@article {Newman:19, title = {Architecture for the photonic integration of an optical atomic clock}, journal = {Optica}, volume = {6}, number = {5}, year = {2019}, month = {May}, pages = {680{\textendash}685}, publisher = {Optica Publishing Group}, abstract = {Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities for exploring fundamental physics and enabling new measurements. However, their size and the use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-chip photonics for integration and to reduce component size and complexity, we demonstrate a compact optical-clock architecture. Here a semiconductor laser is stabilized to an optical transition in a microfabricated rubidium vapor cell, and a pair of interlocked Kerr-microresonator frequency combs provide fully coherent optical division of the clock laser to generate an electronic 22\&\#x00A0;GHz clock signal with a fractional frequency instability of one part in 1013. These results demonstrate key concepts of how to use silicon-chip devices in future portable and ultraprecise optical clocks.}, keywords = {frequency combs, Optical clocks, Optical standards, Photonic integration, semiconductor lasers, Tunable diode lasers}, doi = {10.1364/OPTICA.6.000680}, url = {http://opg.optica.org/optica/abstract.cfm?URI=optica-6-5-680}, author = {Zachary L. Newman and Vincent Maurice and Tara Drake and Jordan R. Stone and Travis C. Briles and Daryl T. Spencer and Connor Fredrick and Li, Qing and Daron Westly and B. R. Ilic and Shen, Boqiang and Suh, Myoung-Gyun and Yang, Ki Youl and Cort Johnson and David M. S. Johnson and Leo Hollberg and Kerry J. Vahala and Srinivasan, Kartik and Diddams, Scott A. and John Kitching and Scott B. Papp and Matthew T. Hummon} }