High-efficiency fiber-to-chip coupling using low-loss tapered single-mode fiber

We report on the wet chemical fabrication of tapered step-index single-mode fibers and the low-loss coupling between these fibers and III-V semiconductor waveguide structures. Nearly adiabatic tapered fibers with an average transformation loss of 0.13 dB and mode field diameters ranging between 10.6 μm and 0.8 μm have been fabricated. Experimentally, tapered fibers have been coupled to 1.55-μm InGaAsP-InP waveguide electroabsorption modulators with a minimum coupling loss of only 1.1 dB.