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Atomic and Molecular Optics|20 Article(s)
Magnetic field stabilization system designed for the cold-atom coherent population-trapping clock
Chang Zhan, Zhu Ma, Jiatao Wu, Maojie Li, Chengyin Han, Bo Lu, and Chaohong Lee
Accurate control of magnetic fields is crucial for cold-atom experiments, often necessitating custom-designed control systems due to limitations in commercially available power supplies. Here, we demonstrate precise and flexible control of a static magnetic field by employing a field-programmable gate array and a feedback loop. This setup enables us to maintain exceptionally stable current with a fractional stability of 1 ppm within 30 s. The error signal of the feedback loop exhibited a noise level of 10-5 A·Hz-1/2 for control bandwidths below 10 kHz. Utilizing this precise magnetic field control system, we investigate the second-order Zeeman shift in the context of cold-atom coherent population-trapping (CPT) clocks. Our analysis reveals the second-order Zeeman coefficient to be 574.21 Hz/G2, with an uncertainty of 1.36 Hz/G2. Consequently, the magnetic field stabilization system we developed allows us to achieve a second-order Zeeman shift below 10-14, surpassing the long-term stability of current cold-atom CPT clocks. Accurate control of magnetic fields is crucial for cold-atom experiments, often necessitating custom-designed control systems due to limitations in commercially available power supplies. Here, we demonstrate precise and flexible control of a static magnetic field by employing a field-programmable gate array and a feedback loop. This setup enables us to maintain exceptionally stable current with a fractional stability of 1 ppm within 30 s. The error signal of the feedback loop exhibited a noise level of 10-5 A·Hz-1/2 for control bandwidths below 10 kHz. Utilizing this precise magnetic field control system, we investigate the second-order Zeeman shift in the context of cold-atom coherent population-trapping (CPT) clocks. Our analysis reveals the second-order Zeeman coefficient to be 574.21 Hz/G2, with an uncertainty of 1.36 Hz/G2. Consequently, the magnetic field stabilization system we developed allows us to achieve a second-order Zeeman shift below 10-14, surpassing the long-term stability of current cold-atom CPT clocks.
Chinese Optics Letters
- Publication Date: Aug. 13, 2024
- Vol. 22, Issue 8, 080202 (2024)
Tunable off-resonant Rydberg microwave frequency comb spectroscopy based on metawaveguide coupled Rydberg atoms|Editors' Pick
Lihua Zhang, Zongkai Liu, Bang Liu, Qifeng Wang, Yu Ma, Tianyu Han, Zhengyuan Zhang, Hanchao Chen, Shiyao Shao, Qing Li, Jun Zhang, Dongsheng Ding, and Baosen Shi
Studying Rydberg microwave frequency comb (MFC) spectroscopy helps increase the working bandwidth of the Rydberg receiver. This Letter demonstrates off-resonant Rydberg MFC spectroscopy in a meta-waveguide-coupled Rydberg atomic system. An off-resonant MFC field couples with the Rydberg atoms through a meta-waveguide. The system can receive the microwave field in the working band from 0.5 GHz to 13.5 GHz, and the MFC spectroscopy covers a span of 36 MHz at three different arbitrarily-chosen frequencies of 2 GHz, 3 GHz, and 5.8 GHz. The MFC spectrum that covers a wide range of 125 MHz is also verified. This work is significant for tunable wide-band instant microwave signal detection in the Rydberg atomic system, which is useful in microwave frequency metrology, communication, and radar. Studying Rydberg microwave frequency comb (MFC) spectroscopy helps increase the working bandwidth of the Rydberg receiver. This Letter demonstrates off-resonant Rydberg MFC spectroscopy in a meta-waveguide-coupled Rydberg atomic system. An off-resonant MFC field couples with the Rydberg atoms through a meta-waveguide. The system can receive the microwave field in the working band from 0.5 GHz to 13.5 GHz, and the MFC spectroscopy covers a span of 36 MHz at three different arbitrarily-chosen frequencies of 2 GHz, 3 GHz, and 5.8 GHz. The MFC spectrum that covers a wide range of 125 MHz is also verified. This work is significant for tunable wide-band instant microwave signal detection in the Rydberg atomic system, which is useful in microwave frequency metrology, communication, and radar.
Chinese Optics Letters
- Publication Date: Aug. 13, 2024
- Vol. 22, Issue 8, 080201 (2024)
Magneto-optical isotope enrichment of potassium-40 with transverse cooling
Shangjin Li, Zixuan Zeng, and Bo Yan
Isotope shifts among different isotopes can be effectively addressed using narrow-linewidth lasers, facilitating laser isotope separation and achieving significant enrichment at a single stage. The separation of potassium isotopes, employing optical pumping and magnetic deflection, has proven to be efficient. To further improve the enrichment of 40K, we introduce 2D transverse cooling to minimize the divergence angle. Through this modification, we demonstrate enrichment of 40K, elevating it from 0.012% to 12%–20%. This represents an enrichment increase by three orders of magnitude, surpassing our previous result by one order. Our method is particularly well-suited for isotope enrichment of elements with extremely low abundance. Isotope shifts among different isotopes can be effectively addressed using narrow-linewidth lasers, facilitating laser isotope separation and achieving significant enrichment at a single stage. The separation of potassium isotopes, employing optical pumping and magnetic deflection, has proven to be efficient. To further improve the enrichment of 40K, we introduce 2D transverse cooling to minimize the divergence angle. Through this modification, we demonstrate enrichment of 40K, elevating it from 0.012% to 12%–20%. This represents an enrichment increase by three orders of magnitude, surpassing our previous result by one order. Our method is particularly well-suited for isotope enrichment of elements with extremely low abundance.
Chinese Optics Letters
- Publication Date: Jul. 16, 2024
- Vol. 22, Issue 7, 070201 (2024)
Efficient cold atom source from a single-layer atom chip
Petr Skakunenko, Darya Bykova, Anton Afanasiev, Alexey Kalmykov, Roman Kirtaev, and Victor Balykin
We developed a new single-layer atom chip with an additional U-shaped current-carrying structure. The new U-shaped microwire creates optimized magnetic field distribution, which increases the trapping volume of a magneto-optical trap (MOT) near the chip. Our approach allows one to localize more atoms, while a setup remains relatively simple (single-layer approach) and consumes low current (up to 10 A). The total number of trapped 87Rb atoms in our setup is 5 × 107. We developed a new single-layer atom chip with an additional U-shaped current-carrying structure. The new U-shaped microwire creates optimized magnetic field distribution, which increases the trapping volume of a magneto-optical trap (MOT) near the chip. Our approach allows one to localize more atoms, while a setup remains relatively simple (single-layer approach) and consumes low current (up to 10 A). The total number of trapped 87Rb atoms in our setup is 5 × 107.
Chinese Optics Letters
- Publication Date: Jun. 20, 2024
- Vol. 22, Issue 6, 060201 (2024)
Reconstructing coherent dynamics of bound states induced by strong attosecond XUV pulses
Lijuan Jia, Mingqing Liu, Xinqiang Wang, Long Xu, Peiguang Yan, Wei-Chao Jiang, and Libin Fu
We propose a scheme that utilizes weak-field-induced quantum beats to investigate the electronic coherences of atoms driven by a strong attosecond extreme ultraviolet (XUV) pulse. The technique involves using a strong XUV pump pulse to excite and ionize atoms and a time-delayed weak short pulse to probe the photoelectron signal. Our theoretical analysis demonstrates that the information regarding the bound states, initiated by the strong pump pulse, can be precisely reconstructed from the weak-field-induced quantum beat spectrum. To examine this scheme, we apply it to the attosecond XUV laser-induced ionization of hydrogen atoms by solving a three-dimensional time-dependent Schrödinger equation. This work provides an essential reference for reconstructing the ultrafast dynamics of bound states induced by strong XUV attosecond pulses. We propose a scheme that utilizes weak-field-induced quantum beats to investigate the electronic coherences of atoms driven by a strong attosecond extreme ultraviolet (XUV) pulse. The technique involves using a strong XUV pump pulse to excite and ionize atoms and a time-delayed weak short pulse to probe the photoelectron signal. Our theoretical analysis demonstrates that the information regarding the bound states, initiated by the strong pump pulse, can be precisely reconstructed from the weak-field-induced quantum beat spectrum. To examine this scheme, we apply it to the attosecond XUV laser-induced ionization of hydrogen atoms by solving a three-dimensional time-dependent Schrödinger equation. This work provides an essential reference for reconstructing the ultrafast dynamics of bound states induced by strong XUV attosecond pulses.
Chinese Optics Letters
- Publication Date: Feb. 21, 2024
- Vol. 22, Issue 2, 020201 (2024)
Momentum filtering scheme of cooling atomic clouds for the Chinese Space Station
Hui Li, Biao Wu, Jiachen Yu, Xiaolong Yuan, Xiaoji Zhou, Bin Wang, Weibiao Chen, Wei Xiong, and Xuzong Chen
To obtain cold atom samples with temperatures lower than 100 pK in the cold atom physics rack experiment of the Chinese Space Station, we propose to use the momentum filtering method for deep cooling of atoms. This paper introduces the experimental results of the momentum filtering method verified by our ground testing system. In the experiment, we designed a specific experimental sequence of standing-wave light pulses to control the temperature, atomic number, and size of the atomic cloud. The results show that the momentum filter can effectively and conveniently reduce the temperature of the atomic cloud and the energy of Bose–Einstein condensation, and can be flexibly combined with other cooling methods to enhance the cooling effect. This work provides a method for the atomic cooling scheme of the ultra-cold atomic system on the ground and on the space station, and shows a way of deep cooling atoms. To obtain cold atom samples with temperatures lower than 100 pK in the cold atom physics rack experiment of the Chinese Space Station, we propose to use the momentum filtering method for deep cooling of atoms. This paper introduces the experimental results of the momentum filtering method verified by our ground testing system. In the experiment, we designed a specific experimental sequence of standing-wave light pulses to control the temperature, atomic number, and size of the atomic cloud. The results show that the momentum filter can effectively and conveniently reduce the temperature of the atomic cloud and the energy of Bose–Einstein condensation, and can be flexibly combined with other cooling methods to enhance the cooling effect. This work provides a method for the atomic cooling scheme of the ultra-cold atomic system on the ground and on the space station, and shows a way of deep cooling atoms.
Chinese Optics Letters
- Publication Date: Aug. 08, 2023
- Vol. 21, Issue 8, 080201 (2023)
Phase dependence of third-order harmonic generation in gases induced by two-color laser field|Editors' Pick
Congsen Meng, Pan Song, Zhihui Lyu, Xiaowei Wang, Dongwen Zhang, Zengxiu Zhao, and Jianmin Yuan
We experimentally demonstrate third-harmonic generation (THG) in gases ionized by a femtosecond laser pulse superimposed on its second-harmonic (SH). The mechanism of THG has been investigated, and it demonstrates that a third-order nonlinear process dominates at low pump intensity. Asymmetric third-harmonic (TH) spectra are observed at different time delays in two color fields, which are attributed to the process of the four-wave mixing (FWM) of the broad spectrum of pump pulses. A joint measurement on the terahertz (THz) and the TH is performed. It reveals that the optimized phase for the THG jumps from 0 to 0.5π as the pump intensity increases, which is different from the THz being a constant, and indicates that the THG arises from the nonlinearity of the third-order bound electrons to the tunnel-ionization current. We experimentally demonstrate third-harmonic generation (THG) in gases ionized by a femtosecond laser pulse superimposed on its second-harmonic (SH). The mechanism of THG has been investigated, and it demonstrates that a third-order nonlinear process dominates at low pump intensity. Asymmetric third-harmonic (TH) spectra are observed at different time delays in two color fields, which are attributed to the process of the four-wave mixing (FWM) of the broad spectrum of pump pulses. A joint measurement on the terahertz (THz) and the TH is performed. It reveals that the optimized phase for the THG jumps from 0 to 0.5π as the pump intensity increases, which is different from the THz being a constant, and indicates that the THG arises from the nonlinearity of the third-order bound electrons to the tunnel-ionization current.
Chinese Optics Letters
- Publication Date: May. 06, 2023
- Vol. 21, Issue 5, 050201 (2023)
Rydberg electromagnetically induced transparency in 40K ultracold Fermi gases
Guoqi Bian, Biao Shan, Lianghui Huang, and Jing Zhang
We report the measurement of the electromagnetically induced transparency (EIT) with Rydberg states in ultracold K40 Fermi gases, which is obtained through a two-photon process with the ladder scheme. Rydberg–EIT lines are obtained by measuring the atomic losses instead of the transmitted probe beam. Based on the laser frequency stabilization locking to the superstable cavity, we study the Rydberg–EIT line shapes for the 37s and 35d states. We experimentally demonstrate the significant change in the Rydberg–EIT spectrum by changing the principal quantum number of the Rydberg state (n=37/52 and l=0). Moreover, the transparency peak position shift is observed, which may be induced by the interaction of the Rydberg atoms. This work provides a platform to explore many interesting behaviors involving Rydberg states in ultracold Fermi gases. We report the measurement of the electromagnetically induced transparency (EIT) with Rydberg states in ultracold K40 Fermi gases, which is obtained through a two-photon process with the ladder scheme. Rydberg–EIT lines are obtained by measuring the atomic losses instead of the transmitted probe beam. Based on the laser frequency stabilization locking to the superstable cavity, we study the Rydberg–EIT line shapes for the 37s and 35d states. We experimentally demonstrate the significant change in the Rydberg–EIT spectrum by changing the principal quantum number of the Rydberg state (n=37/52 and l=0). Moreover, the transparency peak position shift is observed, which may be induced by the interaction of the Rydberg atoms. This work provides a platform to explore many interesting behaviors involving Rydberg states in ultracold Fermi gases.
Chinese Optics Letters
- Publication Date: Aug. 30, 2023
- Vol. 21, Issue 10, 100201 (2023)
Automatic, long-term frequency-stabilized lasers with sub-hertz linewidth and 10−16 frequency instability
Chengzhi Yan, Haosen Shi, Yuan Yao, Hongfu Yu, Yanyi Jiang, and Longsheng Ma
We report two ultra-stable laser systems automatically frequency-stabilized to two high-finesse optical cavities. By employing analog-digital hybrid proportional integral derivative (PID) controllers, we keep the merits of wide servo bandwidth and servo accuracy by using analog circuits for the PID controller, and, at the same time, we realize automatic laser frequency locking by introducing digital logic into the PID controller. The lasers can be automatically frequency-stabilized to their reference cavities, and it can be relocked in 0.3 s when interruption happens, i.e., blocking and unblocking the laser light. These automatic frequency-stabilized lasers are measured to have a frequency instability of 6×10-16 at 1 s averaging time and a most probable linewidth of 0.3 Hz. The laser systems were tested for continuous operation over 11 days. Such ultra-stable laser systems in long-term robust operation will be beneficial to the applications of optical atomic clocks and precision measurement based on frequency-stabilized lasers. We report two ultra-stable laser systems automatically frequency-stabilized to two high-finesse optical cavities. By employing analog-digital hybrid proportional integral derivative (PID) controllers, we keep the merits of wide servo bandwidth and servo accuracy by using analog circuits for the PID controller, and, at the same time, we realize automatic laser frequency locking by introducing digital logic into the PID controller. The lasers can be automatically frequency-stabilized to their reference cavities, and it can be relocked in 0.3 s when interruption happens, i.e., blocking and unblocking the laser light. These automatic frequency-stabilized lasers are measured to have a frequency instability of 6×10-16 at 1 s averaging time and a most probable linewidth of 0.3 Hz. The laser systems were tested for continuous operation over 11 days. Such ultra-stable laser systems in long-term robust operation will be beneficial to the applications of optical atomic clocks and precision measurement based on frequency-stabilized lasers.
Chinese Optics Letters
- Publication Date: May. 26, 2022
- Vol. 20, Issue 7, 070201 (2022)
Dark state atoms trapping in a magic-wavelength optical lattice near the nanofiber surface
Dianqiang Su, Xiateng Qin, Yuan Jiang, Kaidi Jin, Zhonghua Ji, Yanting Zhao, Liantuan Xiao, and Suotang Jia
We report the experimental realization of dark state atoms trapping in a nanofiber optical lattice. By applying the magic-wavelength trapping potentials of cesium atoms, the AC Stark shifts are strongly suppressed. The dark magneto-optical trap efficiently transfers the cold atoms from bright (6S1/2, F = 4) into dark state (6S1/2, F = 3) for hyperfine energy levels of cesium atoms. The observed transfer efficiency is as high as 98% via saturation measurement. The trapping lifetime of dark state atoms trapped by a nanofiber optical lattice is also investigated, which is the key element for realizing optical storage. This work contributes to the manipulation of atomic electric dipole spin waves and quantum information storage for fiber networks. We report the experimental realization of dark state atoms trapping in a nanofiber optical lattice. By applying the magic-wavelength trapping potentials of cesium atoms, the AC Stark shifts are strongly suppressed. The dark magneto-optical trap efficiently transfers the cold atoms from bright (6S1/2, F = 4) into dark state (6S1/2, F = 3) for hyperfine energy levels of cesium atoms. The observed transfer efficiency is as high as 98% via saturation measurement. The trapping lifetime of dark state atoms trapped by a nanofiber optical lattice is also investigated, which is the key element for realizing optical storage. This work contributes to the manipulation of atomic electric dipole spin waves and quantum information storage for fiber networks.
Chinese Optics Letters
- Publication Date: Nov. 19, 2021
- Vol. 20, Issue 2, 020201 (2022)
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