Stabilizing optical microcavities in 3D

Optical (micro-)cavities are the workhorse for studying light-matter interactions with important applications in lasing, sensing, and quantum simulations, to name a few. Open resonators in particular offer great versatility due to their tunability but pose challenges in terms of control. This concerns, on the one hand, the control of their length, and on the other hand, the relative orientation (tilt) of the mirror planes to each other. The latter becomes particularly important when working with optically unstable resonators, such as plane-parallel resonators.
There are numerous strategies to enhance stability using passive techniques, such as material selection, mechanical damping, or thermal compensation. But especially for tuneable microcavities often an active stabilization method with feedback control systems must be employed. Here, we present a novel method for tilt measurement and stabilization using inverse solving of the Schrödinger equation arising in the paraxial description of the cavity modes. Our method enables the highly precise determination of absolute tilt angles, making it suitable for microcavity applications that require the highest level of cavity parallelism.