  We demonstrate second order optical nonlinearity in aluminum nitride on
insulator substrates. Using sputter-deposited aluminum nitride thin films we
realize nanophotonic waveguides coupled to micro-ring resonators that
simultaneously support cavity resonant modes for both visible and IR light. By
using phase matched ring resonators, we achieve efficient second-harmonic
generation and are able to generate up to 0.5uW of visible light on the chip
with a conversion efficiency of -46dB. From the measured response we obtain a
second order non-linear susceptibility (\c{hi}2) of 4.7pm/V. Our platform
provides a viable route for realizing wideband linear and nonlinear optical
devices on a chip.
