Abstract
Si has large 3rd-order nonlinearity with excellent material transparency ranging from near-infrared (NIR)
to mid-infrared (MIR) regions. With the recent progress of Si photonics technology, various functional
devices applying the nonlinear optical effect have contributed to each field from basic science to industrial
applications. In the first half of this paper, we review the recent advances by the use of the outstanding
material nature of Si in MIR. Our novel suspended nonlinear Si waveguide enables a broadband
spectrum generation that covers the MIR range. In the second half, we apply Si to a versatile
hybrid photonic integration platform to further enhance optical nonlinearity with graphene, which has
recently been recognized as an ultimately high nonlinear material.
