This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium(Sr)atomic space optical clock.The system’s core components,physical unit,optical unit,and electric...This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium(Sr)atomic space optical clock.The system’s core components,physical unit,optical unit,and electrical unit,have a total volume of 306 L and a total mass of 163.8 kg.These compact and robust units can overcome mechanical vibrations and temperature fluctuations during space launch.The laser sources of the optical unit are composed of diode lasers,and the injection locking of slave lasers is automatically performed by a program.In the experiment,a blue magneto-optical trap of cold atoms was achieved,with the atom numbers estimated to be approximately(1.50±0.13)×10^(6) for 87Sr and(8.00±0.56)×10^(6) for 88Sr.This work establishes a foundation for atomic confinement and high-precision interrogation in space-based optical clocks and expands the frontiers of cold atom physics in microgravity.展开更多
Isotropic laser cooling(ILC)is widely recognized for its distinct advantages and demonstrates significant potential in quantum precision measurements and quantum sensing technologies.The morphology and density distrib...Isotropic laser cooling(ILC)is widely recognized for its distinct advantages and demonstrates significant potential in quantum precision measurements and quantum sensing technologies.The morphology and density distribution of the cold atomic cloud generated by ILC are strongly influenced by the distribution of cooling light and the structural geometry of the cavity,making precise characterization and optimization of cold atom distribution essential for practical applications.In this paper,we present an innovative flat diffuse cavity design with the dimensions approximating a quasi-two-dimensional configuration,which generates a sheet-like isotropic laser field inside the cavity through diffuse reflections.We thoroughly characterized the system’s performance under different optical parameter settings.A two-dimensional(2D)movable detection system was employed to detect the quasi-two-dimensional distribution of cold atoms.These results demonstrate the ability of ILC to produce diverse morphological and density distributions of cold atoms,which we anticipate will be suitable for quantum sensing.展开更多
Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and ex...Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and exciting applications. In this paper, the radical 138Ba19F, as a promising candidate for laser cooling and magneto-optical trapping, is discussed in detail.The highly diagonal Franck-Condon factors between theX2∑＋1/2and A2∏1/2states are first confirmed with three different methods. Afterwards, with the effective Hamiltonian approach and irreducible tensor theory, the hypertine structure of theX2∑＋1/2state is calculated accurately. A scheme for laser cooling is given clearly. Besides, the Zeeman effects of the upper （ A2∏1/2）andlower（X2∑＋1/2）levels are also studied, and their respective g factors are obtained under a weak magnetic field. Its large g factor of the upper stateA2∏1/2is advantageous for magneto-optical trapping. Finally, by studying Stark effect of BaFin theX2∑＋1/2, we investigate the dependence of the internal effective electric field on the applied electric field. It is suggested that such a laser-cooled BaF is also a promising candidate for precision measurement of electron electric dipole moment.展开更多
We investigate whether A1C1 and A1Br are promising candidates for laser cooling. We report new ab initio calculations on the ground state X1E＋ and two low-lying states （A1H and a3H） of A1C1 and A1Br. The calculated...We investigate whether A1C1 and A1Br are promising candidates for laser cooling. We report new ab initio calculations on the ground state X1E＋ and two low-lying states （A1H and a3H） of A1C1 and A1Br. The calculated spectroscopic constants show good agreement with available theoretical and experimental results. We also obtain the permanent dipole moments （PDMs） curve at multi-reference configuration interaction （MRCI） level of theory. The transition properties of A1H and a3H states are predicted, including the transition dipole moments （TDMs）, Franck-Condon factors （FCFs）, radiative times and radiative width. The calculated radiative lifetimes are of the order of a nanosecond, implying that they are sufficiently short for rapid laser cooling. Both A1C1 and A1Br have highly diagonally distributed FCFs which are crucial requirement for molecular laser cooling. The results demonstrate the feasibility of laser cooling A1C1 and A1Br, and we propose laser cooling schemes for A1C1 and A1Br.展开更多
We report on the efficient gray molasses cooling of sodium atoms using the D2 optical transition at 589.1 nm.Thanks to the hyperfine split about 6Γ between |F’ = 2> and |F’ = 3> in the excited state 32 P3/2, ...We report on the efficient gray molasses cooling of sodium atoms using the D2 optical transition at 589.1 nm.Thanks to the hyperfine split about 6Γ between |F’ = 2> and |F’ = 3> in the excited state 32 P3/2, this atomic transition is effective for the gray molasses cooling mechanism. Using this cooling technique, the atomic sample in F = 2 ground manifold is cooled from 700 μK to 56 μK in 3.5 ms. We observe that the loading efficiency into magnetic trap is increased due to the lower temperature and high phase space density of atomic cloud after gray molasses. This technique offers a promising route for the fast cooling of the sodium atoms in the F = 2 state.展开更多
The Al^＋ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic...The Al^＋ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of AI＋ ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al^＋ traps are utilized. The first trap is used to trap a large number of Al^＋ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al^＋ ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167nm laser. The expected clock laser stability can reach 9.0 × 10^-17/√τ. For the second trap, in addition to 167nm laser Doppler cooling, a second stage pulsed 234nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about 1 × 10^-18. The proposed Al^＋ ion optical clock has the potential to become the most accurate and stable optical clock.展开更多
The enhanced laser cooling performance of rare-earth-ions-doped glasses containing small particles is predicted. This is achieved by the enhancement of local field around rare earth ions, owing to the surface plasmon ...The enhanced laser cooling performance of rare-earth-ions-doped glasses containing small particles is predicted. This is achieved by the enhancement of local field around rare earth ions, owing to the surface plasmon resonance of small metallic particles. The role of energy transfer between ions and the particle is theoretical discussed. Depending on the particle size and the ion emission quantum efficiency, the enhancement of the absorption and the fluorescence is predicted. Moreover, taking Yb^3＋-doped ZBLAN as example, the cooling power and heat-light converting efficiency are calculated. It is finally concluded that the absorption and the fluorescence are greatly enhanced in these composite materials, the cooling power is increased compared to the bulk material.展开更多
The feasibility of laser cooling a CH molecule is investigated theoretically by employing the ab initio method. The potential energy curves for the five ∧-S states and eight Ω states of CH are determined by the mult...The feasibility of laser cooling a CH molecule is investigated theoretically by employing the ab initio method. The potential energy curves for the five ∧-S states and eight Ω states of CH are determined by the multi-reference configuration interaction with the Davidson corrections（MRCI＋Q） level of theory. The results agree well with the available experimental data and other theoretical values. Also, the permanent dipole moments and transition dipole moments of the CH molecule are calculated at the multi-reference configuration interaction（MRCI） level. We find highly diagonally distributed FranckCondon factors（f00 = 0.9950 and 0.9998） and branching ratios（R00 = 0.983 and 0.993） for the A^2△→ X2Π and C^2∑^＋→X^2Π transitions. Moreover, the values of suitable radiative lifetime τ of the A2 A and C^2∑^＋ states are evaluated to be9.64×10^-7 s and 2.02×10^-7 s, respectively, for rapid laser cooling. A scheme for laser cooling the CH molecule is designed. In the proposed cooling scheme, three wavelengths for A^2△→X^2Π and C^2∑^＋→X^2Π transitions are used, and the main pump lasers are λ00=430.86 nm and 313.45 nm, respectively. The feasibility of laser cooling the CH molecules is demonstrated for each of these schemes, and this study offers a theoretical basis for experimental research into preparation of cold CH molecules.展开更多
We propose a scheme to prepare the steady-state entanglement for two atoms, which are held in separate cavities that are coupled through a short optical fiber or optical resonator. The entangled steady-state with a hi...We propose a scheme to prepare the steady-state entanglement for two atoms, which are held in separate cavities that are coupled through a short optical fiber or optical resonator. The entangled steady-state with a high fidelity can be achieved even with a low cooperativity parameter, by making use of the driving laser fields. Such a cooling mechanism is based on a resonant laser pump of the unwanted ground states to the excited states, which finally decay to the desired steady-state.展开更多
We demonstrate an integrating sphere to cool~(87)Rb atoms and measure the recoil-induced resonance and electromagnetically induced absorption spectrum.We measure the relationship between their linewidth and light shif...We demonstrate an integrating sphere to cool~(87)Rb atoms and measure the recoil-induced resonance and electromagnetically induced absorption spectrum.We measure the relationship between their linewidth and light shift with variation of the detuning and power of the cooling laser and study the performance of the diffuse laser cooling mechanism by the absorption linewidth radio?ν_E/?ν_R and light shift|?_R-?_E|using nonlinear spectroscopy.Specifically,when?ν_E/?ν_R reaches a value of 1.57,the temperature and number of cold atoms achieve the optimal cooling effect.This characterization of absorption linewidth and light shift will provide a method to estimate whether diffuse light cooling achieves the best cooling effect,contributing to the future development of isotropic laser cooling for application in quantum sensing.展开更多
We extend the idea of laser cooling with adiabatic passage to multi-level type-Ⅱ transitions.We find the cooling force can be significantly enhanced when a proper magnetic field is applied.That is because the magneti...We extend the idea of laser cooling with adiabatic passage to multi-level type-Ⅱ transitions.We find the cooling force can be significantly enhanced when a proper magnetic field is applied.That is because the magnetic field decomposes the multi-level system into several two-level sub-systems,hence the stimulated absorption and stimulated emission can occur in order,allowing for the multiple photon momentum transfer.We show that this scheme also works on the laser-coolable molecules with a better cooling effect compared to the conventional Doppler cooling.A reduced dependence on spontaneous emission based on our scheme is observed as well.Our results suggest this scheme is very feasible for laser cooling of polar molecules.展开更多
The recent progress on Raman scattering in GaN single crystals and GaN/A1N heterostructures is re- viewed. Anti-Stokes Raman scattering is used to determine electron-phonon scattering time and decay time constant for ...The recent progress on Raman scattering in GaN single crystals and GaN/A1N heterostructures is re- viewed. Anti-Stokes Raman scattering is used to determine electron-phonon scattering time and decay time constant for longitudinal-opticat phonons. In a typical high electron mobility transistor based on GaN/A1N heterostructures, strong resonances are reached for the first-order and second-order Raman scattering processes. Therefore, both Stokes and anti-Stokes Raman intensities are dramatically enhanced. The feasibility for laser cooling of a nitride structure is studied. A further optimization will enable us to reach the threshold for laser cooling. Raman scattering have potential applications in up-conversion lasers and laser cooling of nitride ultrafast electronic and optoelectronic devices.展开更多
We propose a new method to cool the yb^3＋-doped ZBLANP glass in a standing-wave cavity. There are two advantages of this cavity-enhanced technique： the pumping power is greatly enhanced and the absorption of the coo...We propose a new method to cool the yb^3＋-doped ZBLANP glass in a standing-wave cavity. There are two advantages of this cavity-enhanced technique： the pumping power is greatly enhanced and the absorption of the cooling material is greatly increased. We introduce the basic principle of the cavity-enhanced laser cooling and discuss the cooling effect of a solid-state material in a cavity. From the theoretical study, it is found that the laser cooling effect is strongly dependent on the reflectivity of the cavity mirrors, the length of the solid material, the surface scattering of the material, and so on. Some optimal parameters for efficient laser cooling are obtained.展开更多
We investigate the process of pulsed laser cooling using a self-constructed molecular dynamics simulation(MDSimulation)program.We simulate the Doppler cooling process and pulsed laser Doppler cooling process of a sing...We investigate the process of pulsed laser cooling using a self-constructed molecular dynamics simulation(MDSimulation)program.We simulate the Doppler cooling process and pulsed laser Doppler cooling process of a single^(40)Ca^(+)ion,and the comparison with the experimental results shows that this self-constructed MD-Simulation program works well in the weak laser intensity situation.Furthermore,we analyze the pulsed laser Doppler cooling process of a single^(27)Al^(+)ion.This program can be used to analyze the molecular dynamic process of various situations of Doppler cooling in an ion trap,which could give predictions and experimental guidance.展开更多
We demonstrate a simple and fast way to produce 87Rb Bose–Einstein condensates. A digital optical phase lock loop(OPLL) board is introduced to lock and adjust the frequency of the trap laser, which simplifies the opt...We demonstrate a simple and fast way to produce 87Rb Bose–Einstein condensates. A digital optical phase lock loop(OPLL) board is introduced to lock and adjust the frequency of the trap laser, which simplifies the optical design and improves the experimental efficiency. We collect atoms in a magneto-optical trap, then compress the cloud and cut off hot atoms by rf knife in a magnetic quadrupole trap. The atom clouds are then transferred into a spatially mode-matched optical dipole trap by lowering the quadrupole field gradient. Our system reliably produces a condensate with 2 × 106 atoms every7.5 s. The compact optical design and rapid preparation speed of our system will open the gate for mobile quantum sensing.展开更多
Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. C...Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. Considering Rb atoms as an example, it finds that the numerical results are relevant to the recent experimental laser cooling investigations.展开更多
Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one- dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes ...Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one- dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes like 172yb, Jv3yb, and J74yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are studied, and the optimal parameters for the isotope separation are also investigated. Furthermore, the isotope separation efficiency and purity are estimated. Finally a new scheme for the efficient isotope separation is proposed. These findings will give a guideline for simply obtaining pure isotopes of various elements.展开更多
The use of a broadband, frequency shaped femtosecond laser on translationally cold cesium molecules has recently demonstrated to be a very efficient method of cooling also the vibrational degree of freedom. A sample o...The use of a broadband, frequency shaped femtosecond laser on translationally cold cesium molecules has recently demonstrated to be a very efficient method of cooling also the vibrational degree of freedom. A sample of cold molecules, initially distributed over several vibrational levels, has thus been transfered into a single selected vibrational level of the singlet X^1∑g ground electronic state. Our method is based on repeated optical pumping by laser light with a spectrum broad enough to excite all populated vibrational levels but limited in its frequency bandwidth with a spatial light modulator. In such a way we are able to eliminate transitions from the selected level, in which molecules accumulate. In this paper we briefly report the main experimental results and then address, in a detailed way by computer simulations, the perspectives for a ＂complete＂ cooling of the molecules, including also the rotational degree of freedom. Since the pumping process strongly depends on the relative shape of the ground and excited potential curves, ro-vibrational cooling through different excited states is theoretically compared.展开更多
Doppler cooling of^(88)Sr atoms is studied in the presence of off-resonant red-detuned fluctuating laser fields.Using a semi-classical approach,we show that the relevant physical quantities in the cooling process,such...Doppler cooling of^(88)Sr atoms is studied in the presence of off-resonant red-detuned fluctuating laser fields.Using a semi-classical approach,we show that the relevant physical quantities in the cooling process,such as optical forces,the damping coefficient,Doppler temperature,and atom number in the trap,are strongly affected by the laser amplitude and phase fluctuations.We find that the Doppler cooling limit is higher than the predicted Doppler theory for non-fluctuating lasers.This implies an additional heating mechanism exists due to the laser fluctuations.Furthermore,our numerical analysis shows that the effect of laser power stability on reducing the number of trapped atoms in a magneto-optical trap is more substantial than the effect of laser linewidth.展开更多
We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possibl...We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possible to cool a resonator to its ground state in the strong cavity-atom coupling regime.Moreover,with the assistance of one additional energy level,our scheme takes a larger cooling rate to realize the ground state cooling.In addition,this scheme is a feasible candidate for experimental applications.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB35010202)the National Natural Science Foundation of China(Grants No.62275268)。
文摘This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium(Sr)atomic space optical clock.The system’s core components,physical unit,optical unit,and electrical unit,have a total volume of 306 L and a total mass of 163.8 kg.These compact and robust units can overcome mechanical vibrations and temperature fluctuations during space launch.The laser sources of the optical unit are composed of diode lasers,and the injection locking of slave lasers is automatically performed by a program.In the experiment,a blue magneto-optical trap of cold atoms was achieved,with the atom numbers estimated to be approximately(1.50±0.13)×10^(6) for 87Sr and(8.00±0.56)×10^(6) for 88Sr.This work establishes a foundation for atomic confinement and high-precision interrogation in space-based optical clocks and expands the frontiers of cold atom physics in microgravity.
基金supported by the National Natural Science Foun-dation of China(Grant No.92165107)the China Postdoctoral Science Foundation(Grant No.2022M723270)the National Defense Basic Scientific Research Pogram of China。
文摘Isotropic laser cooling(ILC)is widely recognized for its distinct advantages and demonstrates significant potential in quantum precision measurements and quantum sensing technologies.The morphology and density distribution of the cold atomic cloud generated by ILC are strongly influenced by the distribution of cooling light and the structural geometry of the cavity,making precise characterization and optimization of cold atom distribution essential for practical applications.In this paper,we present an innovative flat diffuse cavity design with the dimensions approximating a quasi-two-dimensional configuration,which generates a sheet-like isotropic laser field inside the cavity through diffuse reflections.We thoroughly characterized the system’s performance under different optical parameter settings.A two-dimensional(2D)movable detection system was employed to detect the quasi-two-dimensional distribution of cold atoms.These results demonstrate the ability of ILC to produce diverse morphological and density distributions of cold atoms,which we anticipate will be suitable for quantum sensing.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91536218,11374100,10904037,10974055,11034002,and 11274114)the National Key Basic Research and Development Program of China(Grant No.2011CB921602)the Natural Science Foundation of Shanghai Municipality,China(Grant No.13ZR1412800)
文摘Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and exciting applications. In this paper, the radical 138Ba19F, as a promising candidate for laser cooling and magneto-optical trapping, is discussed in detail.The highly diagonal Franck-Condon factors between theX2∑＋1/2and A2∏1/2states are first confirmed with three different methods. Afterwards, with the effective Hamiltonian approach and irreducible tensor theory, the hypertine structure of theX2∑＋1/2state is calculated accurately. A scheme for laser cooling is given clearly. Besides, the Zeeman effects of the upper （ A2∏1/2）andlower（X2∑＋1/2）levels are also studied, and their respective g factors are obtained under a weak magnetic field. Its large g factor of the upper stateA2∏1/2is advantageous for magneto-optical trapping. Finally, by studying Stark effect of BaFin theX2∑＋1/2, we investigate the dependence of the internal effective electric field on the applied electric field. It is suggested that such a laser-cooled BaF is also a promising candidate for precision measurement of electron electric dipole moment.
文摘We investigate whether A1C1 and A1Br are promising candidates for laser cooling. We report new ab initio calculations on the ground state X1E＋ and two low-lying states （A1H and a3H） of A1C1 and A1Br. The calculated spectroscopic constants show good agreement with available theoretical and experimental results. We also obtain the permanent dipole moments （PDMs） curve at multi-reference configuration interaction （MRCI） level of theory. The transition properties of A1H and a3H states are predicted, including the transition dipole moments （TDMs）, Franck-Condon factors （FCFs）, radiative times and radiative width. The calculated radiative lifetimes are of the order of a nanosecond, implying that they are sufficiently short for rapid laser cooling. Both A1C1 and A1Br have highly diagonally distributed FCFs which are crucial requirement for molecular laser cooling. The results demonstrate the feasibility of laser cooling A1C1 and A1Br, and we propose laser cooling schemes for A1C1 and A1Br.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0301602the National Natural Science Foundation of China under Grant Nos 11474188 and 11704234+1 种基金the National Key Research and Development Program of China under Grant No 2018YFA0307601the Fund for Shanxi ‘1331 Project’ Key Subjects Construction,and the Program of Youth Sanjin Scholar
文摘We report on the efficient gray molasses cooling of sodium atoms using the D2 optical transition at 589.1 nm.Thanks to the hyperfine split about 6Γ between |F’ = 2> and |F’ = 3> in the excited state 32 P3/2, this atomic transition is effective for the gray molasses cooling mechanism. Using this cooling technique, the atomic sample in F = 2 ground manifold is cooled from 700 μK to 56 μK in 3.5 ms. We observe that the loading efficiency into magnetic trap is increased due to the lower temperature and high phase space density of atomic cloud after gray molasses. This technique offers a promising route for the fast cooling of the sodium atoms in the F = 2 state.
基金Supported by the National Basic Research Program of China under Grant No 2012CB821300the National Natural Science Foundation of China under Grant Nos 91336213,11304109,91536116 and 11174095the Program for New Century Excellent Talents by the Ministry of Education under Grant No NCET-11-0176
文摘The Al^＋ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of AI＋ ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al^＋ traps are utilized. The first trap is used to trap a large number of Al^＋ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al^＋ ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167nm laser. The expected clock laser stability can reach 9.0 × 10^-17/√τ. For the second trap, in addition to 167nm laser Doppler cooling, a second stage pulsed 234nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about 1 × 10^-18. The proposed Al^＋ ion optical clock has the potential to become the most accurate and stable optical clock.
基金supported by the National Natural Science Foundation of China under Grant Nos.10434060 and 10674047the Doctor Foundation of the Ministry of Education under Grant No.20040269010Shanghai Priority Academic Discipline,and the 211 Foundation of the Ministry of Education Doctor Program Scholarship Fund of ECNU 2007
文摘The enhanced laser cooling performance of rare-earth-ions-doped glasses containing small particles is predicted. This is achieved by the enhancement of local field around rare earth ions, owing to the surface plasmon resonance of small metallic particles. The role of energy transfer between ions and the particle is theoretical discussed. Depending on the particle size and the ion emission quantum efficiency, the enhancement of the absorption and the fluorescence is predicted. Moreover, taking Yb^3＋-doped ZBLAN as example, the cooling power and heat-light converting efficiency are calculated. It is finally concluded that the absorption and the fluorescence are greatly enhanced in these composite materials, the cooling power is increased compared to the bulk material.
基金Project supported by the National Natural Science Foundation of China(Grant No.61705182)
文摘The feasibility of laser cooling a CH molecule is investigated theoretically by employing the ab initio method. The potential energy curves for the five ∧-S states and eight Ω states of CH are determined by the multi-reference configuration interaction with the Davidson corrections（MRCI＋Q） level of theory. The results agree well with the available experimental data and other theoretical values. Also, the permanent dipole moments and transition dipole moments of the CH molecule are calculated at the multi-reference configuration interaction（MRCI） level. We find highly diagonally distributed FranckCondon factors（f00 = 0.9950 and 0.9998） and branching ratios（R00 = 0.983 and 0.993） for the A^2△→ X2Π and C^2∑^＋→X^2Π transitions. Moreover, the values of suitable radiative lifetime τ of the A2 A and C^2∑^＋ states are evaluated to be9.64×10^-7 s and 2.02×10^-7 s, respectively, for rapid laser cooling. A scheme for laser cooling the CH molecule is designed. In the proposed cooling scheme, three wavelengths for A^2△→X^2Π and C^2∑^＋→X^2Π transitions are used, and the main pump lasers are λ00=430.86 nm and 313.45 nm, respectively. The feasibility of laser cooling the CH molecules is demonstrated for each of these schemes, and this study offers a theoretical basis for experimental research into preparation of cold CH molecules.
基金Project supported by the Major State Basic Research Development Program of China(Grant No.2012CB921601)the National Natural Science Foundation of China(Grant Nos.11374054,11305037,11347114,and 11247283)+1 种基金the Natural Science Foundation of Fujian Province of China(Grant No.2013J01012)the Fund from Fuzhou University(Grant Nos.022513,022408,and 600891)
文摘We propose a scheme to prepare the steady-state entanglement for two atoms, which are held in separate cavities that are coupled through a short optical fiber or optical resonator. The entangled steady-state with a high fidelity can be achieved even with a low cooperativity parameter, by making use of the driving laser fields. Such a cooling mechanism is based on a resonant laser pump of the unwanted ground states to the excited states, which finally decay to the desired steady-state.
基金Project supported by Shandong Provincial Natural Science Foundation(Grant No.ZR2023LLZ003)the National Natural Science Foundation of China(Grant No.62005145)Fundamental Research Fund of Shandong University,and Shandong Provincial Postdoctoral Science Foundation(Grant No.SDBX202302002)。
文摘We demonstrate an integrating sphere to cool~(87)Rb atoms and measure the recoil-induced resonance and electromagnetically induced absorption spectrum.We measure the relationship between their linewidth and light shift with variation of the detuning and power of the cooling laser and study the performance of the diffuse laser cooling mechanism by the absorption linewidth radio?ν_E/?ν_R and light shift|?_R-?_E|using nonlinear spectroscopy.Specifically,when?ν_E/?ν_R reaches a value of 1.57,the temperature and number of cold atoms achieve the optimal cooling effect.This characterization of absorption linewidth and light shift will provide a method to estimate whether diffuse light cooling achieves the best cooling effect,contributing to the future development of isotropic laser cooling for application in quantum sensing.
基金the Natural Science Foundation of Zhejiang Province under Grant No.LZ18A040001the National Key R&D Program of China under Grant No.2018YFA0307200+2 种基金the National Natural Science Foundation of China under Grant No.12074337Zhejiang Province Plan for Science and Technology No.2020C01019the Fundamental Research Funds for the Central Universities.
文摘We extend the idea of laser cooling with adiabatic passage to multi-level type-Ⅱ transitions.We find the cooling force can be significantly enhanced when a proper magnetic field is applied.That is because the magnetic field decomposes the multi-level system into several two-level sub-systems,hence the stimulated absorption and stimulated emission can occur in order,allowing for the multiple photon momentum transfer.We show that this scheme also works on the laser-coolable molecules with a better cooling effect compared to the conventional Doppler cooling.A reduced dependence on spontaneous emission based on our scheme is observed as well.Our results suggest this scheme is very feasible for laser cooling of polar molecules.
文摘The recent progress on Raman scattering in GaN single crystals and GaN/A1N heterostructures is re- viewed. Anti-Stokes Raman scattering is used to determine electron-phonon scattering time and decay time constant for longitudinal-opticat phonons. In a typical high electron mobility transistor based on GaN/A1N heterostructures, strong resonances are reached for the first-order and second-order Raman scattering processes. Therefore, both Stokes and anti-Stokes Raman intensities are dramatically enhanced. The feasibility for laser cooling of a nitride structure is studied. A further optimization will enable us to reach the threshold for laser cooling. Raman scattering have potential applications in up-conversion lasers and laser cooling of nitride ultrafast electronic and optoelectronic devices.
基金supported by the National Natural Science Foundation of China (No.10434060 and 10674047)the Doctor Foundation of the Educational Ministry of Education of China (No.20040269010)the Shanghai Priority Academic Discipline,the 211 Foundation of the Ministry of Education of China,and the PhD Program Scholarship Fund of East China Normal University(ECNU) 2007.
文摘We propose a new method to cool the yb^3＋-doped ZBLANP glass in a standing-wave cavity. There are two advantages of this cavity-enhanced technique： the pumping power is greatly enhanced and the absorption of the cooling material is greatly increased. We introduce the basic principle of the cavity-enhanced laser cooling and discuss the cooling effect of a solid-state material in a cavity. From the theoretical study, it is found that the laser cooling effect is strongly dependent on the reflectivity of the cavity mirrors, the length of the solid material, the surface scattering of the material, and so on. Some optimal parameters for efficient laser cooling are obtained.
基金the National Key Research and Development Program of China(Grant No.2017YFA0304401)the National Development Project for Major Scientific Research Facility,China(Grant No.ZDYZ2012-2)+3 种基金the National Natural Science Foundation of China(Grant Nos.11774388 and 11634013)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030100)the CAS Youth Innovation Promotion Association(Grant Nos.2018364 and Y201963)the K.C.Wong Education Foundation(Grant No.GJTD-2019-15)。
文摘We investigate the process of pulsed laser cooling using a self-constructed molecular dynamics simulation(MDSimulation)program.We simulate the Doppler cooling process and pulsed laser Doppler cooling process of a single^(40)Ca^(+)ion,and the comparison with the experimental results shows that this self-constructed MD-Simulation program works well in the weak laser intensity situation.Furthermore,we analyze the pulsed laser Doppler cooling process of a single^(27)Al^(+)ion.This program can be used to analyze the molecular dynamic process of various situations of Doppler cooling in an ion trap,which could give predictions and experimental guidance.
基金National Natural Science Foundation of China(Grant No.51275523)and the State Key Laboratory of Aerodynamics Research Fund,China(Grant No.SKLA2019040302).
文摘We demonstrate a simple and fast way to produce 87Rb Bose–Einstein condensates. A digital optical phase lock loop(OPLL) board is introduced to lock and adjust the frequency of the trap laser, which simplifies the optical design and improves the experimental efficiency. We collect atoms in a magneto-optical trap, then compress the cloud and cut off hot atoms by rf knife in a magnetic quadrupole trap. The atom clouds are then transferred into a spatially mode-matched optical dipole trap by lowering the quadrupole field gradient. Our system reliably produces a condensate with 2 × 106 atoms every7.5 s. The compact optical design and rapid preparation speed of our system will open the gate for mobile quantum sensing.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704031)the National Science Foundation for Fostering Talents in Basic Research of the National Natural Science Foundation of China (Grant No. J0630313)+1 种基金the fundamental Research Fund for Physical and Mathematical of Lanzhou University (Grant No. Lzu05001)the Natural Science Foundation of Gansu,China (Grant No. 3ZS061-A25-035)
文摘Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. Considering Rb atoms as an example, it finds that the numerical results are relevant to the recent experimental laser cooling investigations.
基金Project supported by the National Basic Research Program of China （Grant No. 2012CB821302）, the National Natural Science Foundation of China （Grant Nos. 11134003 and 10774044）, and the Shanghai Excellent Academic Leaders Program, China （Grant No. 12XD1402400）.
文摘Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one- dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes like 172yb, Jv3yb, and J74yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are studied, and the optimal parameters for the isotope separation are also investigated. Furthermore, the isotope separation efficiency and purity are estimated. Finally a new scheme for the efficient isotope separation is proposed. These findings will give a guideline for simply obtaining pure isotopes of various elements.
文摘The use of a broadband, frequency shaped femtosecond laser on translationally cold cesium molecules has recently demonstrated to be a very efficient method of cooling also the vibrational degree of freedom. A sample of cold molecules, initially distributed over several vibrational levels, has thus been transfered into a single selected vibrational level of the singlet X^1∑g ground electronic state. Our method is based on repeated optical pumping by laser light with a spectrum broad enough to excite all populated vibrational levels but limited in its frequency bandwidth with a spatial light modulator. In such a way we are able to eliminate transitions from the selected level, in which molecules accumulate. In this paper we briefly report the main experimental results and then address, in a detailed way by computer simulations, the perspectives for a ＂complete＂ cooling of the molecules, including also the rotational degree of freedom. Since the pumping process strongly depends on the relative shape of the ground and excited potential curves, ro-vibrational cooling through different excited states is theoretically compared.
文摘Doppler cooling of^(88)Sr atoms is studied in the presence of off-resonant red-detuned fluctuating laser fields.Using a semi-classical approach,we show that the relevant physical quantities in the cooling process,such as optical forces,the damping coefficient,Doppler temperature,and atom number in the trap,are strongly affected by the laser amplitude and phase fluctuations.We find that the Doppler cooling limit is higher than the predicted Doppler theory for non-fluctuating lasers.This implies an additional heating mechanism exists due to the laser fluctuations.Furthermore,our numerical analysis shows that the effect of laser power stability on reducing the number of trapped atoms in a magneto-optical trap is more substantial than the effect of laser linewidth.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0304503)Key Research and Development Project of Guangdong Province,China(Grant No.2020B030300001)the National Natural Science Foundation of China(Grant Nos.828330256,11636220,11805279,1173401,and 11504430)。
文摘We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possible to cool a resonator to its ground state in the strong cavity-atom coupling regime.Moreover,with the assistance of one additional energy level,our scheme takes a larger cooling rate to realize the ground state cooling.In addition,this scheme is a feasible candidate for experimental applications.
