Graphene oxide films integrated with nanowires and ring resonators to
enhance nonlinear optics
Abstract
We report enhanced nonlinear optics in nanowires, waveguides, and ring
resonators by introducing layered two-dimensional (2D) graphene oxide
(GO) films through experimental demonstration. The GO films are
integrated on silicon-on-insulator nanowires (SOI), high index doped
silica glass, and silicon nitride (SiN) waveguides and microring
resonators (MRRs), to demonstrate an improved optical nonlinearity
including Kerr nonlinearity and four-wave mixing (FWM). By using a
large-area, transfer-free, layer-by-layer GO coating method with
photolithography and lift-off processes, we integrate GO films on these
complementary metal-oxide-semiconductor (CMOS)-compatible devices. For
SOI nanowires, significant spectral broadening of optical pulses in
GO-coated SOI nanowires induced by self-phase modulation (SPM) is
observed, achieving a high spectral broadening factor of 4.34 for a
device with a patterned film including 10 layers of GO. A significant
enhancement in the nonlinear figure of merit (FOM) for silicon nanowires
by a factor of 20 is also achieved, resulting in a FOM > 5.
For Hydex and SiN waveguides, enhanced FWM in the GO-coated waveguides
is achieved, where conversion efficiency (CE) enhancements of up to 6.9
dB and 9.1 dB relative to the uncoated waveguides. For MRRs, an increase
of up to ~10.3 dB in the FWM CE is achieved due to the
resonant enhancement effect. These results reveal the strong potential
of GO films to improve the nonlinear optics of nanowires, waveguides,
and ring resonators.