High butt-coupling efficiency to single-mode fibers using a 1.55-μm InGaAsP laser integrated with a tapered ridge mode transformer

We demonstrate a tapered ridge mode expanded laser with reduced far-field divergence angles (9.5/spl deg//spl times/22/spl deg/) and improved coupling to cleaved single-mode fibers (SMF) (3.7-dB coupling loss). This device was grown in a single epitaxial growth and was processed using conventional fabrication techniques, thus making it very attractive for low-cost manufacturing. This scheme also represents a general method by which active gain regions can be introduced into passive optical devices like beam splitters and combiners.