New directions for high-Q integrated photonics

High-Q microresonators provide access to nonlinear optical phenomena at milli-Watt power levels. And the resulting device functions, now in miniature form, are paving the way to integrated optical systems for sensing, metrology, spectroscopy, microwave generation, time keeping and data transmission. Once discrete and reliant upon specialized processing techniques for optical loss reduction, high-Q microresonators are today planar, capable of integration and in some cases fabricated on CMOS foundry lines. After a brief overview of their history and early nonlinear optical demonstrations, Vahala will focus on recent progress using the ultra-low loss silicon nitride system. Besides its well-known advantages for photonic integration, resonators in this system access nonlinear optical phenomena at power levels readily available from III-V semiconductor lasers. Generation of both bright and dark pulse microcombs and related applications will be discussed. Also, the photo galvanic effect in silicon nitride and its application to generate high-coherent visible and near visible light will be described.