Reduced coupling loss using a tapered-rib adiabatic-following fiber coupler

We present the design and experimental demonstration of a tapered-rib adiabatic-following fiber coupler (TRAFFIC). This device is an adaptation of a Shani-Henry mode converter fabricated in (Al)GaAs and designed to increase the coupling efficiency of conventional optical fibers to tightly-confined semiconductor rib waveguide devices. This approach offers the potential of significantly reducing fiber butt coupling losses from the typical values of 7 to 10 dB to values of <1 dB. This long-standing packaging problem is one of the major impediments to the widespread acceptance of semiconductor-based optoelectronics. Moreover, the design can be implemented with minimal increase in fabrication complexity since it uses only a straightforward modification to epitaxial growth, and one additional lithography and etching step.