Control of magnetization plays an important role in the scientific and technological field of manipulating spin systems. In this work, we study the problem of manipulating nuclear magnetization in the spin-exchange op...Control of magnetization plays an important role in the scientific and technological field of manipulating spin systems. In this work, we study the problem of manipulating nuclear magnetization in the spin-exchange optical pumping system, including accelerating the recovery of nuclear polarization and fixing it on a specific desired state. A real-time feedback control strategy is exploited here. We have also done some numerical simulations, with the results clearly demonstrating the effectiveness of our method, that the nuclear magnetization is able to be driven towards the equilibrium state at a much faster speed and also can be stabilized to a target state. We expect that our feedback control method can find applications in gyro experiments.展开更多
Using the Keldysh-Green function,we present a theoretical study on the electron transport properties of two coupled quantum dots under optical pumping. Plateaus in the I-V curve and resonant peaks in the transmission ...Using the Keldysh-Green function,we present a theoretical study on the electron transport properties of two coupled quantum dots under optical pumping. Plateaus in the I-V curve and resonant peaks in the transmission coefficient occur and can be explained by the local electron density of states in the quantum dots. The effects of the optical pumping frequency and intensity on the transport properties of the system are also discussed. The electron dynamical localization phenomenon occurs when the optical pumping frequency is equal to the discrete hole energy level. This result can be used to realize optical control switches.展开更多
Dynamically tunable laser sources are highly promising for realizing visionary concepts of integrated photonic circuits and other applications. In this paper, a Ga N-based laser with an integrated PN junction heater o...Dynamically tunable laser sources are highly promising for realizing visionary concepts of integrated photonic circuits and other applications. In this paper, a Ga N-based laser with an integrated PN junction heater on Si is fabricated.The photoluminescence properties of the Ga N beam cavity are controlled by temperature, and the Joule heater provides electrically driven regulation of temperature. These two features of the cavity make it possible to realize convenient tuning of the lasing properties. The multi-functional Ga N beam cavity achieves optically pumped lasing with a single mode near 362.4 nm with a high Q-factor of 1394. The temperature of this device increases by 0–5℃ under the Joule heating effect. Then, electrical control of the lasing mode is demonstrated. The lasing resonant peak shows a continuous redshift of about 0.5 nm and the device also exhibits dynamic switching of its lasing mode. The lasing modulation can be ascribed to temperature-induced reduction of the bandgap. Our work may be of benefit for external optical modulation in future chip-based optoelectronic devices.展开更多
The momentum relaxation time of a photoexcited graphene in the THz frequency range has been studied by using terabertz time domain spectroscopy under optical pumping at room temperature. It is found that the momentum ...The momentum relaxation time of a photoexcited graphene in the THz frequency range has been studied by using terabertz time domain spectroscopy under optical pumping at room temperature. It is found that the momentum relaxation time of the graphene as a function of the optical pumping intensity exhibits a threshold behavior. The features of the momentum relaxation time as a function of the optical pumping intensity are also investigated. The results are useful for understanding the basic underlying physics of graphene scattering as well as finding the possible applications in carbon- based electronics.展开更多
A new pumping-probing scheme for the optically pumped cesium beam frequency standard has been experimentally tested in our laboratory.The stability of the optically pumped cesium beam frequency standard was measured b...A new pumping-probing scheme for the optically pumped cesium beam frequency standard has been experimentally tested in our laboratory.The stability of the optically pumped cesium beam frequency standard was measured by comparing its 10 MHz output with an HP5071A commercial cesium atomic clock.The result shows that the frequency stability for the 1 s and 30000s sample times are 1.2×10^(-11) and 3.7×10^(-13),respectively.It was proved that the new pumping scheme works well.展开更多
A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an import...A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an important factor that limits the long-term frequency stability. We minimize the drift of the light angle by using a fiber- coupled output, and lock the frequency of a distributed-feedback diode laser to the fluorescence spectrum of the atomic beam. The measured frequency stability is about 3.5 ×10^-11 at i s and reaches 1.5 × 10^-12 at 2000s. The Allan variance keeps going down for up to thousands of seconds, indicating that the medium- and long-term stability of the laser frequency is significantly improved and perfectly fulfills the requirement for the optical pumping cesium clock.展开更多
Requested by the authors, the article entitled "Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis", published in Chinese Physics B, 2017, Vol. 26, Issue 9, Artic...Requested by the authors, the article entitled "Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis", published in Chinese Physics B, 2017, Vol. 26, Issue 9, Article No. 093301, has been withdrawn from the publication. The authors found that the axes in the rotating frame xy'z are not all time-invariant, so Eq. (12) obtained from Eq. (11) is incorrect, and the conclusion is inaccurate.展开更多
We present an investigation of double-resonance optical pumping (DROP) spectra under the condition of single-photon frequency detuning based on a cesium 6S1/2-6P3/2-8S1/2 ladder-type system with a room-temperature v...We present an investigation of double-resonance optical pumping (DROP) spectra under the condition of single-photon frequency detuning based on a cesium 6S1/2-6P3/2-8S1/2 ladder-type system with a room-temperature vapor cell. Two DROP peaks are found, and their origins are explored. One peak has a narrow linewidth due to the atomic coherence for a counterpropagating configuration; the other peak has a broad linewidth, owing to the spontaneous decay for a coprop-agating configuration. This kind of off-resonant DROP spectrum can be used to control and offset-lock a laser frequency to a transition between excited states. We apply this technique to a multiphoton cesium magneto-optical trap, which can efficiently trap atoms on both red and blue sides of the two-photon resonance.展开更多
In a Doppler-broadened ladder-type cesium atomic system (6S1/2 6P3/2-8S1/2), this paper characterizes electro- magnetically induced transparency (EIT) in two different experimental arrangements, and investigates t...In a Doppler-broadened ladder-type cesium atomic system (6S1/2 6P3/2-8S1/2), this paper characterizes electro- magnetically induced transparency (EIT) in two different experimental arrangements, and investigates the influence of the double-resonance optical-pumping (DROP) effect on EIT in both arrangements. When the probe laser is weak, DROP is explicitly suppressed. When the probe laser is moderate, population of the intermediate level (6P3/2 FI = 5) is remarkable, therefore DROP is mixed with EIT. An interesting bimodal spectrum with the broad component due to DROP and the narrow part due to EIT has been clearly observed in cesium 6S1/2 F = 4-6P3/2 F^1= 5-8S1/2 F^11 = 4 transitions.展开更多
The solution of the time-dependent periodic pumping non-degenerate optical parametric amplifier (NOPA) is derived when the pump depletion is considered both above and below thresholds. Based on this solution, the qu...The solution of the time-dependent periodic pumping non-degenerate optical parametric amplifier (NOPA) is derived when the pump depletion is considered both above and below thresholds. Based on this solution, the quantum fluctuation calculated shows that a high entanglement and a good squeezing degree of the parametric light beams are achieved near and above thresholds. We adopt two kinds of pump fields: (i) a continuously modulated pump with a sinusoidal envelope; (ii) a sequence of laser pulses with Gaussian envelopes. We analyse the time evolution of continuous variable entanglement by analytical and numerical calculations, and show that the periodic driven pumping also improves the degree of entanglement. The squeezing and Einstein-Podolsky-Rosen (EPR) entanglement by using the two pumping driven functions are investigated from below to above the threshold regions, the tendencies are nearly the same, and the Caussian driven function is superior to that of the sine driven function, when the maximum squeezing and the minimum variance of quantum fluctuation are considered. In the meantime, the generalization of frequency degenerate OPA to frequency non-degenerated OPA problem is investigated.展开更多
Nuclear-spin states of gaseous-state Cs atoms in the ground state are optically manipulated using a Ti:sapphire laser in a magnetic field of 1.516 T, in which optical coupling of the nuclear-spin states is achieved t...Nuclear-spin states of gaseous-state Cs atoms in the ground state are optically manipulated using a Ti:sapphire laser in a magnetic field of 1.516 T, in which optical coupling of the nuclear-spin states is achieved through hyperfine interactions between electrons and nuclei. The steady-state population distribution in the hyperfine Zeeman sublevels of the ground state is detected by using a tunable diode laser. Furthermore, the state population transfer among the hyperfine Zeeman sublevels, which results from the collision-induced modification δa(S·I) of the hyperfine interaction of Cs in the ground state due to stochastic collisions between Cs atoms and buffer-gas molecules, is studied at different buffer-gas pressures. The experimental results show that high-field optical pumping and the small change δa(S · I) of the hyperfine interaction can strongly cause the state population transfer and spin-state interchange among the hyperfine Zeeman sublevels. The calculated results maybe explain the steady-state population in hyperfine Zeeman sublevels in terms of rates of optical-pumping, electron-spin flip, nuclear spin flip, and electron-nuclear spin flip-flop transitions among the hyperfine Zeeman sublevels of the ground state of Cs atoms. This method may be applied to the nuclear-spin-based solid-state quantum computation.展开更多
A magneto-optical trap (MOT) for cesium atoms that operates without a separate repumping laser is reported. The differences between a normal MOT and this kind of MOT have been experimentally studied. The influences of...A magneto-optical trap (MOT) for cesium atoms that operates without a separate repumping laser is reported. The differences between a normal MOT and this kind of MOT have been experimentally studied. The influences of a repumping laser on cooling and trapping cesium atoms in the MOT have been carefully investigated. The results reveal that it is the critical injection-locked state of the diode laser that makes magneto-optical trapping of cesium atoms possible without a separate repumping laser.展开更多
We propose and realize a new optical state selection method on a cesium atomic fountain clock by applying a two-laser 3-3'optical pumping configuration to spin polarize atoms.The atoms are prepared in|F=3,mF=0>...We propose and realize a new optical state selection method on a cesium atomic fountain clock by applying a two-laser 3-3'optical pumping configuration to spin polarize atoms.The atoms are prepared in|F=3,mF=0>clock state with optical pumping directly after being launched up,followed by a pushing beam to push away the atoms remaining in the|F=4>state.With a state selection efficiency exceeding 92%,this optical method can substitute the traditional microwave state selection,and helps to develop a more compact physical package.A Ramsey fringe has been achieved with this optical state selection method,and a contrast of 90%is obtained with a full width half maximum of 0.92 Hz.The short-term frequency stability of 6.8×10^(-14)(τ/s)^(-1/2) is acquired.In addition,the number of detected atoms is increased by a factor of 1.7 with the optical state selection.展开更多
Sub-natural linewidth optical-pumping dips have been observed in a homogeneously broadened. fluorescence line in Na atomic beam spectroscopy. To our knowledge, this is the first observation of sub-natural linewidth di...Sub-natural linewidth optical-pumping dips have been observed in a homogeneously broadened. fluorescence line in Na atomic beam spectroscopy. To our knowledge, this is the first observation of sub-natural linewidth dip by optical pumping. A theoretic explanation is given.展开更多
To improve the signal to noise ratio(SNR)and the short-term stability of cesium atomic fountain clocks,the work of two-laser optical pumping is presented theoretically and experimentally.The short-term stability of th...To improve the signal to noise ratio(SNR)and the short-term stability of cesium atomic fountain clocks,the work of two-laser optical pumping is presented theoretically and experimentally.The short-term stability of the NIM6 fountain clock has been improved by preparing more cold atoms in the|F=4,m_(F)=0>clock state with a shortened cycle time.Two π-polarized laser beams overlapped in the horizontal plane have been applied after launching,one is resonant with|F=4>→|F′=4>transition and the other is resonant with|F=3>→|F′=4>transition.With optical pumping,the population accumulated in the|m_(F)=0>clock state is improved from 11%to 63%,and the detection signal is increased by a factor of 4.2,the SNR of the clock transition probability and the short-term stability are also improved accordingly.展开更多
A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and ...A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and theoretical calculation is conducted to analyze this model. We demonstrate that when the optical pumping nuclear magnetic resonance system rotates in a plane parallel to the quantization axis, it will maintain a steady state with respect to the quantization axis which is independent of rotational speed and direction.展开更多
Double resonance optical pumping spectroscopy has an outstanding advantage of high signal-to-noise ratio, thus having potential applications in precision measurement. With the counter propagated 780nm and 776nm laser ...Double resonance optical pumping spectroscopy has an outstanding advantage of high signal-to-noise ratio, thus having potential applications in precision measurement. With the counter propagated 780nm and 776nm laser beams acting on a rubidium vapor cell, the high resolution spectrum of 5S1/2 - 5P3/2 - 5D5/2 ladder-type transition of ST Rb atoms is obtained by monitoring the population of the 5S1/2 ground state. The dependence of the spectroscopy lineshape on the probe and coupling fields are comprehensively studied in theory and experiment. This research is helpful for measurement of fundamental physical constants by high resolution spectroscopy.展开更多
We implement optical pumping to prepare cold atoms in our prototype of the ST Rb space cold atom clock, which operates in the one-way mode. Several modifications are made on our previous physical and optical system. T...We implement optical pumping to prepare cold atoms in our prototype of the ST Rb space cold atom clock, which operates in the one-way mode. Several modifications are made on our previous physical and optical system. The effective atomic signal in the top detection zone is increased to 2.5 times with 87% pumping efficiency. The temperature of the cold atom cloud is increased by 1.4 μK. We study the dependences of the effective signal gain and pumping efficiency on the pumping laser intensity and detuning. The effects of σ transition are discussed. This technique may be used in the future space cold atom clocks.展开更多
Vector beams with spiral phase and spatially varying polarization profiles have many applications from optical micromanipulation to materials processing. Here, we propose and demonstrate an atomic spatial mode extract...Vector beams with spiral phase and spatially varying polarization profiles have many applications from optical micromanipulation to materials processing. Here, we propose and demonstrate an atomic spatial mode extracting scheme for the vector beam based on polarization-dependent absorption in the atom vapor. By employing the linear polarization pump beam which induces polarization sensitive absorption in the atomic ensemble, a counter-propagated weak probe vector beam is extracted by spatial absorption, and extracted part still maintains the original polarization and the vortex phase.The topological charges of the extracted mode are verified by interfering with the Gaussian beam, and it can be found that the orbital angular momentum is conserved in the extracting process. Our work will have potential applications in non-destructive spatial mode identification, and is also useful for studying higher-dimensional quantum information based on atomic ensembles.展开更多
Magnetocardiography(MCG)measurement is important for investigating the cardiac biological activities.Traditionally,the extremely weak MCG signal was detected by using superconducting quantum interference devices(SQUID...Magnetocardiography(MCG)measurement is important for investigating the cardiac biological activities.Traditionally,the extremely weak MCG signal was detected by using superconducting quantum interference devices(SQUIDs).As a room-temperature magnetic-field sensor,optically pumped magnetometer(OPM)has shown to have comparable sensitivity to that of SQUIDs,which is very suitable for biomagnetic measurements.In this paper,a synthetic gradiometer was constructed by using two OPMs under spin-exchange relaxation-free(SERF)conditions within a moderate magnetically shielded room(MSR).The magnetic noise of the OPM was measured to less than 70 fT/Hz1/2.Under a baseline of 100 mm,noise cancellation of about 30 dB was achieved.MCG was successfully measured with a signal to noise ratio(SNR)of about 37 dB.The synthetic gradiometer technique was very effective to suppress the residual environmental fields,demonstrating the OPM gradiometer technique for highly cost-effective biomagnetic measurements.展开更多
基金supported by the National Key Basic Research Program of China(Grant Nos.2014CB848700,and 2013CB921800)
文摘Control of magnetization plays an important role in the scientific and technological field of manipulating spin systems. In this work, we study the problem of manipulating nuclear magnetization in the spin-exchange optical pumping system, including accelerating the recovery of nuclear polarization and fixing it on a specific desired state. A real-time feedback control strategy is exploited here. We have also done some numerical simulations, with the results clearly demonstrating the effectiveness of our method, that the nuclear magnetization is able to be driven towards the equilibrium state at a much faster speed and also can be stabilized to a target state. We expect that our feedback control method can find applications in gyro experiments.
文摘Using the Keldysh-Green function,we present a theoretical study on the electron transport properties of two coupled quantum dots under optical pumping. Plateaus in the I-V curve and resonant peaks in the transmission coefficient occur and can be explained by the local electron density of states in the quantum dots. The effects of the optical pumping frequency and intensity on the transport properties of the system are also discussed. The electron dynamical localization phenomenon occurs when the optical pumping frequency is equal to the discrete hole energy level. This result can be used to realize optical control switches.
基金the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20210593)the Foundation of Jiangsu Provincial Double Innovation Doctor Program (Grant No. 30644)+2 种基金the National Natural Science Foundation of China (Grant No. 62204127)State Key Laboratory of Luminescence and Applications (Grant No. SKLA 202104)open research fund of Key Lab of Broadband Wireless Communication and Sensor Network Technology (Nanjing University of Posts and Telecommunications, Ministry of Education)。
文摘Dynamically tunable laser sources are highly promising for realizing visionary concepts of integrated photonic circuits and other applications. In this paper, a Ga N-based laser with an integrated PN junction heater on Si is fabricated.The photoluminescence properties of the Ga N beam cavity are controlled by temperature, and the Joule heater provides electrically driven regulation of temperature. These two features of the cavity make it possible to realize convenient tuning of the lasing properties. The multi-functional Ga N beam cavity achieves optically pumped lasing with a single mode near 362.4 nm with a high Q-factor of 1394. The temperature of this device increases by 0–5℃ under the Joule heating effect. Then, electrical control of the lasing mode is demonstrated. The lasing resonant peak shows a continuous redshift of about 0.5 nm and the device also exhibits dynamic switching of its lasing mode. The lasing modulation can be ascribed to temperature-induced reduction of the bandgap. Our work may be of benefit for external optical modulation in future chip-based optoelectronic devices.
基金supported by the National Natural Science Foundation of China (Grants Nos. 10974063 and 61177095)the Hubei Natural Science Foundation, China (Grant Nos. 2010CDA001 and 2012FFA074)+2 种基金the Research Foundation of Huazhong University of Science and Technology, China (Grant Nos. 01-09-230904 and 02-16-230008)the PhD Program Foundation of Ministry of Education of China (Grant No. 20100142110042)the Fundamental Research Funds for the Central Universities, China (Grant Nos. HUST: 2010MS041 and 2011TS001)
文摘The momentum relaxation time of a photoexcited graphene in the THz frequency range has been studied by using terabertz time domain spectroscopy under optical pumping at room temperature. It is found that the momentum relaxation time of the graphene as a function of the optical pumping intensity exhibits a threshold behavior. The features of the momentum relaxation time as a function of the optical pumping intensity are also investigated. The results are useful for understanding the basic underlying physics of graphene scattering as well as finding the possible applications in carbon- based electronics.
基金Supported by the National Natural Science Foundation of China under Grant No.69678031the Foundation for University Kay Teacher by the Education Ministry of China。
文摘A new pumping-probing scheme for the optically pumped cesium beam frequency standard has been experimentally tested in our laboratory.The stability of the optically pumped cesium beam frequency standard was measured by comparing its 10 MHz output with an HP5071A commercial cesium atomic clock.The result shows that the frequency stability for the 1 s and 30000s sample times are 1.2×10^(-11) and 3.7×10^(-13),respectively.It was proved that the new pumping scheme works well.
基金Supported by the National Fundamental Research Program of China under Grant No 2011CB921501the National Natural Science Foundation of China under Grant Nos 91336103,10934010 and 61078026
文摘A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an important factor that limits the long-term frequency stability. We minimize the drift of the light angle by using a fiber- coupled output, and lock the frequency of a distributed-feedback diode laser to the fluorescence spectrum of the atomic beam. The measured frequency stability is about 3.5 ×10^-11 at i s and reaches 1.5 × 10^-12 at 2000s. The Allan variance keeps going down for up to thousands of seconds, indicating that the medium- and long-term stability of the laser frequency is significantly improved and perfectly fulfills the requirement for the optical pumping cesium clock.
基金Project supported by the Special Scientific Research Fund of the Meteorological Public Welfare of the Ministry of Sciences and Technology,China(Grant Nos.GYHY201406003 and GYHY201406001) the Opening Foundation of the State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences(Grant Nos.2015LASW-B01 and 2015LASW-A02) the National Natural Science Foundation of China(Grant Nos.41375054,41575064,91437215,and 41405055)
文摘Requested by the authors, the article entitled "Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis", published in Chinese Physics B, 2017, Vol. 26, Issue 9, Article No. 093301, has been withdrawn from the publication. The authors found that the axes in the rotating frame xy'z are not all time-invariant, so Eq. (12) obtained from Eq. (11) is incorrect, and the conclusion is inaccurate.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB921601)the National Natural Science Foundation of China(Grant Nos.11104172,11274213,61205215,and 61227902)+2 种基金the Project for Excellent Research Teams of the National Natural Science Foundation of China(Grant No.61121064)the Research Project for Returned Abroad Scholars from Universities of Shanxi Province,China(Grant No.2012-015)the Program for Science and Technology Star of Taiyuan,Shanxi,China(Grant No.12024707)
文摘We present an investigation of double-resonance optical pumping (DROP) spectra under the condition of single-photon frequency detuning based on a cesium 6S1/2-6P3/2-8S1/2 ladder-type system with a room-temperature vapor cell. Two DROP peaks are found, and their origins are explored. One peak has a narrow linewidth due to the atomic coherence for a counterpropagating configuration; the other peak has a broad linewidth, owing to the spontaneous decay for a coprop-agating configuration. This kind of off-resonant DROP spectrum can be used to control and offset-lock a laser frequency to a transition between excited states. We apply this technique to a multiphoton cesium magneto-optical trap, which can efficiently trap atoms on both red and blue sides of the two-photon resonance.
基金partially supported by the National Natural Science Foundation of China (Grant Nos. 61078051,60978017,10974125 and 60821004)the NCET Project from the Education Ministry of China (Grant No. NCET-07-0524)the Specialized Research Fund for the Doctoral Program of China (Grant No. 20070108003)
文摘In a Doppler-broadened ladder-type cesium atomic system (6S1/2 6P3/2-8S1/2), this paper characterizes electro- magnetically induced transparency (EIT) in two different experimental arrangements, and investigates the influence of the double-resonance optical-pumping (DROP) effect on EIT in both arrangements. When the probe laser is weak, DROP is explicitly suppressed. When the probe laser is moderate, population of the intermediate level (6P3/2 FI = 5) is remarkable, therefore DROP is mixed with EIT. An interesting bimodal spectrum with the broad component due to DROP and the narrow part due to EIT has been clearly observed in cesium 6S1/2 F = 4-6P3/2 F^1= 5-8S1/2 F^11 = 4 transitions.
基金Project supported by the Natural Science Foundation of Shanxi Province, China (Grant No 2006011003)
文摘The solution of the time-dependent periodic pumping non-degenerate optical parametric amplifier (NOPA) is derived when the pump depletion is considered both above and below thresholds. Based on this solution, the quantum fluctuation calculated shows that a high entanglement and a good squeezing degree of the parametric light beams are achieved near and above thresholds. We adopt two kinds of pump fields: (i) a continuously modulated pump with a sinusoidal envelope; (ii) a sequence of laser pulses with Gaussian envelopes. We analyse the time evolution of continuous variable entanglement by analytical and numerical calculations, and show that the periodic driven pumping also improves the degree of entanglement. The squeezing and Einstein-Podolsky-Rosen (EPR) entanglement by using the two pumping driven functions are investigated from below to above the threshold regions, the tendencies are nearly the same, and the Caussian driven function is superior to that of the sine driven function, when the maximum squeezing and the minimum variance of quantum fluctuation are considered. In the meantime, the generalization of frequency degenerate OPA to frequency non-degenerated OPA problem is investigated.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10374103 and 10574143), and the National Basic Research Program of China (Grant No 2001CB309309).
文摘Nuclear-spin states of gaseous-state Cs atoms in the ground state are optically manipulated using a Ti:sapphire laser in a magnetic field of 1.516 T, in which optical coupling of the nuclear-spin states is achieved through hyperfine interactions between electrons and nuclei. The steady-state population distribution in the hyperfine Zeeman sublevels of the ground state is detected by using a tunable diode laser. Furthermore, the state population transfer among the hyperfine Zeeman sublevels, which results from the collision-induced modification δa(S·I) of the hyperfine interaction of Cs in the ground state due to stochastic collisions between Cs atoms and buffer-gas molecules, is studied at different buffer-gas pressures. The experimental results show that high-field optical pumping and the small change δa(S · I) of the hyperfine interaction can strongly cause the state population transfer and spin-state interchange among the hyperfine Zeeman sublevels. The calculated results maybe explain the steady-state population in hyperfine Zeeman sublevels in terms of rates of optical-pumping, electron-spin flip, nuclear spin flip, and electron-nuclear spin flip-flop transitions among the hyperfine Zeeman sublevels of the ground state of Cs atoms. This method may be applied to the nuclear-spin-based solid-state quantum computation.
基金the National Natural Science Foundation of China under Grant No.19704001the Doctoral Program Foundation of the Institute of Higher Education.
文摘A magneto-optical trap (MOT) for cesium atoms that operates without a separate repumping laser is reported. The differences between a normal MOT and this kind of MOT have been experimentally studied. The influences of a repumping laser on cooling and trapping cesium atoms in the MOT have been carefully investigated. The results reveal that it is the critical injection-locked state of the diode laser that makes magneto-optical trapping of cesium atoms possible without a separate repumping laser.
基金Project supported by the National Natural Science Foundation of China(Grant No.11873044).
文摘We propose and realize a new optical state selection method on a cesium atomic fountain clock by applying a two-laser 3-3'optical pumping configuration to spin polarize atoms.The atoms are prepared in|F=3,mF=0>clock state with optical pumping directly after being launched up,followed by a pushing beam to push away the atoms remaining in the|F=4>state.With a state selection efficiency exceeding 92%,this optical method can substitute the traditional microwave state selection,and helps to develop a more compact physical package.A Ramsey fringe has been achieved with this optical state selection method,and a contrast of 90%is obtained with a full width half maximum of 0.92 Hz.The short-term frequency stability of 6.8×10^(-14)(τ/s)^(-1/2) is acquired.In addition,the number of detected atoms is increased by a factor of 1.7 with the optical state selection.
文摘Sub-natural linewidth optical-pumping dips have been observed in a homogeneously broadened. fluorescence line in Na atomic beam spectroscopy. To our knowledge, this is the first observation of sub-natural linewidth dip by optical pumping. A theoretic explanation is given.
基金the National Natural Science Foundation of China(Grant No.11873044).
文摘To improve the signal to noise ratio(SNR)and the short-term stability of cesium atomic fountain clocks,the work of two-laser optical pumping is presented theoretically and experimentally.The short-term stability of the NIM6 fountain clock has been improved by preparing more cold atoms in the|F=4,m_(F)=0>clock state with a shortened cycle time.Two π-polarized laser beams overlapped in the horizontal plane have been applied after launching,one is resonant with|F=4>→|F′=4>transition and the other is resonant with|F=3>→|F′=4>transition.With optical pumping,the population accumulated in the|m_(F)=0>clock state is improved from 11%to 63%,and the detection signal is increased by a factor of 4.2,the SNR of the clock transition probability and the short-term stability are also improved accordingly.
基金Project supported by the National Natural Science Foundation of China(Grant No.61475192)
文摘A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and theoretical calculation is conducted to analyze this model. We demonstrate that when the optical pumping nuclear magnetic resonance system rotates in a plane parallel to the quantization axis, it will maintain a steady state with respect to the quantization axis which is independent of rotational speed and direction.
基金Supported by the National Key R&D Program of China under Grant No 2017YFA0304203the National Natural Science Foundation of China under Grant Nos 61575116,61705122,61728502,91736209 and 11434007+2 种基金the Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China under Grant No IRT13076the Program for Sanjin Scholars of Shanxi Province,the Applied Basic Research Project of Shanxi Province under Grant No 201701D221004the Fund for Shanxi ‘1331 Project’ Key Subjects Construction
文摘Double resonance optical pumping spectroscopy has an outstanding advantage of high signal-to-noise ratio, thus having potential applications in precision measurement. With the counter propagated 780nm and 776nm laser beams acting on a rubidium vapor cell, the high resolution spectrum of 5S1/2 - 5P3/2 - 5D5/2 ladder-type transition of ST Rb atoms is obtained by monitoring the population of the 5S1/2 ground state. The dependence of the spectroscopy lineshape on the probe and coupling fields are comprehensively studied in theory and experiment. This research is helpful for measurement of fundamental physical constants by high resolution spectroscopy.
基金Supported by the Fund from the Ministry of Science and Technology of China under Grant No 2013YQ09094304the Youth Innovation Promotion Association of Chinese Academy of Sciences
文摘We implement optical pumping to prepare cold atoms in our prototype of the ST Rb space cold atom clock, which operates in the one-way mode. Several modifications are made on our previous physical and optical system. The effective atomic signal in the top detection zone is increased to 2.5 times with 87% pumping efficiency. The temperature of the cold atom cloud is increased by 1.4 μK. We study the dependences of the effective signal gain and pumping efficiency on the pumping laser intensity and detuning. The effects of σ transition are discussed. This technique may be used in the future space cold atom clocks.
文摘Vector beams with spiral phase and spatially varying polarization profiles have many applications from optical micromanipulation to materials processing. Here, we propose and demonstrate an atomic spatial mode extracting scheme for the vector beam based on polarization-dependent absorption in the atom vapor. By employing the linear polarization pump beam which induces polarization sensitive absorption in the atomic ensemble, a counter-propagated weak probe vector beam is extracted by spatial absorption, and extracted part still maintains the original polarization and the vortex phase.The topological charges of the extracted mode are verified by interfering with the Gaussian beam, and it can be found that the orbital angular momentum is conserved in the extracting process. Our work will have potential applications in non-destructive spatial mode identification, and is also useful for studying higher-dimensional quantum information based on atomic ensembles.
基金Project supported by the National Natural Science Foundation of China(Grant No.61701486)。
文摘Magnetocardiography(MCG)measurement is important for investigating the cardiac biological activities.Traditionally,the extremely weak MCG signal was detected by using superconducting quantum interference devices(SQUIDs).As a room-temperature magnetic-field sensor,optically pumped magnetometer(OPM)has shown to have comparable sensitivity to that of SQUIDs,which is very suitable for biomagnetic measurements.In this paper,a synthetic gradiometer was constructed by using two OPMs under spin-exchange relaxation-free(SERF)conditions within a moderate magnetically shielded room(MSR).The magnetic noise of the OPM was measured to less than 70 fT/Hz1/2.Under a baseline of 100 mm,noise cancellation of about 30 dB was achieved.MCG was successfully measured with a signal to noise ratio(SNR)of about 37 dB.The synthetic gradiometer technique was very effective to suppress the residual environmental fields,demonstrating the OPM gradiometer technique for highly cost-effective biomagnetic measurements.