Towards an optical frequency standard for the NIST timescale

To correct frequency drifts and random-walk of phase in hydrogen masers and cesium beam clocks that form the timescale at NIST, and to support incorporation of ultra-stable oscillators into the clock ensemble, it is desirable to have an optical frequency standard with high operational uptime with inaccuracy < 1 × 10^-16. Following related work (e.g., [1]), we report progress on development of an optical clock based on the S_1/2 -> D_5/2 transition of a single trapped ⁸⁸Sr⁺ ion. We report ion trapping with a novel manufacturable spherical radio frequency (RF) trap design [2] using a single optical photonic crystal fiber to deliver the necessary wavelengths (all between 400 nm and 1100 nm) to the ion. Operating the trap at the “magic” trap RF drive frequency [3] should enable low systematic uncertainty related to micromotion without complex experimental overhead.

[1] B Jian, J Bernard, M Gertsvolf, P Dubé, Metrologia 60 015007 (2023)

[2] DR Leibrandt, DB Hume, RC Brown, JA Sherman, US Patent 11651949B2 (2023)

[3] A Madej, APS DAMOP 2013 T7-001 (2013).