Laser cooling 88Sr to microkelvin temperature with an integrated-photonics system

Published

April 19, 2024

Author(s)

Andrew Ferdinand, Zheng Luo, Sindhu Jammi, Zachary Newman, Grisha Spektor, Okan Koksal, Akash Rakholia, Daniel Sheredy, Parth Patel, Travis Briles, Wenqi Zhu, Martin Machai Boyd, Amit Agrawal, Scott Papp

Abstract

We report on experiments generating a magneto-optical trap (MOT) of 88-strontium (88Sr) atoms at microkelvin temperature, using integrated-photonics devices. With metasurface optics integrated on a fused-silica substrate, we generate six-beam, circularly polarized, counter-propagating MOTs on the blue broad-line, 461 nm, and red narrow-line, 689 nm, Sr cooling transitions without bulk optics. By use of a diverging beam configuration, we create up to 10 mm diameter MOT beams at the trapping location. To frequency stabilize and linewidth narrow the cooling lasers, we use fiber-packaged, integrated nonlinear waveguides to spectrally broaden a frequency comb. The ultra-coherent supercontinuum of the waveguides covers 650 nm to 2500 nm, enabling phase locks of the cooling lasers to hertz level linewidth. Our work highlights the possibility to simplify the preparation of an ultracold 88Sr gas for an optical-lattice clock with photonic devices. By implementing a timing sequence for control of the MOT lasers and the quadrupole magnetic-field gradient, we collect atoms directly from a thermal beam into the blue MOT and continuously cool into a red MOT with dynamic detuning and intensity control. There, the red MOT temperature is as low as 2⁢K and the overall transfer efficiency up to 16 %. We characterize this sequence, including an intermediate red MOT with modulated detuning. Our experiments demonstrate an integrated photonics system capable of cooling alkaline-earth gases to microkelvin temperature with sufficient transfer efficiencies for adoption in scalable optical clocks and quantum sensors.

Citation

Physical Review Letters

Pub Type

Journals

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Keywords

Strontium, optical lattice clocks, integrated photonics, laser cooling, metasurface optics

Citation

Ferdinand, A. , Luo, Z. , Jammi, S. , Newman, Z. , Spektor, G. , Koksal, O. , Rakholia, A. , Sheredy, D. , Patel, P. , Briles, T. , Zhu, W. , Boyd, M. , Agrawal, A. and Papp, S. (2024), Laser cooling 88Sr to microkelvin temperature with an integrated-photonics system, Physical Review Letters, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957750 (Accessed April 29, 2025)