Kerry Vahala has pioneered nonlinear optics in high-Q optical micro resonators. His research group has launched many of the areas of study in this field and invented optical resonators that hold the record for highest optical Q on a semiconductor chip. Vahala has applied these devices to a wide range of nonlinear phenomena and applications. This includes the first demonstration of parametric oscillation and cascaded four-wave mixing in a micro cavity - the central regeneration mechanisms for frequency micro combs; electro-optical frequency division - used in the most stable commercial K-band oscillators; and the first observation of dynamic back action in cavity optomechanical systems.