Transforming silicon into a high performing in tegrated nonlinear
photonics platform by integrati on with 2D graphene oxide films
Abstract
Layered two-dimensional (2D) GO films are integrated with
silicon-on-insulator (SOI) nanowire waveguides to experimentally
demonstrate an enhanced Kerr nonlinearity, observed through self-phase
modulation (SPM). The GO films are integrated with SOI nanowires using a
large-area, transfer-free, layer-by-layer coating method that yields
precise control of the film thickness. The film placement and coating
length are controlled by opening windows in the silica cladding of the
SOI nanowires. Owing to the strong mode overlap between the SOI
nanowires and the highly nonlinear GO films, the Kerr nonlinearity of
the hybrid waveguides is significantly enhanced. Detailed SPM
measurements using picosecond optical pulses show significant spectral
broadening enhancement for SOI nanowires coated with 2.2-mm-long films
of 1−3 layers of GO, and 0.4-mm-long films with 5−20 layers of GO. By
fitting the experimental results with theory, the dependence of GO’s
n2 on layer number and pulse energy is obtained,
showing interesting physical insights and trends of the layered GO films
from 2D monolayers to quasi bulk-like behavior. Finally, we show that by
coating SOI nanowires with GO films the effective nonlinear parameter of
SOI nanowires is increased 16 fold, with the effective nonlinear figure
of merit (FOM) increasing by about 20 times to FOM > 5.
These results reveal the strong potential of using layered GO films to
improve the Kerr nonlinear optical performance of silicon photonic
devices.