Tapered Silicon Waveguides for Low Insertion Loss Highly-Efficient high-Speed Electronic Variable Optical Attenuators

In this paper we describe our recently developed NVT mode-matching epitaxial adiabatic tapered waveguide technology, and show that it leads to a dramatic reduction of insertion loss in an integrated silicon waveguide. We have introduced the NVT process into a four-channel silicon-on-insulator (SOI) EVOA which relies on current injection to alter the level of free-carrier absorption in the silicon waveguide and thus allows the precise electronic control of optical attenuation.