The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated...The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated by a variational approach within mean-field theory. We derive an extended Bos^Hubbard model to describe this ultracold atomic system. By theoretical calculation and analysis, the phase diagram is shown clearly, and we find an exciting and novel phenomenon that is the appearance of the Mort insulator-sea （MI-sea）. Meanwhile, the experimental feasibility of observing the MI-sea is discussed by analyzing the published data related to the Fashbaeh resonance at present. Finally, the potential application of the MI-sea for quantum information processing and quantum computation is also discussed in detail展开更多
A novel idea is proposed to suppress the soliton self-frequency shift of femtosecond soliton pulse in dispersion-decreasing fibers.The expression of the soliton self-frequency shift as a function of the pulse width an...A novel idea is proposed to suppress the soliton self-frequency shift of femtosecond soliton pulse in dispersion-decreasing fibers.The expression of the soliton self-frequency shift as a function of the pulse width and the fiber dispersion parameter is derived.The numerical simulation is also given,and is in agreement with analytical results.展开更多
We investigate the adiabatic enhanced compression of ultrashort pulses from a distributed feedback laser operated at 1550 nm in fibres with slowly decreasing dispersion (FSDD). High-quality pulse compressions from 4.4...We investigate the adiabatic enhanced compression of ultrashort pulses from a distributed feedback laser operated at 1550 nm in fibres with slowly decreasing dispersion (FSDD). High-quality pulse compressions from 4.4 ps down to 1.1ps in a l00m FSDD and from 4.4ps down to 830fs in a 500m FSDD are obtained. The Raman self frequency shift of femtosecond pulses in the compression is observed. Theoretical analyses are in good agreement with experimental results.展开更多
The experimental scheme of 633 nm and 1359 nm good-bad cavity dual-wavelength active optical frequency stan- dard is proposed, where He-Ne 633nm and Cs 1359nm stimulated emissions are working at good-cavity and bad-ca...The experimental scheme of 633 nm and 1359 nm good-bad cavity dual-wavelength active optical frequency stan- dard is proposed, where He-Ne 633nm and Cs 1359nm stimulated emissions are working at good-cavity and bad-cavity regimes, respectively. The cavity length is stabilized by locking the 633nm output frequency to a super-cavity with the Pound Drever-Hall （PDH） technique. The frequency stability of 1359 nm bad-cavity stim- ulated emission output is then expected to be further improved by at least 1 order of magnitude than the 633nm PDH system due to the suppressed cavity pulling effect of active optical clock, and the quantum limited linewidth of 1359nm output is estimated to be 72.5 mHz.展开更多
Significant high magnetic gradient field strength is essential to obtaining high-resolution images in a benchtop mag- netic resonance imaging （BT-MRI） system with permanent magnet. Extending minimum wire spacing and...Significant high magnetic gradient field strength is essential to obtaining high-resolution images in a benchtop mag- netic resonance imaging （BT-MRI） system with permanent magnet. Extending minimum wire spacing and maximum wire width of gradient coils is one of the key solutions to minimize the maximum current density so as to reduce the local heating and generate higher magnetic field gradient strength. However, maximum current density is hard to optimize together with field linearity, stored magnetic energy, and power dissipation by the traditional target field method. In this paper, a new multi-objective method is proposed to optimize the maximum current density, field linearity, stored magnetic energy, and power dissipation in MRI gradient coils. The simulation and experimental results show that the minimum wire spacings are improved by 159% and 62% for the transverse and longitudinal gradient coil respectively. The maximum wire width increases from 0.5 mm to 1.5 mm. Maximum gradient field strengths of 157 mT/m and 405 mT/m for transverse and lon- gitudinal coil are achieved, respectively. The experimental results in BT-MRI instrument demonstrate that the MRI images with in-plane resolution of 50 ~tm can be obtained by using the designed coils.展开更多
We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% a...We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% and the transform limited pulse width is reduced almost by half, compared with those obtained with hollow fibres in uniform temperature.展开更多
A new region where modulation stability occurs in the fibers with minimum group-velocity was found due to the fourth-order dispersion effect.The spectral extent of the region is analyzed and found to be affected by in...A new region where modulation stability occurs in the fibers with minimum group-velocity was found due to the fourth-order dispersion effect.The spectral extent of the region is analyzed and found to be affected by initial input power and the dispersion parameter.展开更多
The population ratio between the excited states of rubidium in the electrodeless discharge rubidium vapour lamp is calculated according to the near-infrared spectra in the region of 780-1550 nm. By using a 1529 nm las...The population ratio between the excited states of rubidium in the electrodeless discharge rubidium vapour lamp is calculated according to the near-infrared spectra in the region of 780-1550 nm. By using a 1529 nm laser, we measure the density of natural rubidium atoms at the 5P3/2 level. The populations of different excited states are then clarified.展开更多
The influence of the third-order dispersion (TOD) on the polarization mode dispersion (PMD) is investigated. It is found that the TOD effect destroys orthogonal polarization modes in optical birefringent fibres. A new...The influence of the third-order dispersion (TOD) on the polarization mode dispersion (PMD) is investigated. It is found that the TOD effect destroys orthogonal polarization modes in optical birefringent fibres. A new method is proposed to compensate for the PMD by means of cascading the fibres with the positive and negative TOD. This has proven to be practicable in long transmissions.展开更多
The absolute frequency of 87Rb 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition at 778nm is measured in an accuracy of 44kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of 5.0 ...The absolute frequency of 87Rb 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition at 778nm is measured in an accuracy of 44kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of 5.0 × 10-13@1 s is employed for the light source. By using a periodically poled lithium niobate, the femtosecond pulse operating in 1556 nm is frequency-doubled to 778 nm to obtain the direct two-photon transition spectroscopy of thermal rubidium vapor. Through sweeping the carrier envelope offset frequency （fceo）, the 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition line is clearly resolved and its absolute frequency is determined via the peak-finding of the fitting curve. After the frequency correction, the measured result agrees well with the previous experiment on this transition. The entire potential candidate of optical frequency standard for system configuration is compact and robust, providing a telecommunication applications.展开更多
The collapse and revival of evolution with photon number of population inversion in the case of an atomic beam with velocity distribution interacting with a single-mode and Fock-state light field is investigated by fu...The collapse and revival of evolution with photon number of population inversion in the case of an atomic beam with velocity distribution interacting with a single-mode and Fock-state light field is investigated by full quantum theory. Compared to the previously reported coherent state case [Li B and Chen J B Chin. Phys. Lett. 26（2009）123203], which was induced by evolution with coupling strength of population inversion, in the case under consideration there exists Poisson distribution of photon numbers and atomic velocity distribution in the beam. Moreover, we prove that above, the collapse and revival have an analogy with conventional collapse and revival [Eberly J H et al. Phys. Rev. Lett. 44（1980）1323] in both the mathematical expression and physical significance.展开更多
In clinical magnetic resonance imaging （MRI）, the design of the radiofrequency （RF） coil is very important. For certain applications, the appropriate coil can produce an improved image quality. However, it is diff...In clinical magnetic resonance imaging （MRI）, the design of the radiofrequency （RF） coil is very important. For certain applications, the appropriate coil can produce an improved image quality. However, it is difficult to achieve a uniform B1 field and a high signal-to-noise ratio （SNR） simultaneously. In this article, we design an interventional transmitter-and-receiver RF coil for cerebral surgery. This coil adopts a disassembly structure that can be assembled and disassembled repeatedly on the cerebral surgery gantry to reduce the amount of interference from the MRI during surgery. The simulation results and the imaging experiments demonstrate that this coil can produce a uniform RF field, a high SNR, and a large imaging range to meet the requirements of the cerebral surgery.展开更多
The kinetic theory of （2＋4）-level atoms in σ^＋ -σ^- laser fields is presented. We systemically discuss friction coefficient, momentum diffusion tensor and atomic temperature based on the Fokker-Planck equation. ...The kinetic theory of （2＋4）-level atoms in σ^＋ -σ^- laser fields is presented. We systemically discuss friction coefficient, momentum diffusion tensor and atomic temperature based on the Fokker-Planck equation. This cooling system is much like that of a （1＋3）-level atom, and the temperature is still limited to the Doppler temperature. Since this cooling system has not been investigated before, this work may be regarded as a necessary complement to the laser cooling theory.展开更多
We propose an experimental scheme of vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)optical frequency standards with noble gas atoms.Considering metastable state 3𝑃2 noble atoms pumped by a conventional di...We propose an experimental scheme of vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)optical frequency standards with noble gas atoms.Considering metastable state 3𝑃2 noble atoms pumped by a conventional discharging method,the atomic beam is collimated with transverse laser cooling at the metastable state and enters into the laser cavity in the proposed setup.Due to stimulated emission from the metasable state to the ground state inside the laser cavity consisting of VUV reflection coating mirrors,our calculations show that with enough population inversion to compensate for the cavity loss,an active optical frequency standard at VUV and XUV is feasible.展开更多
A further study is conducted on two factors which respectively influence the sensitivity of optically pumped cesium magnetometer （CsOPM）. The influence of radio frequency （RF） power and the buffer gas pressure on ...A further study is conducted on two factors which respectively influence the sensitivity of optically pumped cesium magnetometer （CsOPM）. The influence of radio frequency （RF） power and the buffer gas pressure on the sensitivity is theoretically analyzed, and some properties are predicted. Based on the established measurement system and the visible Zeeman spectrum, not only is the real influence of these factors studied, but also, under our experimental condition, optimum parameters based on the measured curves are ascertained. The properties of these measured curves match the theoretical result very well. Our research attempts to provide theory reference to help magnetometer designers determine optimum parameters under certain conditions.展开更多
Two-dimensional(2D)nuclear magnetic resonance(NMR)distributions as functions of diffusion coefficient and relaxation time are powerful tools in the study of porous media.We propose a practical method to perform proper...Two-dimensional(2D)nuclear magnetic resonance(NMR)distributions as functions of diffusion coefficient and relaxation time are powerful tools in the study of porous media.We propose a practical method to perform proper truncation of singular value decomposition(TSVD)in Laplace inversion for obtaining 2D-NMR distributions from measured NMR data.By analyzing basic algorithms for Laplace inversion,it is well known that proper TSVD does not affect the inversion result for an ill-posed problem with zero-order Tikhonov regularization,but can greatly increase the inversion speed.In this new method,the optimal number of singular values for data compression is applied to each dimension separately.The method also makes full use of the redundancy nature of the data with a finite signal-to-noise ratio and well balances the tradeoff between the speed and the bias.The method does not require the stochastic information of the estimated parameters when obtaining the optimal number of singular values.展开更多
The optical frequency comb has been widely used in precision measurement. In this study, a multi-peak fitting approach is first proposed to fit the two-photon transition spectrum which overlaps with the neighboring tr...The optical frequency comb has been widely used in precision measurement. In this study, a multi-peak fitting approach is first proposed to fit the two-photon transition spectrum which overlaps with the neighboring transition in Rb-87. The multi-peak fitting approach is used to eliminate the frequency shift affected by the neighboring transition. With locking the carrier envelope offset frequency at 1/4 repetition frequency, the transition frequency is measured to be 770569132739.9 +/- 5.8 kHz, which agrees well with the previous result recommended by Comite International des Poids et Mesures.展开更多
The time evolution of populations of the ground state hyperfine Zeeman levels of ^(87)Rb atoms is analyzed using the Runge-Kutta method for the case that a rubidium beam is optically pumped,under different conditions ...The time evolution of populations of the ground state hyperfine Zeeman levels of ^(87)Rb atoms is analyzed using the Runge-Kutta method for the case that a rubidium beam is optically pumped,under different conditions of polarization,with a weak monochromatic laser and an ^(87)R lamp.On the base of the results above,the least estimated laser and ^(87)R lamp power for the best population inversion is obtained,aiding further investigations.展开更多
Starting from our definition of apodization profile functions,we discover the optimal profiles and the characteristics of defined apodization functions in sidelobe suppression.It is shown by numerical analysis that th...Starting from our definition of apodization profile functions,we discover the optimal profiles and the characteristics of defined apodization functions in sidelobe suppression.It is shown by numerical analysis that the optimal grating length is 45 mm to compensate for dispersion induced by 100 km fibres and the smoothness of the ripples in time-delay characteristics is related to the defined parameters.展开更多
We report on the phenomena of the periodic spontaneous collapse and revival in the dynamics of an atomic beam interacting with a single-mode and coherent-state light field. Conventional collapse and revival by Eberly ...We report on the phenomena of the periodic spontaneous collapse and revival in the dynamics of an atomic beam interacting with a single-mode and coherent-state light field. Conventional collapse and revival by Eberly et al. [Phys. Rev. Lett. 44（1980）1323 ] are presented in the case of the evolution with time of the population inversion. Here, we study the evolution with coupling strength of population inversion. We define the collapse and revival coupling strengths as characteristic parameters to describe the above collapse and revival. Furthermore, we present the analytic formulas for the population inversion, the collapse and revival coupling strengths.展开更多
基金Supported by the National Basic Research Program of China under Grant No 2005CB724500, the National Natural Science Foundation of China under No 140874009, and the Open Research Found of State Key Laboratory of Precision Spectroscopy （East China Normal University）.
文摘The quantum phase transition from the Mott insulator to the superfluid phases of the bosonic atoms trapped in an optical lattice, in which the on-site interaction carl be tuned by a Feshbach resonance, is investigated by a variational approach within mean-field theory. We derive an extended Bos^Hubbard model to describe this ultracold atomic system. By theoretical calculation and analysis, the phase diagram is shown clearly, and we find an exciting and novel phenomenon that is the appearance of the Mort insulator-sea （MI-sea）. Meanwhile, the experimental feasibility of observing the MI-sea is discussed by analyzing the published data related to the Fashbaeh resonance at present. Finally, the potential application of the MI-sea for quantum information processing and quantum computation is also discussed in detail
文摘A novel idea is proposed to suppress the soliton self-frequency shift of femtosecond soliton pulse in dispersion-decreasing fibers.The expression of the soliton self-frequency shift as a function of the pulse width and the fiber dispersion parameter is derived.The numerical simulation is also given,and is in agreement with analytical results.
基金Supported by the Natural Science Foundation of the Guangdong Education Department(200019)the Natural Science Foundation of Guangdong Province(980030).
文摘We investigate the adiabatic enhanced compression of ultrashort pulses from a distributed feedback laser operated at 1550 nm in fibres with slowly decreasing dispersion (FSDD). High-quality pulse compressions from 4.4 ps down to 1.1ps in a l00m FSDD and from 4.4ps down to 830fs in a 500m FSDD are obtained. The Raman self frequency shift of femtosecond pulses in the compression is observed. Theoretical analyses are in good agreement with experimental results.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10874009,11074011 and 91436210the International Science&Technology Cooperation Program of China under Grant No 2010DFR10900
文摘The experimental scheme of 633 nm and 1359 nm good-bad cavity dual-wavelength active optical frequency stan- dard is proposed, where He-Ne 633nm and Cs 1359nm stimulated emissions are working at good-cavity and bad-cavity regimes, respectively. The cavity length is stabilized by locking the 633nm output frequency to a super-cavity with the Pound Drever-Hall （PDH） technique. The frequency stability of 1359 nm bad-cavity stim- ulated emission output is then expected to be further improved by at least 1 order of magnitude than the 633nm PDH system due to the suppressed cavity pulling effect of active optical clock, and the quantum limited linewidth of 1359nm output is estimated to be 72.5 mHz.
基金Project supported by the Natural Science Foundation of the Ministry of Science and Technology of China (Grant No.2011ZX05008004)the Science Fund of the Committee of Science and Technology of Beijing,China
文摘Significant high magnetic gradient field strength is essential to obtaining high-resolution images in a benchtop mag- netic resonance imaging （BT-MRI） system with permanent magnet. Extending minimum wire spacing and maximum wire width of gradient coils is one of the key solutions to minimize the maximum current density so as to reduce the local heating and generate higher magnetic field gradient strength. However, maximum current density is hard to optimize together with field linearity, stored magnetic energy, and power dissipation by the traditional target field method. In this paper, a new multi-objective method is proposed to optimize the maximum current density, field linearity, stored magnetic energy, and power dissipation in MRI gradient coils. The simulation and experimental results show that the minimum wire spacings are improved by 159% and 62% for the transverse and longitudinal gradient coil respectively. The maximum wire width increases from 0.5 mm to 1.5 mm. Maximum gradient field strengths of 157 mT/m and 405 mT/m for transverse and lon- gitudinal coil are achieved, respectively. The experimental results in BT-MRI instrument demonstrate that the MRI images with in-plane resolution of 50 ~tm can be obtained by using the designed coils.
基金Supported by the National Basic Research Programme of China under Grant No 2006CB806000, the National Natural Science Foundation of China under Grant Nos 60490280 and 60578007, NSFC-JSPS International Cooperation Programme under Grant No 60611140297, the Tianjin Natural Science Foundation under Grant No 07JCYBJC15500.
文摘We propose a novel technique for generating intense few to mono-cycle femtosecond pulses. The simulation demonstrate that for the temperature difference of 300K, the spectrum of the output pulses is increased by 67% and the transform limited pulse width is reduced almost by half, compared with those obtained with hollow fibres in uniform temperature.
基金Supported by the National“Climb”Program,and Natural Science Foundation of Guangdong Province。
文摘A new region where modulation stability occurs in the fibers with minimum group-velocity was found due to the fourth-order dispersion effect.The spectral extent of the region is analyzed and found to be affected by initial input power and the dispersion parameter.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10874009 and 11074011)
文摘The population ratio between the excited states of rubidium in the electrodeless discharge rubidium vapour lamp is calculated according to the near-infrared spectra in the region of 780-1550 nm. By using a 1529 nm laser, we measure the density of natural rubidium atoms at the 5P3/2 level. The populations of different excited states are then clarified.
基金Supported by the Natural Science Foundation of Guangdong Province under Grant Nos.980030 and 200019。
文摘The influence of the third-order dispersion (TOD) on the polarization mode dispersion (PMD) is investigated. It is found that the TOD effect destroys orthogonal polarization modes in optical birefringent fibres. A new method is proposed to compensate for the PMD by means of cascading the fibres with the positive and negative TOD. This has proven to be practicable in long transmissions.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61405002,91336103,10934010,61535001 and 61078026
文摘The absolute frequency of 87Rb 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition at 778nm is measured in an accuracy of 44kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of 5.0 × 10-13@1 s is employed for the light source. By using a periodically poled lithium niobate, the femtosecond pulse operating in 1556 nm is frequency-doubled to 778 nm to obtain the direct two-photon transition spectroscopy of thermal rubidium vapor. Through sweeping the carrier envelope offset frequency （fceo）, the 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition line is clearly resolved and its absolute frequency is determined via the peak-finding of the fitting curve. After the frequency correction, the measured result agrees well with the previous experiment on this transition. The entire potential candidate of optical frequency standard for system configuration is compact and robust, providing a telecommunication applications.
基金Supported by the National Basic Research Program of China under Grant No 2005CB724500the National Natural Science Foundation of China under No 10874009Open Research Found of State Key Laboratory of Precision Spectroscopy(East China Normal University).
文摘The collapse and revival of evolution with photon number of population inversion in the case of an atomic beam with velocity distribution interacting with a single-mode and Fock-state light field is investigated by full quantum theory. Compared to the previously reported coherent state case [Li B and Chen J B Chin. Phys. Lett. 26（2009）123203], which was induced by evolution with coupling strength of population inversion, in the case under consideration there exists Poisson distribution of photon numbers and atomic velocity distribution in the beam. Moreover, we prove that above, the collapse and revival have an analogy with conventional collapse and revival [Eberly J H et al. Phys. Rev. Lett. 44（1980）1323] in both the mathematical expression and physical significance.
文摘In clinical magnetic resonance imaging （MRI）, the design of the radiofrequency （RF） coil is very important. For certain applications, the appropriate coil can produce an improved image quality. However, it is difficult to achieve a uniform B1 field and a high signal-to-noise ratio （SNR） simultaneously. In this article, we design an interventional transmitter-and-receiver RF coil for cerebral surgery. This coil adopts a disassembly structure that can be assembled and disassembled repeatedly on the cerebral surgery gantry to reduce the amount of interference from the MRI during surgery. The simulation results and the imaging experiments demonstrate that this coil can produce a uniform RF field, a high SNR, and a large imaging range to meet the requirements of the cerebral surgery.
基金supported by the National Fundamental Research Programme of China (Grants No 2005CB724500)
文摘The kinetic theory of （2＋4）-level atoms in σ^＋ -σ^- laser fields is presented. We systemically discuss friction coefficient, momentum diffusion tensor and atomic temperature based on the Fokker-Planck equation. This cooling system is much like that of a （1＋3）-level atom, and the temperature is still limited to the Doppler temperature. Since this cooling system has not been investigated before, this work may be regarded as a necessary complement to the laser cooling theory.
基金by the National Natural Science Foundation of China under Grant No 10874009.
文摘We propose an experimental scheme of vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)optical frequency standards with noble gas atoms.Considering metastable state 3𝑃2 noble atoms pumped by a conventional discharging method,the atomic beam is collimated with transverse laser cooling at the metastable state and enters into the laser cavity in the proposed setup.Due to stimulated emission from the metasable state to the ground state inside the laser cavity consisting of VUV reflection coating mirrors,our calculations show that with enough population inversion to compensate for the cavity loss,an active optical frequency standard at VUV and XUV is feasible.
基金Project supported by the National Natural Science Foundation of China(Grant No.11174015)
文摘A further study is conducted on two factors which respectively influence the sensitivity of optically pumped cesium magnetometer （CsOPM）. The influence of radio frequency （RF） power and the buffer gas pressure on the sensitivity is theoretically analyzed, and some properties are predicted. Based on the established measurement system and the visible Zeeman spectrum, not only is the real influence of these factors studied, but also, under our experimental condition, optimum parameters based on the measured curves are ascertained. The properties of these measured curves match the theoretical result very well. Our research attempts to provide theory reference to help magnetometer designers determine optimum parameters under certain conditions.
基金Supported by the National Key Project of the Ministry of Science and Technology of China under Grant No 2011ZX05008-004.
文摘Two-dimensional(2D)nuclear magnetic resonance(NMR)distributions as functions of diffusion coefficient and relaxation time are powerful tools in the study of porous media.We propose a practical method to perform proper truncation of singular value decomposition(TSVD)in Laplace inversion for obtaining 2D-NMR distributions from measured NMR data.By analyzing basic algorithms for Laplace inversion,it is well known that proper TSVD does not affect the inversion result for an ill-posed problem with zero-order Tikhonov regularization,but can greatly increase the inversion speed.In this new method,the optimal number of singular values for data compression is applied to each dimension separately.The method also makes full use of the redundancy nature of the data with a finite signal-to-noise ratio and well balances the tradeoff between the speed and the bias.The method does not require the stochastic information of the estimated parameters when obtaining the optimal number of singular values.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91336103,10934010 and 61078026
文摘The optical frequency comb has been widely used in precision measurement. In this study, a multi-peak fitting approach is first proposed to fit the two-photon transition spectrum which overlaps with the neighboring transition in Rb-87. The multi-peak fitting approach is used to eliminate the frequency shift affected by the neighboring transition. With locking the carrier envelope offset frequency at 1/4 repetition frequency, the transition frequency is measured to be 770569132739.9 +/- 5.8 kHz, which agrees well with the previous result recommended by Comite International des Poids et Mesures.
基金Supported by the National Natural Science Foundation of China under Grant No 11174015the Fundamental Research Funds for the Central Universities.
文摘The time evolution of populations of the ground state hyperfine Zeeman levels of ^(87)Rb atoms is analyzed using the Runge-Kutta method for the case that a rubidium beam is optically pumped,under different conditions of polarization,with a weak monochromatic laser and an ^(87)R lamp.On the base of the results above,the least estimated laser and ^(87)R lamp power for the best population inversion is obtained,aiding further investigations.
基金Supported by 863 National High Technology Research Plan(863-307-15)Tianjin Natural Science Foundation(003600811)China Postdoctoral Science Foundation and Huawei Scientific Research Foundation.
文摘Starting from our definition of apodization profile functions,we discover the optimal profiles and the characteristics of defined apodization functions in sidelobe suppression.It is shown by numerical analysis that the optimal grating length is 45 mm to compensate for dispersion induced by 100 km fibres and the smoothness of the ripples in time-delay characteristics is related to the defined parameters.
基金Supported by the National Basic Research Program of China under Grant No 2005CB724500, the National Natural Science Foundation of China under No 10874009, and Open Research Found of State Key Laboratory of Precision Spectroscopy （East China Normal University）.
文摘We report on the phenomena of the periodic spontaneous collapse and revival in the dynamics of an atomic beam interacting with a single-mode and coherent-state light field. Conventional collapse and revival by Eberly et al. [Phys. Rev. Lett. 44（1980）1323 ] are presented in the case of the evolution with time of the population inversion. Here, we study the evolution with coupling strength of population inversion. We define the collapse and revival coupling strengths as characteristic parameters to describe the above collapse and revival. Furthermore, we present the analytic formulas for the population inversion, the collapse and revival coupling strengths.
