  Optical parametric amplification (OPA) represents a powerful solution to
achieve broadband amplification in wavelength ranges beyond the scope of
conventional gain media, for generating high-power optical pulses, optical
microcombs, entangled photon pairs and a wide range of other applications.
Here, we demonstrate optical parametric amplifiers based on silicon nitride
(Si3N4) waveguides integrated with two-dimensional (2D) layered graphene oxide
(GO) films. We achieve precise control over the thickness, length, and position
of the GO films using a transfer-free, layer-by-layer coating method combined
with accurate window opening in the chip cladding using photolithography.
Detailed OPA measurements with a pulsed pump for the fabricated devices with
different GO film thicknesses and lengths show a maximum parametric gain of
~24.0 dB, representing a ~12.2 dB improvement relative to the device without
GO. We perform a theoretical analysis of the device performance, achieving good
agreement with experiment and showing that there is substantial room for
further improvement. This work represents the first demonstration of
integrating 2D materials on chips to enhance the OPA performance, providing a
new way of achieving high performance photonic integrated OPA by incorporating
2D materials.
