prospects for classical and quantum optics. Compared with other integrated platforms,
aluminum nitride (AlN) is particularly attractive as it features an enormous bandgap of∼ 6.2
eV and intrinsic χ^(2) and χ^(3) susceptibilities. In this work, we demonstrate a record quality
factor of 2.1× 10^ 5 (optical loss∼ 8 dB/cm) at 390 nm based on single-crystalline AlN
microrings. The low-loss AlN waveguide represents a significant milestone toward UV …