  We demonstrate wideband integrated photonic circuits in sputter-deposited
aluminum nitride (AlN) thin films. At both near-infrared and visible
wavelengths, we achieve low propagation loss in integrated waveguides and
realize high-quality optical resonators. In the telecoms C-band (1520-1580 nm),
we obtain the highest optical Q factor of 440,000. Critical coupled devices
show extinction ratio above 30 dB. For visible wavelengths (around 770 nm),
intrinsic quality factors in excess of 30,000 is demonstrated. Our work
illustrates the potential of AlN as a low loss material for wideband optical
applications.
