A SIMPLE LATERALLY TAPERED WAVE-GUIDE FOR LOW-LOSS COUPLING TO SINGLE-MODE FIBERS

Low-loss coupling between semiconductor photonic devices and single-mode fibers is achieved using a simple InP/InGaAsP tapered waveguide. The proposed simple structure has a small and nearly square guiding core at its output facet. In this structure, the output field has a non-Gaussian profile, but low-loss fiber coupling can be achieved by optimizing the design of the guiding core sizes. The waveguide is composed of a laterally tapered InGaAsP guiding layer and an InP cladding region on an InP substrate, facilitating integration of the waveguide with active devices using conventional processes. Our waveguide is shown to have a total insertion loss of 2.6 dB, including a coupling loss of 0.9 dB and large +/- 2.5 mum misalignment tolerance in lateral and vertical directions with single-mode fibers.