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 semiconduc tor waveguide structures. Nearly adiabatic tapered fibers with an average t ransformation loss of 0.13dB and mode field diameters ranging between 10.6 mu m and 0.8 mu m have been fabricated. Experimentally, tapered fibers have been coupled to 1.55-mu m InGaAsP-InP waveguide electroabsorption modulato rs with a minimum coupling loss of only 1.1 dB.