  The Kerr nonlinear optical performance of silicon nanowire waveguides
integrated with 2D layered graphene oxide (GO) films is theoretically studied
and optimized based on experimentally measured linear and nonlinear optical
parameters of the GO films. The strong mode overlap between the silicon
nanowires and highly nonlinear GO films yields a significantly enhanced Kerr
nonlinearity for the hybrid waveguides. A detailed analysis for the influence
of waveguide geometry and GO film thickness on the propagation loss, nonlinear
parameter, and nonlinear figure of merit (FOM) is performed. The results show
that the effective nonlinear parameter and nonlinear FOM can be increased by up
to 52 and 79 times relative to bare silicon nanowires, respectively. Self-phase
modulation (SPM)-induced spectral broadening of optical pulses is used as a
benchmark to evaluate the nonlinear performance, examining the tradeoff between
enhancing Kerr nonlinearity and minimizing loss. By optimizing the device
parameters to balance this, a high spectral broadening factor of 27.8 can be
achieved, more than 6 times that achieved in previous experiments. Finally, the
influence of pulse chirp, material anisotropy, and the interplay between
saturable absorption and SPM is also discussed, together with the comparison
between the spectral broadening after going through GO-coated and
graphene-coated silicon waveguides. These results provide useful guidance for
optimizing the Kerr nonlinear optical performance of silicon waveguides
integrated with 2D layered GO films.
