Ultrahigh Q microring resonators using a single-crystal aluminum-nitride-on-sapphire platform

Aluminum-nitride-on-sapphire has recently emerged as a novel low-loss photonics platform for a variety of on-chip electro-optics as well as linear and nonlinear optics applications. In this Letter, we demonstrate ultrahigh quality factor (Q_int) microring resonators using single-crystal aluminum nitride grown on a sapphire substrate with an optimized design and fabrication process. A record high intrinsic Q_int up to 2.8×10⁶ at the wavelength of 1550 nm is achieved with a fully etched structure, indicating a low propagation loss less than 0.13 dB/cm. Such high Q_int aluminum-nitride-on-sapphire resonators with their wide bandgap and electro-optical and nonlinear optical properties is promising for a wide range of low-power and high-power compact on-chip applications over a broad spectral range.