  Microresonators on a photonic chip could enhance nonlinear optics effects,
thus are promising for realizing scalable high-efficiency frequency conversion
devices. However, fulfilling phase matching conditions among multiple
wavelengths remains a significant challenge. Here, we present a feasible scheme
for degenerate sum-frequency conversion that only requires the two-mode phase
matching condition. When the drive and the signal are both near resonance to
the same telecom mode, an efficient on-chip photon-number conversion efficiency
upto 42% was achieved, showing a broad tuning bandwidth over 250GHz.
Furthermore, cascaded Pockels and Kerr nonlinear optical effects are observed,
enabling the parametric amplification of the optical signal to a distinct
wavelength in a single device. The scheme demonstrated in this work provides an
alternative approach to realizing high-efficiency frequency conversion and is
promising for future studies on communications, atom clocks, sensing, and
imaging.
