  We demonstrate high optical quality factors in aluminum nitride (AlN)
photonic crystal nanobeam cavities. Suspended AlN photonic crystal nanobeams
are fabricated in sputter-deposited AlN-on-insulator substrates using a
self-protecting release process. Employing one-dimensional photonic crystal
cavities coupled to integrated optical circuits we measure quality factors up
to 146,000. By varying the waveguide-cavity coupling gap, extinction ratios in
excess of 15 dB are obtained. Our results open the door for integrated photonic
bandgap structures made from a low loss, wide-transparency, nonlinear optical
material system.
