In this paper, we discuss and analyze theoretically probeabsorption-amplification response in a four-level coherent atomic system with vacuum-inducedcoherence via changing the sign of the parameter f, with f denoting ...In this paper, we discuss and analyze theoretically probeabsorption-amplification response in a four-level coherent atomic system with vacuum-inducedcoherence via changing the sign of the parameter f, with f denoting the ratio of a pair of dipolemoments associated with a doublet of closely upper hypernne sublevels. We find that the amplitude ofthe probe amplification for the case f = -1 can be about one order of magnitude larger than thatachievable for the case f = 1. In addition, with respect to the case f = -1 the probe amplificationcan be maintained all the time with weak incoherent pumping for a wide range of the probe detuning.展开更多
Sideband manipulation of population inversion in a three-level A atomic configuration is investigated theoretically. Compared with the case of a nearly monochromatic field, a population inversion between an excited st...Sideband manipulation of population inversion in a three-level A atomic configuration is investigated theoretically. Compared with the case of a nearly monochromatic field, a population inversion between an excited state and a ground state has been found in a wide sideband intensity range by increasing the difference in frequency between three components. Furthermore, the population inversion can be controlled by the sum of the relative phases of the sideband components of the trichromatic pump field with respective to the phase of the central component. Changing the sum phase from 0 to π, the population inversion between the excited state and the ground state can increase within nearly half of the sideband intensity range. At the same time, the sideband intensity range that corresponds to the system exhibiting inversion ρ00 〉 ρ11 also becomes wider evidently.展开更多
We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level the...We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level theoretically with the density matrix method.In a steady state,5.8% atoms are at 7S1/2 level and 2.9% at 6P3/2 level,which builds up the population inversion between the two levels.We obtain the fluorescence spectra produced in thermal cesium cell in our experiment.The measured relative intensity of each available fluorescence spectral line in the experiment agrees very well with the theoretical result.The demonstrated population inversion between 7S1/2 and 6P3/2 levels can be used to construct an active optical clock of four-level system with a wavelength of 1469.9 nm.展开更多
A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition （PIC） of the active region （AR） and discuss the PICs on diff...A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition （PIC） of the active region （AR） and discuss the PICs on different structures by changing structural parameters such as the widths of quantum wells or barriers in the AR. For some instances, the PIC can be simplified and is proportional to the spontaneous emission lifetime between the second and the first excited states, whereas some other instances imply that the PIC is proportional to the state lifetime of the second excited state.展开更多
In this paper we present a general theoretical model for the interaction between a number of two-level atoms constituting Bose-Einstein condensate （BEG） and a single-mode quantized field. In addition to the usual in...In this paper we present a general theoretical model for the interaction between a number of two-level atoms constituting Bose-Einstein condensate （BEG） and a single-mode quantized field. In addition to the usual interacting terms, we take into account interatom as well as higher-order atom-field interactions. To simplify the Hamiltonian of system, after using the Bogoliubov approximation we proceed to calculate the transformed operators of atoms and field. Then, to quantify the spontaneous emission, we get analytical expressions for the expectation value of Jz as the atomic population inversion （API）, in the cases of number and coherent states for the atomic subsystem. Our results show that the above-mentioned model interaction leads to the appearance of collapse-revival phenomenon in API. In more detail, the revival time may be tuned by adjusting the interatom interaction constant. Also, the damping process lowers the amplitude of API, but does not change the CR times for weak damping. Moreover, increasing the damping may decrease the number of CRs in a given interval of time such that no revival occurs. Briefly, it may be concluded that in the resonant case the revival times are insensitive to the change of the higher-order atom-field interaction constant and are affected only by the interatom interactions. Finally, we express that, how we can find a practical procedure to measure the quantum states of atoms in BEG.展开更多
We report a new coherence and interference phenomenon in a V-type system with an external field coupling two upper levels. It is found that the probe gain can be generated even when no probe field is applied to the sy...We report a new coherence and interference phenomenon in a V-type system with an external field coupling two upper levels. It is found that the probe gain can be generated even when no probe field is applied to the system, we attribute this result to the existence of the external field. By comparing with the conventional probe gain, the probe gain without the probe field is enhanced greatly because of the absence of the population inversion term.展开更多
We present a theoretical study of electromagnetically induced transparency （EIT） in a superconducting quantum circuit with a tunable V-shaped energy spectrum derived from two superconducting Josephson charge qubits ...We present a theoretical study of electromagnetically induced transparency （EIT） in a superconducting quantum circuit with a tunable V-shaped energy spectrum derived from two superconducting Josephson charge qubits coupled with each other through a superconducting quantum interference device. Using the density matrix formalism and the steady-state approximation, we obtain the analytical expressions of the first-order matrix element associated with the absorption and dispersion of the probe field for two different V-type schemes. Our results show that, for this superconducting quantum system, it is possible to realize a remarkable phenomenon that dynamic conversion between EIT and EIT with amplification without population inversion. Such a unique optical feature has potential applications in quantum optical devices and quantum information processing.展开更多
Energy levels, transition probability and oscillator strengths have been calculated for the Ar XIII, Ti XVII and Fe XXI. The configurations included in the calculations are 2s<sup>2</sup> 2p<sup>2<...Energy levels, transition probability and oscillator strengths have been calculated for the Ar XIII, Ti XVII and Fe XXI. The configurations included in the calculations are 2s<sup>2</sup> 2p<sup>2</sup>, 2s<sup>2</sup> 2p 3l (l = s, p & d) and 4l (l = s, p, d, & f) of C-like Ar XIII, Ti XVII & Fe XXI which has 69 fine structures by using the fully relativistic flexible atomic code (FAC) program. These data are used in the determination of the reduced population and gain coefficients over a wide range of electron densities from (10<sup>+18</sup> to 10<sup>+23</sup>) and at various plasmas temperatures. The results show that the transitions in Ar<sup>18+</sup>, Ti<sup>22+</sup>, and Fe<sup>26+</sup> ions are the most promising laser emission lines in the XUV and soft X-ray spectral regions.展开更多
Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the ...Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the formidable requirement of population inversion at short wavelengths.Rare-earth(RE)-activated microcavities,featuring highquality factor(Q)and small mode volume of whispering gallery modes,offer a great opportunity for achieving infrared-to-visible upconversion(UC)lasing.Here,we report that batch-produced nano-glass composite(GC)microspheres incorporating RE-doped fluoride nanocrystals show efficient UC emissions.These multi-phase composite microspheres exhibit a high Q value(≥10^(5)),comparable to that of conventional multi-component glass microspheres.The UC lasing with pure red,green,and blue(RGB)emissions are demonstrated based on a highly efficient tapered fiber-microsphere system.More importantly,the GC microspheres manifest reduced(by 45%)lasing threshold and enhanced(more than four times)slope effciency.These characteristics,together with excellent long-term stability,suggest a promising solution to achieving highly robust,stand-alone,low-threshold,and versatile UC microlasers.展开更多
We investigate the dynamics of a system that consists of ultra-cold three-level atoms interacting with radiation fields.We derive the analytical expressions for the population dynamics of the system,particularly,in th...We investigate the dynamics of a system that consists of ultra-cold three-level atoms interacting with radiation fields.We derive the analytical expressions for the population dynamics of the system,particularly,in the presence and absence of nonlinear collisions by considering the rotating wave approximation(RWA).We also reanalyze the dynamics of the system beyond RWA and obtain the state vector of the system to study and compare the time behavior of population inversion.Our results show that the system undergoes two pure quantum phenomena,i.e.,the collapse-revival and macroscopic quantum self-trapping due to nonlinear collisional interactions.The occurrence of such phenomena strongly depends on the number of atoms in the system and also the ratio of interaction strengths in the considered system.Finally,we show that the result of the perturbed time evolution operator up to the second-order is in agreement with the numerical solution of the Schrodinger equation.The results presented in the paper may be useful for the design of devices that produce a coherent beam of bosonic atoms known as an atom laser.展开更多
文摘In this paper, we discuss and analyze theoretically probeabsorption-amplification response in a four-level coherent atomic system with vacuum-inducedcoherence via changing the sign of the parameter f, with f denoting the ratio of a pair of dipolemoments associated with a doublet of closely upper hypernne sublevels. We find that the amplitude ofthe probe amplification for the case f = -1 can be about one order of magnitude larger than thatachievable for the case f = 1. In addition, with respect to the case f = -1 the probe amplificationcan be maintained all the time with weak incoherent pumping for a wide range of the probe detuning.
基金Project supported by the National Natural Science Foundation of China (Grant No 60708008)the Project of Academic Leaders in Shanghai,China (Grant No 07XD14030)the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘Sideband manipulation of population inversion in a three-level A atomic configuration is investigated theoretically. Compared with the case of a nearly monochromatic field, a population inversion between an excited state and a ground state has been found in a wide sideband intensity range by increasing the difference in frequency between three components. Furthermore, the population inversion can be controlled by the sum of the relative phases of the sideband components of the trichromatic pump field with respective to the phase of the central component. Changing the sum phase from 0 to π, the population inversion between the excited state and the ground state can increase within nearly half of the sideband intensity range. At the same time, the sideband intensity range that corresponds to the system exhibiting inversion ρ00 〉 ρ11 also becomes wider evidently.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10874009 and 11074011)
文摘We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level theoretically with the density matrix method.In a steady state,5.8% atoms are at 7S1/2 level and 2.9% at 6P3/2 level,which builds up the population inversion between the two levels.We obtain the fluorescence spectra produced in thermal cesium cell in our experiment.The measured relative intensity of each available fluorescence spectral line in the experiment agrees very well with the theoretical result.The demonstrated population inversion between 7S1/2 and 6P3/2 levels can be used to construct an active optical clock of four-level system with a wavelength of 1469.9 nm.
基金supported by the National Natural Science Foundation of China(No.60976070)the Special Funds of China Academy of Engineering Physics(No.909)
文摘A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition （PIC） of the active region （AR） and discuss the PICs on different structures by changing structural parameters such as the widths of quantum wells or barriers in the AR. For some instances, the PIC can be simplified and is proportional to the spontaneous emission lifetime between the second and the first excited states, whereas some other instances imply that the PIC is proportional to the state lifetime of the second excited state.
文摘In this paper we present a general theoretical model for the interaction between a number of two-level atoms constituting Bose-Einstein condensate （BEG） and a single-mode quantized field. In addition to the usual interacting terms, we take into account interatom as well as higher-order atom-field interactions. To simplify the Hamiltonian of system, after using the Bogoliubov approximation we proceed to calculate the transformed operators of atoms and field. Then, to quantify the spontaneous emission, we get analytical expressions for the expectation value of Jz as the atomic population inversion （API）, in the cases of number and coherent states for the atomic subsystem. Our results show that the above-mentioned model interaction leads to the appearance of collapse-revival phenomenon in API. In more detail, the revival time may be tuned by adjusting the interatom interaction constant. Also, the damping process lowers the amplitude of API, but does not change the CR times for weak damping. Moreover, increasing the damping may decrease the number of CRs in a given interval of time such that no revival occurs. Briefly, it may be concluded that in the resonant case the revival times are insensitive to the change of the higher-order atom-field interaction constant and are affected only by the interatom interactions. Finally, we express that, how we can find a practical procedure to measure the quantum states of atoms in BEG.
基金Supported by National Natural Science Foundation of China under Grant Nos.10904015,11004030,and 11074036
文摘We report a new coherence and interference phenomenon in a V-type system with an external field coupling two upper levels. It is found that the probe gain can be generated even when no probe field is applied to the system, we attribute this result to the existence of the external field. By comparing with the conventional probe gain, the probe gain without the probe field is enhanced greatly because of the absence of the population inversion term.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274132)the Natural Science Foundation of Hubei Province,China
文摘We present a theoretical study of electromagnetically induced transparency （EIT） in a superconducting quantum circuit with a tunable V-shaped energy spectrum derived from two superconducting Josephson charge qubits coupled with each other through a superconducting quantum interference device. Using the density matrix formalism and the steady-state approximation, we obtain the analytical expressions of the first-order matrix element associated with the absorption and dispersion of the probe field for two different V-type schemes. Our results show that, for this superconducting quantum system, it is possible to realize a remarkable phenomenon that dynamic conversion between EIT and EIT with amplification without population inversion. Such a unique optical feature has potential applications in quantum optical devices and quantum information processing.
文摘Energy levels, transition probability and oscillator strengths have been calculated for the Ar XIII, Ti XVII and Fe XXI. The configurations included in the calculations are 2s<sup>2</sup> 2p<sup>2</sup>, 2s<sup>2</sup> 2p 3l (l = s, p & d) and 4l (l = s, p, d, & f) of C-like Ar XIII, Ti XVII & Fe XXI which has 69 fine structures by using the fully relativistic flexible atomic code (FAC) program. These data are used in the determination of the reduced population and gain coefficients over a wide range of electron densities from (10<sup>+18</sup> to 10<sup>+23</sup>) and at various plasmas temperatures. The results show that the transitions in Ar<sup>18+</sup>, Ti<sup>22+</sup>, and Fe<sup>26+</sup> ions are the most promising laser emission lines in the XUV and soft X-ray spectral regions.
基金supported by the National Natural Science Foundation of China(62305244,52372003,62374112,62105078)Shandong Province Natural ScienceFoundation(ZR2021QE060,ZR2021QF009)+2 种基金Natural Science Foundation of Heilongjiang Province of China(ZD2023E004)Young Elite Scientists Sponsorship Program by China Association for Science and Technology(2022QNRC001)Youth science and technology innovation team of Shandong Province institution of higher learning(2022KJ258).
文摘Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the formidable requirement of population inversion at short wavelengths.Rare-earth(RE)-activated microcavities,featuring highquality factor(Q)and small mode volume of whispering gallery modes,offer a great opportunity for achieving infrared-to-visible upconversion(UC)lasing.Here,we report that batch-produced nano-glass composite(GC)microspheres incorporating RE-doped fluoride nanocrystals show efficient UC emissions.These multi-phase composite microspheres exhibit a high Q value(≥10^(5)),comparable to that of conventional multi-component glass microspheres.The UC lasing with pure red,green,and blue(RGB)emissions are demonstrated based on a highly efficient tapered fiber-microsphere system.More importantly,the GC microspheres manifest reduced(by 45%)lasing threshold and enhanced(more than four times)slope effciency.These characteristics,together with excellent long-term stability,suggest a promising solution to achieving highly robust,stand-alone,low-threshold,and versatile UC microlasers.
文摘We investigate the dynamics of a system that consists of ultra-cold three-level atoms interacting with radiation fields.We derive the analytical expressions for the population dynamics of the system,particularly,in the presence and absence of nonlinear collisions by considering the rotating wave approximation(RWA).We also reanalyze the dynamics of the system beyond RWA and obtain the state vector of the system to study and compare the time behavior of population inversion.Our results show that the system undergoes two pure quantum phenomena,i.e.,the collapse-revival and macroscopic quantum self-trapping due to nonlinear collisional interactions.The occurrence of such phenomena strongly depends on the number of atoms in the system and also the ratio of interaction strengths in the considered system.Finally,we show that the result of the perturbed time evolution operator up to the second-order is in agreement with the numerical solution of the Schrodinger equation.The results presented in the paper may be useful for the design of devices that produce a coherent beam of bosonic atoms known as an atom laser.
