Chip-based laser with 1-hertz integrated linewidth

Creators: Guo, Joel; McLemore, Charles A.; Xiang, Chao; Lee, Dahyeon; Wu, Lue; Jin, Warren; Kelleher, Megan; Jin, Naijun; Mason, David; Chang, Lin; Feshali, Avi; Paniccia, Mario; Rakich, Peter T.; Vahala, Kerry J.; Diddams, Scott A.; Quinlan, Franklyn; Bowers, John E.

Abstract

Lasers with hertz linewidths at time scales of seconds are critical for metrology, timekeeping, and manipulation of quantum systems. Such frequency stability relies on bulk-optic lasers and reference cavities, where increased size is leveraged to reduce noise but with the trade-off of cost, hand assembly, and limited applications. Alternatively, planar waveguide–based lasers enjoy complementary metal-oxide semiconductor scalability yet are fundamentally limited from achieving hertz linewidths by stochastic noise and thermal sensitivity. In this work, we demonstrate a laser system with a 1-s linewidth of 1.1 Hz and fractional frequency instability below 10⁻¹⁴ to 1 s. This low-noise performance leverages integrated lasers together with an 8-ml vacuum-gap cavity using microfabricated mirrors. All critical components are lithographically defined on planar substrates, holding potential for high-volume manufacturing. Consequently, this work provides an important advance toward compact lasers with hertz linewidths for portable optical clocks, radio frequency photonic oscillators, and related communication and navigation systems.

Additional Information

© 2022 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). We thank A. Ludlow's group (NIST-Boulder) for stable Ytterbium laser reference light; P. Morton (Morton Photonics), J. Peters (UCSB), and D. Kinghorn (Pro Precision Process) for contributions in the design, fabrication, and packaging of the E-DBR laser; and M. Boyd (Vector Atomic) for discussions on optical clocks. Commercial equipment is identified for scientific clarity only and does not represent an endorsement by NIST. This research was supported by DARPA GRYPHON, LUMOS, and APHI contracts HR0011-22-2-0009, HR0011-20-2-0044, and FA9453-19-C-0029 and the NIST on a Chip (NOAC) program. Author contributions: J.E.B., F.Q., and S.A.D. conceived the idea for the project. J.G. and C.A.M. performed the PDH locking experiment and analyzed the data, with assistance from D.L., M.K., and F.Q. L.C. provided logistical support. J.G., C.X., and L.W. performed the self-injection locking experiments with the different FSR Si3N4 resonators. C.X. designed and fabricated the E-DBR laser. W.J., A.F., and M.P. provided the Si3N4 resonators. N.J. and D.M. designed and fabricated the micromirrors. C.A.M. designed and built the μ-FP cavity. J.G. and C.A.M. wrote the manuscript, with input from the other authors. P.T.R., K.J.V., S.A.D., F.Q., and J.E.B. supervised the project. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper. The datasets needed to reproduce the figures are available through Zenodo at https://doi.org/10.5281/zenodo.7017846. Competing interests: J.G., C.A.M., C.X., W.J., L.C., P.T.R., K.J.V., S.A.D., F.Q., and J.E.B. are coinventors on a provisional patent filed by California Institute of Technology (no. 63/299,365, filed 13 January 2022). J.E.B. is a cofounder of Nexus Photonics and Quintessent, which are involved in silicon photonics. The other authors declare that they have no competing interests.

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