Publication
In this paper, we present the first ultra-low-noise, self-injection locked (SIL) laser with frequency agility based on the monolithic integration of a low-loss silicon nitride (Si3N4) photonic spiral cavity with an aluminum nitride (AlN) actuator. The self-injection locking and stress-optic modulation of the optical cavity demonstrate a fully-integrated, packaged laser featuring frequency noise lower than fiber lasers (3-Hz intrinisic laser linewidth) and high-speed laser frequency modulation with flat frequency actuation bandwidth up to 400-kHz. This is achieved using piezoelectric stress-optic transduction of the entire 5-cm optical cavity, resulting in one of the largest piezoelectric structures, with an area of 19.8 square millimeters, operating at MHz level frequencies. We demonstrate pin-hole-free fabrication of the transducer devices and utilize a novel fabrication process called the “Band-Aid process” which removes unnecessary capacitance and allows for easier packaging and more robust wirebonding.