Zhou, WeiminCahill, JamesNi, Jimmy H.Deloach, AndrewCho, Sang-YeonAnderson, StephenMahmood, TanvirSykes, PatrickSarney, Wendy L.Leff, Asher C.2021-03-252021-03-252021-02-27Weimin Zhou, James Cahill, Jimmy H. Ni, Andrew Deloach, Sang-Yeon Cho, Stephen Anderson, Tanvir Mahmood, Patrick Sykes, Wendy L. Sarney, and Asher C. Leff "Developing a chip-scale optical clock," Optical Engineering 60(2), 027107 (27 February 2021). https://doi.org/10.1117/1.OE.60.2.027107https://doi.org/10.1117/1.OE.60.2.027107http://hdl.handle.net/11603/21210We report our in-house R&D efforts of designing and developing key integrated photonic devices and technologies for a chip-scale optical oscillator and/or clock. This would provide precision sources to RF-photonic systems. It could also be the basic building block for a photonic technology to provide positioning, navigation, and timing as well as 5G networks. Recently, optical frequency comb (OFC)-based timing systems have been demonstrated for ultra-precision time transfer. Our goal is to develop a semiconductor-based, integrated photonic chip to reduce the size, weight, and power consumption, and cost of these systems. Our approach is to use a self-referenced interferometric locking circuit to provide short-term stabilization to a micro-resonator-based OFC. For long-term stabilization, we use an epsilon-near-zero (ENZ) metamaterial to design an environment-insensitive cavity/resonator, thereby enabling a chip-scale optical long-holdover clock.14 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.Public Domain Mark 1.0This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. LawText