Just as integrated circuit technology provided a concrete basis for the microelectronics revolution, it is now poised to usher disruptive advances in photonics. Integrated photonic systems have the potential to revolutionize metrology, communication, molecular sensing, computing and atomic-photonic interfaces.
For decades, various photonic hardware has relied on discrete (non-integrable) optical components or even free-space optics. In particular, optical cavities are prevalent in many applications and thus bridging the discrete device functions with photonic integrated circuits has been a priority for developing scalable photonic systems. In this talk, I will present integrated optical cavities with a record-high quality factor, enabling co-integration of III-V laser sources with frequency comb and low-noise microcavity laser. These integrated devices were assembled to large-scale photonic systems including the first chip-scale demonstrations of an optical frequency synthesizer and atomic clock . In addition, I will discuss a sequence of experiments on the development of integrated nonlinear photonics for the visible and ultraviolet regimes .
Accelerating the progress of photonic integration is now facing a new outstanding challenge – the design complexity and requirements vastly increase as photonic systems scale up. Photonics research needs a design method capable of optimizing device-level structures and large-scale system architecture based on user specifications. Combining physics simulations, optimization, and machine learning offers a new approach to inverse-designing and implementing photonic integrated circuits with novel functionalities, compact footprint, and high efficiencies. I will introduce demonstrated devices in silicon, diamond, and silicon carbide – including a nonreciprocal pulse router for chip-scale LiDAR, integrated particle accelerator, and quantum emitter-photon interfaces .
Finally, I will present our ongoing work on inverse-designed optical interconnects and photonic switches, and conclude my talk with an outlook on the potential of inverse-designed photonics to deliver miniaturized system packages for various applications.
 K. Yang et al., Nat. Photon. 12, 297 – 302 (2018); D.T. Spencer et al., Nature 557, 81 – 85 (2018).
 K. Yang et al., Nat. Photon. 10, 316 – 320 (2016); D.Y. Oh, K. Yang et al., Nat. Commun. 8, 13922 (2017).
 K. Yang et al., Nat. Photon. (in press); N.V. Sapra, K. Yang et al., Science 367, 79 – 83 (2020).
Kiyoul Yang is currently a Postdoctoral Scholar in the Nanoscale and Quantum Photonic Laboratory at Stanford University. He received his PhD degree in Electrical Engineering from the California Institute of Technology in 2018. His research involves integrated silicon photonics, nonlinear optics, laser physics and inverse design, with a focus on photonic hardware implementation for scientific studies and technological applications. He is a recipient of the Caltech Atwood fellowship and Stanford Nano- & Quantum science & engineering postdoctoral fellowship, and serves on the technical program committee of the IEEE Photonic Conference.