We present a fully digital servo optimized for ultra-stable laser frequency stabilization. Experiments such as optical clock experiments can achieve high laser frequency stability, imposing high bandwidth, high precision, and low noise requirements on servo systems. The laser system utilizes the Pound–Drever–Hall method, employing an ultra-stable cavity to generate an error signal for servo input. The input is separated into two independent channels, with one channel featuring high feedback bandwidth and the other channel featuring high gain in the low-frequency domain. The process is fully digitized using field-programmable gate arrays with custom-made infinite impulse response filters and proportional-integral-derivative algorithms. Thanks to the low latency of 120.5 ns and low input noise of 3.22 × 10−12 V2/Hz@1 Hz, our digital servo can easily lock an external-cavity diode laser to a typical ultra-low expansion ultra-stable cavity. The laser system has a fractional frequency stability of 10−16@1s, with the servo electrical noise contributing only 5.54 × 10−18@1s.
REFERENCES
1.
B. C.
Young
, F. C.
Cruz
, W. M.
Itano
, and J. C.
Bergquist
, “Visible lasers with subhertz linewidths
,” Phys. Rev. Lett.
82
, 3799
–3802
(1999
).2.
P.
Majumder
, H.
Yadav
, R.
Tirupathi
, Kamalkant
, S.
Jain
, P.
Yadav
, A.
Ghosh
, A. S.
Deo
, and D.
Singh
, “Advancing frequency locking: Modified FPGA-Guided direct modulation spectroscopy for laser stabilization
,” Opt Laser. Technol.
170
, 110247
(2024
).3.
Y.
Wang
, K.
Wang
, E. F.
Fenton
, Y.-W.
Lin
, K.-K.
Ni
, and J. D.
Hood
, “Reduction of laser intensity noise over 1 MHz band for single atom trapping
,” Opt. Express
28
, 31209
–31215
(2020
).4.
Z.-M.
Shen
, X.-L.
Zhou
, D.-Y.
Huang
, Y.-H.
Pan
, L.
Li
, J.
Wang
, C.-F.
Li
, and G.-C.
Guo
, “Continuously and widely tunable frequency-stabilized laser based on an optical frequency comb
,” Rev. Sci. Instrum.
94
, 023001
(2023
).5.
D. R.
Leibrandt
and J.
Heidecker
, “An open source digital servo for atomic, molecular, and optical physics experiments
,” Rev. Sci. Instrum.
86
, 123115
(2015
).6.
X.-L.
Zhou
, D.-Y.
Huang
, Z.-M.
Shen
, Y.-H.
Pan
, L.
Li
, Y.-J.
Liu
, J.
Wang
, C.-F.
Li
, and G.-C.
Guo
, “Active stabilization of multi-parameter in AMO experiments with a single digital servo
,” Opt Laser. Technol.
167
, 109791
(2023
).7.
N. B.
Jørgensen
, D.
Birkmose
, K.
Trelborg
, L.
Wacker
, N.
Winter
, A. J.
Hilliard
, M. G.
Bason
, and J. J.
Arlt
, “A simple laser locking system based on a field-programmable gate array
,” Rev. Sci. Instrum.
87
, 073106
(2016
).8.
T.
Preuschoff
, M.
Schlosser
, and G.
Birkl
, “Digital laser frequency and intensity stabilization based on the STEMlab platform (originally Red Pitaya)
,” Rev. Sci. Instrum.
91
, 083001
(2020
).9.
T. L.
Nicholson
, M. J.
Martin
, J. R.
Williams
, B. J.
Bloom
, M.
Bishof
, M. D.
Swallows
, S. L.
Campbell
, and J.
Ye
, “Comparison of two independent Sr optical clocks with 1 × 10−17 stability at 103 s
,” Phys. Rev. Lett.
109
, 230801
(2012
).10.
R. X.
Adhikari
, “Gravitational radiation detection with laser interferometry
,” Rev. Mod. Phys.
86
, 121
–151
(2014
).11.
Y.
Zuo
, S.
Dai
, S.
Cao
, W.
Chen
, K.
Liu
, F.
Zheng
, T.
Li
, and F.
Fang
, “Towards a high-performance optical clock based on single 171-Yb ion
,” in 2021 IEEE 6th Optoelectronics Global Conference (OGC)
(IEEE
, 2021
), pp. 91
–93
.12.
A.
Derevianko
, K.
Gibble
, L.
Hollberg
, N. R.
Newbury
, C.
Oates
, M. S.
Safronova
, L. C.
Sinclair
, and N.
Yu
, “Fundamental physics with a state-of-the-art optical clock in space
,” Quantum Sci. Technol.
7
, 044002
(2022
).13.
E. D.
Black
, “An introduction to Pound–Drever–Hall laser frequency stabilization
,” Am. J. Phys.
69
, 79
–87
(2001
).14.
K.
Huang
, H.
Le Jeannic
, J.
Ruaudel
, O.
Morin
, and J.
Laurat
, “Microcontroller-based locking in optics experiments
,” Rev. Sci. Instrum.
85
, 123112
(2014
).15.
M.
Pomponio
, A.
Hati
, and C.
Nelson
, “FPGA-based low-latency digital servo for optical physics experiments
,” in 2020 Joint Conference of the IEEE International Frequency Control Symposium and International Symposium on Applications of Ferroelectrics (IFCS-ISAF)
(IEEE
, 2020
), pp. 1
–2
.16.
S. J.
Yu
, E.
Fajeau
, L. Q.
Liu
, D. J.
Jones
, and K. W.
Madison
, “The performance and limitations of FPGA-based digital servos for atomic, molecular, and optical physics experiments
,” Rev. Sci. Instrum.
89
, 025107
(2018
).17.
V.
Avalos
, X.
Nie
, A.
Yang
, C.
He
, S.
Kumar
, and K.
Dieckmann
, “Field-programmable-gate-array-based digital frequency stabilization of low-phase-noise diode lasers
,” Rev. Sci. Instrum.
94
, 063001
(2023
).18.
J.
Zhang
, X. H.
Shi
, X. Y.
Zeng
, X. L.
Lü
, K.
Deng
, and Z. H.
Lu
, “Characterization of electrical noise limits in ultra-stable laser systems
,” Rev. Sci. Instrum.
87
, 123105
(2016
).19.
X.-Q.
Zhu
, X.-Y.
Cui
, D.-Q.
Kong
, H.-W.
Yu
, X.-M.
Zhai
, M.-Y.
Zheng
, X.-P.
Xie
, Q.
Zhang
, X.
Jiang
, X.-B.
Zhang
, P.
Xu
, H.-N.
Dai
, Y.-A.
Chen
, and J.-W.
Pan
, “An ultrastable 1397-nm laser stabilized by a crystalline-coated room-temperature cavity
,” Rev. Sci. Instrum.
95
, 083002
(2024
).20.
T. Instruments, ADC358x 18-bit 0.5 MSPS to 65 MSPS Low Noise Ultra-low Power ADC, Texas Instruments, rev.a ed. (
2022
).21.
Xilinx, Vivado Design Suite 7 Series FPGA and Zynq 7000 SoC Libraries Guide, Xilinx, UG953 ed. (
2024
).22.
W.-C.
Ji
, B.-W.
Wang
, Y.
Hu
, X.-Y.
Cui
, P.
Xu
, X.
Jiang
, H.-N.
Dai
, and Y.-A.
Chen
, “Characterization of the Pound-Drever-Hall feedback loop in an ultra-stable laser system
,” in CLEO 2024
(Optica Publishing Group
, 2024
), paper JTu2A.21.23.
D.
Allan
, “Statistics of atomic frequency standards
,” Proc. IEEE
54
, 221
–230
(1966
).24.
D.
Allan
, “Time and frequency (time-domain) characterization, estimation, and prediction of precision clocks and oscillators
,” IEEE Trans. Ultrason. Ferroelectrics Freq. Control
34
, 647
–654
(1987
).© 2024 Author(s). Published under an exclusive license by AIP Publishing.
2024
Author(s)
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