arXiv subjects

Jiandong Bai

Publications and source records attributed to Jiandong Bai.

10 recordsLinked to original sources

arXiv2023

Autler-Townes splitting in the trap-loss fluorescence spectroscopy due to single-step direct Rydberg excitation of cesium cold atomic ensemble

We experimentally investigate trap-loss spectra of the cesium 6S1/2(F=4)-71P3/2 Rydberg state by combining the cesium atomic magneto-optical trap with the narrow-linewidth, continuously-tunable 318.6 nm ultraviolet laser. That is, the atoms in the magneto-optical trap are excited to the Rydberg state due to the ultraviolet laser single-step Rydberg excitation, which leads to the reduction of atomic fluorescence. Based on the trap-loss spectroscopy technology, the Autler-Townes splitting due to strong cooling laser is observed, and the parameter dependence of the AT splitting interval of trap-loss spectroscopy is investigated. Furthermore, the effective temperature of cold atoms is measured by means of simplified time-of-flight fluorescence imaging. In addition, closed-loop positive feedback power stabilization of 318.6 nm ultraviolet laser is carried out. This lays the foundation for further experimental research related to Rydberg atoms using ultraviolet lasers, which is of great significance for the development of quantum computing and quantum information fields.

physics.atom-ph↗

arXiv2020

Measuring the hyperfine splittings and deriving the hyperfine-interaction constants of Cesium 7D 5/2 excited state

The measurement of Cesium (Cs) 7D5/2 excited state's hyperfine splitting intervals and hyperfine-interaction constants has been experimentally investigated based on ladder-type (852 nm + 698 nm) three-level Cs system (6S1/2 - 6P3/2 - 7D5/2) with room-temperature Cs atomic vapor cell. By scanning the 698-nm coupling laser's frequency, the Doppler-free high-resolution electromagnetically-induced transparency (EIT) assisted double-resonance optical pumping (DROP) spectra have been demonstrated via transmission enhancement of the locked 852-nm probe laser. The EIT-assisted DROP spectra are employed to study the hyperfine splitting intervals for the Cs 7D5/2 excited state with a room-temperature cesium atomic vapor cell, and the radio-frequency modulation sideband of a waveguide-type electro-optic phase modulator(EOPM) is introduced for frequency calibration to improve the accuracy of frequency interval measurement. The existence of EIT makes the DROP spectral linewidth much narrower, and it is very helpful to improve the spectroscopic resolution significantly. Benefiting from the higher signal-to-noise ratio (SNR) and much better resolution of the EIT-assisted DROP spectra, the hyperfine splitting intervals between the hyperfine folds of (F" = 6), (F" = 5), and (F" = 4) of cesium 7D5/2 state (HFS6"-5" = -10.60(0.17) MHz and HFS5"-4" = -8.54(0.15) MHz) have been measured, and therefore the magnetic-dipole hyperfine-interaction constant (A = -1.70(0.03) MHz) and the electric-quadrupole hyperfine-interaction constant (B = -0.77(0.58) MHz) have been derived for the Cs 7D5/2 state. These constants have important reference value for the improvement of precise measurement and determination of basic physical constants.

physics.atom-ph↗

arXiv2020

Rydberg level shift due to the electric field generated by Rydberg atom collision induced ionization in cesium atomic ensemble

We experimentally studied the Rydberg level shift caused by the electric field, which is generated by Rydberg atom collision induced ionization in a cesium atomic ensemble. The density of charged particles caused by collisions between Rydberg atoms is changed by controlling the ground-state atomic density and optical excitation process. We measured the Rydberg level shift using Rydberg electromagnetically-induced-transparency (EIT) spectroscopy, and interpreted the physical origin using a semi-classical model. The experimental results are in good agreement with the numerical simulation. These energy shifts are important for the self-calibrated sensing of microwave field by the employing of Rydberg EIT. Moreover, in contrast to the resonant excitation case, narrow-linewidth spectroscopy with high signal-to-noise ratio would be useful for high-precision measurements.

physics.atom-ph↗

arXiv2020

Towards implementation of a magic optical-dipole trap for confining ground-state and Rydberg-state cesium cold atoms

Long ground-Rydberg coherence lifetime is interesting for implementing high-fidelity quantum logic gates, many-body physics, and other quantum information protocols. However, the potential formed by a conventional far-off-resonance red-detuned optical-dipole trap (ODT) is usually repulsive for Rydberg atoms, which will result in fast atom loss and low repetition rate of the experimental sequence. These issues can be addressed by a magic ODT. We performed the calculation of ODT's magic detuning for confinement of cesium ground state and Rydberg state with the same potential well. We used a sum-over-states method to calculate the dynamic polarizabilities of $6S_{1/2}$ ground state and highly-excited ($nS_{1/2}$ and $nP_{3/2}$) Rydberg state of cesium atoms, and identify corresponding magic detuning for optical wavelengths in the range of $850 - 2000$ nm. We estimated the trapping lifetime of cesium Rydberg atoms confined in the magic ODT by including different dissipative mechanisms. Furthermore, we have experimentally realized an 1879.43-nm single-frequency laser system with a watt-level output power for setting up the magic ODT for $6S_{1/2}$ ground-state and $84P_{3/2}$ Rydberg-state cesium cold atoms.

physics.atom-ph↗

arXiv2019

Single-Photon Rydberg Excitation and Trap-Loss Spectroscopy of Cold Cesium Atoms in a Magneto-Optical Trap by Using of a 319-nm Ultra-Violet Laser System

We demonstrate the single-photon Rydberg excitation of cesium atoms in a magneto-optical trap (MOT). We excite atoms directly from ${{6S}_{1/2}}$ ground state to ${{nP}_{3/2}}(n=70-100)$ Rydberg state with a narrow-linewidth 319 nm ultra-violet laser. The detection of Rydberg states is performed by monitoring the reduction of fluorescence signal of the MOT as partial population on ${{6S}_{1/2}} (F = 4)$ ground state are transferred to Rydberg state. We clearly observe Autler-Townes doublet in the trap-loss spectra due to the cooling lights. Utilizing the large electric polarizibility of Rydberg atoms, we observe Stark splitting in the Autler-Townes doublet induced by background DC electric fields. We investigate the dependence of Stark shift on electric fields by theoretical analysis, and then infer the DC electric field from the measured Stark splitting. We find that there is a 44.8(4) mV/cm DC electric field in the vicinity of the cold ensemble. It indicates that high-lying Rydberg atoms can be used as sensors for DC electric fields.

physics.atom-ph↗

arXiv2018

Autler-Townes doublet in single-photon Rydberg spectra of Cesium atomic vapor with a 319 nm UV laser

We demonstrate the single-photon excitation spectra of cesium Rydberg atoms by means of a Doppler-free purely all-optical detection with a room-temperature vapor cell and a 319 nm ultra-violet (UV) laser. We excite atoms directly from 6S1/2 ground state to 71P3/2 Rydberg state with a narrow-linewidth 319 nm UV laser. The detection of Rydberg states is performed by monitoring the absorption of an 852 nm probe beam in a V-type three-level system. With a strong coupling light, we observe the Autler-Townes doublet and investigate experimentally the dependence of the separation and linewidth on the coupling intensity, which is consistent with the prediction based on the dressed state theory. We further investigate the Rydberg spectra with an external magnetic field. The existence of non-degenerate Zeeman sub-levels results in the broadening and shift of the spectra. It has potential application in sensing magnetic field.

physics.atom-ph↗

arXiv2017

Single-photon cesium Rydberg excitation spectroscopy using 318.6-nm UV laser and room-temperature vapor cell

We demonstrate a single-photon Rydberg excitation spectroscopy of cesium (Cs) atoms in a room-temperature vapor cell. Cs atoms are excited directly from 6S1/2 ground state to nP3/2 (n = 70 - 100) Rydberg states with a 318.6 nm ultraviolet (UV) laser,and Rydberg excitation spectra are obtained by transmission enhancement of a probe beam resonant to Cs 6S1/2, F = 4 - 6P3/2, F' = 5 transition as partial population on F = 4 ground state are transferred to Rydberg state .Analysis reveals that the observed spectra are velocity-selective spectroscopy of Rydberg state, from which the amplitude and linewidth influenced by lasers'Rabi frequency have been investigated. Fitting to energies of Cs nP3/2 (n = 70 -100) states, the determined quantum defect is 3.56671(42). The demodulated spectra can also be employed as frequency references to stabilize the UV laser frequency to specific Cs Rydberg transition.

physics.atom-ph↗

arXiv2016

Development and characterization of a 2.2 W narrow-linewidth 318.6 nm ultraviolet laser

We demonstrate a high-power narrow-linewidth ultraviolet (UV) laser system at 318.6 nm for direct 6S1/2-nP (n = 70 to 100) Rydberg excitation of cesium atoms. Based on commercial fiber lasers and efficient nonlinear frequency conversion technology, 2.26 W of tunable UV laser power is obtained from cavity-enhanced second harmonic generation following sum-frequency generation of two infrared lasers at 1560.5 nm and 1076.9 nm to 637.2 nm. The maximum doubling efficiency is 57.3%. The typical UV laser power root-mean-square fluctuation is less than 0.87% over 30 minutes, and the continuously tunable range of the UV laser frequency is more than 6 GHz. Its beam quality factors M2 X and M2 Y are 1.16 and 1.48, respectively. This high-performance UV laser has significant potential use in quantum optics and cold atom physics.

physics.optics↗

arXiv2016

Electronic sideband locking of 318.6nm UV laser to an ultrastable optical cavity with a wide continuously tunable range

We have demonstrated a frequency-stabilized tunable 318.6 nm ultraviolet (UV) laser system for the single-photon 6S1/2 - nP (n = 70 ~ 100) Rydberg excitation of cesium atoms. The 637.2 nm laser produced by single-pass sum frequency generation from two infrared fiber lasers is offset locked to a high-finesse ultra-low expansion (ULE) optical cavity placed in ultra-high vacuum using the electronic sideband locking technique. The generated 318.6 nm UV laser via cavity-enhanced second-harmonic generation can be continuously tuned over 4 GHz by indirectly changing modulation frequency on the electro-optic phase modulator while the whole laser system remains locked. We analyze the tuning range mainly depends on the modulator bandwidth and the tunable range of the seed laser. The locking scheme offers a method to compensate the frequency difference between the reference frequency and the goal frequency to a desired excited state, and has huge potential in precision spectroscopic experiments of cold atoms.

physics.atom-ph↗

arXiv2016

Realization and characterization of single-frequency tunable 637.2 nm high-power laser

We report the generation of narrow-linewidth 637.2 nm laser by single-pass sum-frequency generation (SFG) of two infrared lasers at 1560.5 nm and 1076.9 nm in PPMgO:LN crystal. Over 8.75 W of single-frequency continuously tunable 637.2 nm laser is realized, and corresponding conversion efficiency is 38%. We study the behavior of crystals with different poling periods. The detailed experiments show that the output red lasers have very good power stability and beam quality. This high-performance 637.2 nm laser is significant for the realization of high power ultra-violet (UV) 318.6 nm laser via cavity-enhanced frequency doubling. Narrow-linewidth 318.6 nm laser is important for Rydberg excitation of cesium atoms via single-photon transition.

physics.optics↗