  Optical frequency conversion has applications ranging from tunable light
sources to telecommunications-band interfaces for quantum information science.
Here, we demonstrate efficient, low-noise frequency conversion on a
nanophotonic chip through four-wave-mixing Bragg scattering in compact
(footprint < 0.5 x 10^-4 cm^2) Si3N4 microring resonators. We investigate three
frequency conversion configurations: (1) spectral translation over a few
nanometers within the 980 nm band, (2) upconversion from 1550 nm to 980 nm, and
(3) downconversion from 980 nm to 1550 nm. With conversion efficiencies ranging
from 25 % for the first process to > 60 % for the last two processes, a signal
conversion bandwidth > 1 GHz, < 60 mW of continuous-wave pump power needed, and
background noise levels between a few fW and a few pW, these devices are
suitable for quantum frequency conversion of single photon states from InAs
quantum dots. Simulations based on coupled mode equations and the
Lugiato-Lefever equation are used to model device performance, and show
quantitative agreement with measurements.
