Grating Couplers for Interfacing Ultra-Stable Laser Resonators with Photonic Integrated Chips

Ultra-stable lasers (USLs) are a key enabling technology driving the quantum revolution. They provide the stable frequencies needed for precise interrogation of narrow atomic transitions in atoms or ions. Additionally, they are indispensable for precision measurements in fields such as gravitational wave detection [1] and tests of fundamental physics [2], [3]. Current USLs achieve a relative instability of 4.10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−17</sup>, limited by the fundamental noise of resonator components. The bulky design of conventional USLs, requiring extensive thermal shielding, also necessitates large optical systems for operation [4]. While integrated lasers based on micro-ring resonators offer compact solutions, they still lack the mid- and long-term stability often required [5]. To overcome these limitations, a novel resonator approach leveraging multifunctional mirrors aims to meet the stringent SWaP (size, weight, and power) requirements of the quantum revolution.