwave transmission characteristics. Experimentally obtained results exhibited good agreement with the performances predicted by the system numerical analyses using the proposed waveguide study technique.