Architecture for the photonic integration of an optical atomic clock
Zachary L. Newman, Vincent N. Maurice, Tara E. Drake, Jordan R. Stone, Travis Briles, Daryl T. Spencer II, Connor D. Fredrick, Qing Li, Daron A. Westly, Bojan R. Ilic, B. Shen, M.-G Suh, K. Y. Yang, C Johnson, D.M. S. Johnson, Leo Hollberg, K. Vahala, Kartik A. Srinivasan, Scott A. Diddams, John E. Kitching, Scott B. Papp, Matthew T. Hummon
Optical atomic clocks, which rely on high-frequency, narrow-line optical transitions to stabilize a clock laser, outperform their microwave counterparts by several orders of magnitude due to their inherently large quality factors. Optical clocks based on laser-cooled atoms have demonstrated fractional instabilities at the 10−18 level, setting stringent new limits on tests of fundamental physics and may eventually replace microwave clocks in global timekeeping and navigation and the definition of the SI second. Despite their excellent performance, optical clocks are almost exclusively operated by metrological institutions and universities due to their large size and complexity. Here, we demonstrate a low-power, chip-scale optical clock based on the two-photon transition in rubidium-87 in a thermal vapor cell with an instability of 1.7x10−13 at 4000 s. We convert the rubidium-stabilized clock laser to the microwave-frequency domain using a pair of Kerr-microresonator optical frequency combs, providing a path toward commercially viable, compact optical clocks.