  Photonic integrated circuits that exploit nonlinear optics in order to
generate and process signals all-optically have achieved performance far
superior to that possible electronically - particularly with respect to speed.
Although silicon-on-insulator has been the leading platform for nonlinear
optics for some time, its high two-photon absorption at telecommunications
wavelengths poses a fundamental limitation. We review the recent achievements
based in new CMOS-compatible platforms that are better suited than SOI for
nonlinear optics, focusing on amorphous silicon and Hydex glass. We highlight
their potential as well as the challenges to achieving practical solutions for
many key applications. These material systems have opened up many new
capabilities such as on-chip optical frequency comb generation and ultrafast
optical pulse generation and measurement.
