Spontaneous Raman scattering in ultrasmall silicon waveguides.

We report spontaneous Raman scattering at 1550 nm in ultrasmall silicon-on-insulator (SOI) strip waveguides of 0.098-microm2 cross-sectional area. The submicrometer-scale dimensions provide tight optical confinement and, hence, highly efficient Raman scattering with milliwatt-level cw pump powers. The prospect of Raman amplification in such a deeply scaled-down waveguide device in the presence of various loss mechanisms, particularly free-carrier loss that arises from two-photon absorption, is discussed, and the feasibility of high-gain SOI-based fully integrated optical amplifiers is shown.