A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase...A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase to sine mapping data is compressed using sine symmetry technique, sine-phase difference technique, quad line approximation technique,and quantization and error read only memory （QE-ROM） technique. The ROM size is reduced by 98% using these techniques. A compact DDFS chip with 32bit phase storage depth and a 10bit on-chip digital to analog converter has been successfully implemented using a standard 0.35μm CMOS process. The core area of the DDFS is 1.6mm^2. It consumes 167mW at 3.3V,and its spurious free dynamic range is 61dB.展开更多
A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequenc...A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.展开更多
We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experime...We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg＋ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg＋ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.展开更多
We report construction of an iodine-stabilized laser frequency standard at 532 nm based on modulation transfer spectroscopy(MTS)technology with good reproducibility.A frequency stability of 2.5×10^(-14)at 1 s ave...We report construction of an iodine-stabilized laser frequency standard at 532 nm based on modulation transfer spectroscopy(MTS)technology with good reproducibility.A frequency stability of 2.5×10^(-14)at 1 s averaging time is achieved,and the frequency reproducibility has a relative uncertainty of 3.5×10^(-13),demonstrating the great stability of our setup.The systematic uncertainty of the iodine-stabilized laser frequency standard is evaluated,especially the contribution of the residual amplitude modulation(RAM).The contribution of the RAM in MTS cannot be evaluated directly.To solve this problem,we theoretically deduce the MTS signal with RAM under large modulation depth,and prove that the non-symmetric shape of the MTS signal is directly related to the MTS effect.The non-symmetric shape factor can be calibrated with a frequency comb,and in real experiments,this value can be obtained by least-squares fitting of the MTS signal,from which we can infer the RAMinduced frequency shift.The full frequency uncertainty is evaluated to be 5.3 kHz(corresponding to a relative frequency uncertainty of 9.4×10^(-12)).The corrected transition frequency has a difference from the BIPM-recommended value of 2 kHz,which is within 1σ uncertainty,proving the validity of our evaluation.展开更多
We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity la...We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127℃ Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a ≈ 40 for 1359nm and 1470nm lasers. The 147Ohm laser linewidth is measured to be 407.3Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.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
This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The st...This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The stability and drift rate of the frequency standard are calculated using 1-year monitoring data.The UTC-NIM Disciplined Oscillator(NIMDO)system improves the system time accuracy and stability to the level of 5 ns.Pulsar timing observations were carried out for several months.The weighted RMS of timing residuals reaches the level of less than 3.0μs.展开更多
In this paper, we analyze and design a new type of servo system with noninteger voltage controlled crystal oscillator （VCXO） for rubidium atomic frequency standard （RAFS）, which does not require fractional frequen...In this paper, we analyze and design a new type of servo system with noninteger voltage controlled crystal oscillator （VCXO） for rubidium atomic frequency standard （RAFS）, which does not require fractional frequency synthesizer. By the estab- lishment of the loop equations with noises and drifts, we prove that all the components of the loop can affect its performance in- dex, and in which, RAFS long-term frequency stability is mainly determined by frequency multiplier, quantum system, and servo amplifier; the short-term one is mostly decided by VCXO. Owing to the elimination of the frequency synthesizer and its additive mixing unit, we can reduce phase noise and stray of the servo sys- tem, and it is favorable for miniaturizing the RAFS system. In addition, we adopt some targeted optimization measures to im- prove the frequency stability index. The good short-term fre- quency stability index is also validated by the test results.展开更多
We report a 42Ohm external cavity diode laser with an interference filter （IF） of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye refle...We report a 42Ohm external cavity diode laser with an interference filter （IF） of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye reflector are used for selecting wavelength and light feedback, respectively. The measured laser linewidth is 24 kHz when the diode laser is free running. Using this narrow-linewidth IF blue diode laser, we realize a compact Rb optical frequency standard without a complicated PDH system. The preliminary stability of the Rb optical frequency standard is 2 × 10^-13 at I s and decreases to 1.9 ×10^-14 at 1000s. The narrow-linewidth characteristic makes the IF blue diode laser a well suited candidate for the compact Rb optical frequency standard.展开更多
Frequencies of frequency standards are shifted by the local static gravity red shifts and also modulated by the tidal relativistic red shifts. We compute the tidal relativistic red shifts using a time-domain method an...Frequencies of frequency standards are shifted by the local static gravity red shifts and also modulated by the tidal relativistic red shifts. We compute the tidal relativistic red shifts using a time-domain method and present the numerical results for the National Institute of Metrology （NIM） in Beijing, Laboratoire National de Metrologie et Essais-Systeme de References Temps-Espaee （LNE-SYRTE） in Paris and Physikalisch-Teehnische Bundesanstalt （PTB） in Braunschweig. The differences of the tidal relativistic red shift approach as large as 1.1 × 10^-16 when frequency standards at NIM are compared with those at SYRTE and PTB. Moreover, the tidal relativistic red shifts of frequency standards in space stations are also computed.展开更多
The Dick effect is one of the main limits to the frequency stability of a passive frequency standard, especially for the fountain clock and ion dock operated in pulsed mode which require unavoidable dead time during i...The Dick effect is one of the main limits to the frequency stability of a passive frequency standard, especially for the fountain clock and ion dock operated in pulsed mode which require unavoidable dead time during interrogation. Here we measure the phase noise of the interrogation oscillator applied in the microwave frequency standard based on laser-cooled 113^Cd＋ ions, and analyze the Allan deviation limited by the Dick effect. The results indicate that the Dick effect is one of the key issues for the cadmium ion dock to reach expected frequency stability. This problem can be resolved by interrogating the local oscillator continuously with two ion traps.展开更多
Atomic clocks represent the most advanced instruments for providing time-frequency standards,with increasing demand for designs that offer high frequency stability while minimizing size.Central to an atomic clock'...Atomic clocks represent the most advanced instruments for providing time-frequency standards,with increasing demand for designs that offer high frequency stability while minimizing size.Central to an atomic clock's function is the atomic vapor cell,which serves as the quantum reference.Compared to traditional cells,wafer-level micro-electro-mechanical systems(MEMS)vapor cells enable cost-effective,scalable production and facilitate integration with silicon-based chips.In this work,we present a wafer-level MEMS vapor cell featuring an innovative silicon-glass-silicon transverse optical path structure.A single wafer is used to fabricate 24 identical atomic vapor cells,each with precise dimensions of 14 mm×14 mm×4.3 mm,ensuring scalability.We demonstrate an optical frequency standard that combines modulation transfer spectroscopy(MTS)with a MEMS vapor cell,featuring a compact design with excellent performance.This frequency standard achieves stability over averaging times of 1–400 s,with short-term stability of 2.6×10^(-13)at 1 s and 5.1×10^(-14)at 200 s.The laser linewidth is only 3.9 kHz,marking a substantial improvement over existing thermal standards,and opening potential applications in navigation,radar,and precision measurement.This work provides a crucial step toward the development of chip-scale optical clocks.展开更多
We demonstrate a dual-wavelength optical frequency standard based on the dual-optical-transition modulation transfer spectroscopy(DOT-MTS)between different quantum transitions of the rubidium D1(795 nm)and D2(780 nm)l...We demonstrate a dual-wavelength optical frequency standard based on the dual-optical-transition modulation transfer spectroscopy(DOT-MTS)between different quantum transitions of the rubidium D1(795 nm)and D2(780 nm)lines.In a single rubidium atomic ensemble,modulation frequency sidebands from the 780 nm pump beam are simultaneously transferred to both the 780 and 795 nm probe lasers.The DOT-MTS enables the simultaneous stabilization of 780 and 795 nm lasers on a single vapor cell.Both lasers exhibit a frequency instability in the low 10-14range at 1 s of averaging,as estimated from the residual error signal.A theoretical model is developed based on the V-type atomic level structure to illustrate the dual-wavelength spectroscopy.This approach can be extended to develop a multi-wavelength optical frequency standard within a single atomic ensemble,broadening its applicability in fields such as precision metrology,Rydberg atoms,wavelength standards,optical networks,and beyond.展开更多
The transportable optical clock can be deployed in various transportation vehicles,including aviation,aerospace,maritime,and land-based vehicles;provides remote time standards for geophysical monitoring and distribute...The transportable optical clock can be deployed in various transportation vehicles,including aviation,aerospace,maritime,and land-based vehicles;provides remote time standards for geophysical monitoring and distributed coherent sensing;and promotes the unmanned and lightweight development of global time network synchronization.However,the current transportable version of laboratory optical clocks is still limited by factors such as environmental sensitivity,manual maintenance requirements,and high cost.Here we report a single-person portable optical frequency standard using the recently proposed atomic-filter-based laser“Voigt laser”as the local oscillator.It is worth mentioning that due to the inherent characteristics of Voigt lasers,the Voigt optical frequency standard can maintain turn-key functionality under harsh environmental impacts without any manual maintenance requirement.In our experiment,conducted over a duration of 12 min,we subjected the laser diode to multiple temperature shocks,resulting in a cumulative temperature fluctuation of 15℃.Following each temperature shock event,the Voigt optical frequency standard automatically relocked and restored the frequency output.Therefore,this demonstration marks a significant technological breakthrough in automatic quantum devices and might herald the arrival of fully automated time network systems.展开更多
This study investigates the application of miniature quantum references within small-scale optical atomic frequency standards,utilizing a diminutive^(87)Rb glass cell,dimensions of 6 mm×6 mm×6 mm,to establis...This study investigates the application of miniature quantum references within small-scale optical atomic frequency standards,utilizing a diminutive^(87)Rb glass cell,dimensions of 6 mm×6 mm×6 mm,to establish a quantum frequency standard.'By employing the transition spectrum from 5^(2)S_(1/2)F=2 to 5^(2)P_(3/2)F=3,this study successfully demonstrates the development of a compact rubidium atomic optical frequency standard via modulation transfer spectroscopy(MTS).Subsequent to frequency stabilization,the 780 nm clock laser exhibits a linewidth of 6.9 k Hz,and its out-of-loop short-term stability reaches4.1×10^(-13)@1 s,as confirmed through beat frequency analysis.This research not only provides a practical blueprint for the development of small optical atomic frequency standards but also lays down essential groundwork for future advancements in chip-level optical frequency standard technologies.展开更多
A compact extended cavity diode laser （ECDL） system operating at 852 nm for small optically pumped cesium （Cs） beam frequency standards was reported. ECDL and a saturated absorption spectroscopy setup were all bui...A compact extended cavity diode laser （ECDL） system operating at 852 nm for small optically pumped cesium （Cs） beam frequency standards was reported. ECDL and a saturated absorption spectroscopy setup were all built in an aluminum box with dimension of 10 × 10 × 7 （cm）. ECDL was based on a Littman-Metcaff configuration, whose free-running linewidth was less than 600 kHz. A digital automatic frequency lock unit （AFLU） was developed to lock the laser frequency to specify Cs absorption lines automatically and re-lock it in case of lock broken. With AFLU, the laser frequency was continuously locked for several weeks.展开更多
Calcium is one prospective element for the modern optical frequency standard. The 423-nm transition line of calcium atoms has been widely used in laser slowing and laser cooling, the precise spectrum measurement, and ...Calcium is one prospective element for the modern optical frequency standard. The 423-nm transition line of calcium atoms has been widely used in laser slowing and laser cooling, the precise spectrum measurement, and the magnetic optical trapping （MOT）. However, there is no any available commercial diode laser working at this wavelength. We built a 423-nm laser based on extra bow-tie cavity and by using a Brewstercut uncoated BIBO （BiB306） crystal, which worked at room temperature, with conversion efficiency of 3.75%, and a potential up to 20%.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
This paper reports that two identical external-cavity-diode-laser （ECDL） based spectrometers are constructed at 634nm referencing on the hyperfine B-X transition R（80）8-4 of 127I2. The lasers are stabilized on the...This paper reports that two identical external-cavity-diode-laser （ECDL） based spectrometers are constructed at 634nm referencing on the hyperfine B-X transition R（80）8-4 of 127I2. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8 × 10^-12 （after 1000 s） by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.展开更多
Ultra-stable optical cavities are widely used for laser frequency stabilization. In these experiments the laser performance relies on the length stability of the Fabry-Perot cavities. Vibration-induced deformation is ...Ultra-stable optical cavities are widely used for laser frequency stabilization. In these experiments the laser performance relies on the length stability of the Fabry-Perot cavities. Vibration-induced deformation is one of the dominant factors that affect the stability of ultra-stable optical cavities. We have quantitatively analysed the elastic deformation of Fabry-Perot cavities with various shapes and mounting configurations. Our numerical result facilitates a novel approach for the design of ultra-stable cavities that are insensitive to vibrational perturbations. This approach can be applied to many experiments such as laser frequency stabilization, high-precision laser spectroscopy, and optical frequency standards.展开更多
文摘A compact direct digital frequency synthesizer （DDFS） for system-on-chip implementation of the high precision rubidium atomic frequency standard is developed. For small chip size and low power consumption, the phase to sine mapping data is compressed using sine symmetry technique, sine-phase difference technique, quad line approximation technique,and quantization and error read only memory （QE-ROM） technique. The ROM size is reduced by 98% using these techniques. A compact DDFS chip with 32bit phase storage depth and a 10bit on-chip digital to analog converter has been successfully implemented using a standard 0.35μm CMOS process. The core area of the DDFS is 1.6mm^2. It consumes 167mW at 3.3V,and its spurious free dynamic range is 61dB.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91436103 and 11204374
文摘A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11074282 and 11474320
文摘We propose a method to determine the optimal power of the microwave resonance transition that simultaneously improves the signal-to-noise ratio and reduces line width based on saturation broadening theory and experiment. Saturation broadening spectra of the ground state hyperfine transition of trapped 199Hg＋ ions are measured and analyzed. The value of the optimal microwave power is obtained by using the proposed method and is verified. Rabi oscillations decay spectra of trapped 199Hg＋ ions are observed and the optimal microwave irradiation time for the maximum transition signal intensity is determined. This work will help to improve the short-term frequency stability of the mercury ion microwave frequency standard.
基金the National Key Research and Development Program of China(Grant No.2017YFA0304401)Key-Area Research and Development Program of GuangDong Province,China(Grant No.2019B030330001)the National Natural Science Foundation of China(Grant Nos.11174095,61875065,91536116,and 11804108).
文摘We report construction of an iodine-stabilized laser frequency standard at 532 nm based on modulation transfer spectroscopy(MTS)technology with good reproducibility.A frequency stability of 2.5×10^(-14)at 1 s averaging time is achieved,and the frequency reproducibility has a relative uncertainty of 3.5×10^(-13),demonstrating the great stability of our setup.The systematic uncertainty of the iodine-stabilized laser frequency standard is evaluated,especially the contribution of the residual amplitude modulation(RAM).The contribution of the RAM in MTS cannot be evaluated directly.To solve this problem,we theoretically deduce the MTS signal with RAM under large modulation depth,and prove that the non-symmetric shape of the MTS signal is directly related to the MTS effect.The non-symmetric shape factor can be calibrated with a frequency comb,and in real experiments,this value can be obtained by least-squares fitting of the MTS signal,from which we can infer the RAMinduced frequency shift.The full frequency uncertainty is evaluated to be 5.3 kHz(corresponding to a relative frequency uncertainty of 9.4×10^(-12)).The corrected transition frequency has a difference from the BIPM-recommended value of 2 kHz,which is within 1σ uncertainty,proving the validity of our evaluation.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10874009,11074011 and 91436210the International Science and Technology Cooperation Program of China under Grant No 2010DFR10900
文摘We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127℃ Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a ≈ 40 for 1359nm and 1470nm lasers. The 147Ohm laser linewidth is measured to be 407.3Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.
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supported by the Joint Research Fund in Astronomy(Grant Nos.U1931129,U1631115 and U1831117)under cooperative agreement between NSFC and Chinese Academy of Sciences(CAS)NSFC-STINT Grant 11611130023(CH2015-6360)the National Natural Science Foundation of China(NSFC,Grant No.11403054)
文摘This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope(FAST),including the system design,stability measurements and pulsar timing observations.The stability and drift rate of the frequency standard are calculated using 1-year monitoring data.The UTC-NIM Disciplined Oscillator(NIMDO)system improves the system time accuracy and stability to the level of 5 ns.Pulsar timing observations were carried out for several months.The weighted RMS of timing residuals reaches the level of less than 3.0μs.
文摘In this paper, we analyze and design a new type of servo system with noninteger voltage controlled crystal oscillator （VCXO） for rubidium atomic frequency standard （RAFS）, which does not require fractional frequency synthesizer. By the estab- lishment of the loop equations with noises and drifts, we prove that all the components of the loop can affect its performance in- dex, and in which, RAFS long-term frequency stability is mainly determined by frequency multiplier, quantum system, and servo amplifier; the short-term one is mostly decided by VCXO. Owing to the elimination of the frequency synthesizer and its additive mixing unit, we can reduce phase noise and stray of the servo sys- tem, and it is favorable for miniaturizing the RAFS system. In addition, we adopt some targeted optimization measures to im- prove the frequency stability index. The good short-term fre- quency stability index is also validated by the test results.
基金Supported by the China Academy of Space Technology Foundation under Grant No CAST-2015-5-10the National Hi-Tech Research and Development Programthe National Natural Science Foundation of China under Grant No 91436210
文摘We report a 42Ohm external cavity diode laser with an interference filter （IF） of 0.5am narrow-bandwidth and 79% high transmission, which is first used for Rb optical frequency standard. The IF and the cat-eye reflector are used for selecting wavelength and light feedback, respectively. The measured laser linewidth is 24 kHz when the diode laser is free running. Using this narrow-linewidth IF blue diode laser, we realize a compact Rb optical frequency standard without a complicated PDH system. The preliminary stability of the Rb optical frequency standard is 2 × 10^-13 at I s and decreases to 1.9 ×10^-14 at 1000s. The narrow-linewidth characteristic makes the IF blue diode laser a well suited candidate for the compact Rb optical frequency standard.
基金Supported by the National Key R&D Program of China under Grant No 2016YFF0200200
文摘Frequencies of frequency standards are shifted by the local static gravity red shifts and also modulated by the tidal relativistic red shifts. We compute the tidal relativistic red shifts using a time-domain method and present the numerical results for the National Institute of Metrology （NIM） in Beijing, Laboratoire National de Metrologie et Essais-Systeme de References Temps-Espaee （LNE-SYRTE） in Paris and Physikalisch-Teehnische Bundesanstalt （PTB） in Braunschweig. The differences of the tidal relativistic red shift approach as large as 1.1 × 10^-16 when frequency standards at NIM are compared with those at SYRTE and PTB. Moreover, the tidal relativistic red shifts of frequency standards in space stations are also computed.
基金Supported by the Young Scientists Fund of the National Natural Science Foundation of China under Grant No 11304177the National Basic Research Program of China under Grant No 2010CB922901
文摘The Dick effect is one of the main limits to the frequency stability of a passive frequency standard, especially for the fountain clock and ion dock operated in pulsed mode which require unavoidable dead time during interrogation. Here we measure the phase noise of the interrogation oscillator applied in the microwave frequency standard based on laser-cooled 113^Cd＋ ions, and analyze the Allan deviation limited by the Dick effect. The results indicate that the Dick effect is one of the key issues for the cadmium ion dock to reach expected frequency stability. This problem can be resolved by interrogating the local oscillator continuously with two ion traps.
基金Beijing Nova Program(20240484696)INNOVATION Program for Quantum Science and Technology(2021ZD0303202)+1 种基金Wenzhou Major Science and Technology Innovation Key Project(ZG2020046)National Natural Science Foundation of China(62401019)。
文摘Atomic clocks represent the most advanced instruments for providing time-frequency standards,with increasing demand for designs that offer high frequency stability while minimizing size.Central to an atomic clock's function is the atomic vapor cell,which serves as the quantum reference.Compared to traditional cells,wafer-level micro-electro-mechanical systems(MEMS)vapor cells enable cost-effective,scalable production and facilitate integration with silicon-based chips.In this work,we present a wafer-level MEMS vapor cell featuring an innovative silicon-glass-silicon transverse optical path structure.A single wafer is used to fabricate 24 identical atomic vapor cells,each with precise dimensions of 14 mm×14 mm×4.3 mm,ensuring scalability.We demonstrate an optical frequency standard that combines modulation transfer spectroscopy(MTS)with a MEMS vapor cell,featuring a compact design with excellent performance.This frequency standard achieves stability over averaging times of 1–400 s,with short-term stability of 2.6×10^(-13)at 1 s and 5.1×10^(-14)at 200 s.The laser linewidth is only 3.9 kHz,marking a substantial improvement over existing thermal standards,and opening potential applications in navigation,radar,and precision measurement.This work provides a crucial step toward the development of chip-scale optical clocks.
基金Beijing Nova Program(20240484696)Innovation Program for Quantum Science and Technology(2021ZD0303202)Wenzhou Major Science and Technology Innovation Key Project(ZG2020046)。
文摘We demonstrate a dual-wavelength optical frequency standard based on the dual-optical-transition modulation transfer spectroscopy(DOT-MTS)between different quantum transitions of the rubidium D1(795 nm)and D2(780 nm)lines.In a single rubidium atomic ensemble,modulation frequency sidebands from the 780 nm pump beam are simultaneously transferred to both the 780 and 795 nm probe lasers.The DOT-MTS enables the simultaneous stabilization of 780 and 795 nm lasers on a single vapor cell.Both lasers exhibit a frequency instability in the low 10-14range at 1 s of averaging,as estimated from the residual error signal.A theoretical model is developed based on the V-type atomic level structure to illustrate the dual-wavelength spectroscopy.This approach can be extended to develop a multi-wavelength optical frequency standard within a single atomic ensemble,broadening its applicability in fields such as precision metrology,Rydberg atoms,wavelength standards,optical networks,and beyond.
基金Innovation Program for Quantum Science and Technology(2021ZD0303200)National Natural Science Foundation of China(62405007,624B2010)+1 种基金China Postdoctoral Science Foundation(BX2021020)Wenzhou Major Science and Technology Innovation Key Project(ZG2020046)。
文摘The transportable optical clock can be deployed in various transportation vehicles,including aviation,aerospace,maritime,and land-based vehicles;provides remote time standards for geophysical monitoring and distributed coherent sensing;and promotes the unmanned and lightweight development of global time network synchronization.However,the current transportable version of laboratory optical clocks is still limited by factors such as environmental sensitivity,manual maintenance requirements,and high cost.Here we report a single-person portable optical frequency standard using the recently proposed atomic-filter-based laser“Voigt laser”as the local oscillator.It is worth mentioning that due to the inherent characteristics of Voigt lasers,the Voigt optical frequency standard can maintain turn-key functionality under harsh environmental impacts without any manual maintenance requirement.In our experiment,conducted over a duration of 12 min,we subjected the laser diode to multiple temperature shocks,resulting in a cumulative temperature fluctuation of 15℃.Following each temperature shock event,the Voigt optical frequency standard automatically relocked and restored the frequency output.Therefore,this demonstration marks a significant technological breakthrough in automatic quantum devices and might herald the arrival of fully automated time network systems.
文摘This study investigates the application of miniature quantum references within small-scale optical atomic frequency standards,utilizing a diminutive^(87)Rb glass cell,dimensions of 6 mm×6 mm×6 mm,to establish a quantum frequency standard.'By employing the transition spectrum from 5^(2)S_(1/2)F=2 to 5^(2)P_(3/2)F=3,this study successfully demonstrates the development of a compact rubidium atomic optical frequency standard via modulation transfer spectroscopy(MTS).Subsequent to frequency stabilization,the 780 nm clock laser exhibits a linewidth of 6.9 k Hz,and its out-of-loop short-term stability reaches4.1×10^(-13)@1 s,as confirmed through beat frequency analysis.This research not only provides a practical blueprint for the development of small optical atomic frequency standards but also lays down essential groundwork for future advancements in chip-level optical frequency standard technologies.
文摘A compact extended cavity diode laser （ECDL） system operating at 852 nm for small optically pumped cesium （Cs） beam frequency standards was reported. ECDL and a saturated absorption spectroscopy setup were all built in an aluminum box with dimension of 10 × 10 × 7 （cm）. ECDL was based on a Littman-Metcaff configuration, whose free-running linewidth was less than 600 kHz. A digital automatic frequency lock unit （AFLU） was developed to lock the laser frequency to specify Cs absorption lines automatically and re-lock it in case of lock broken. With AFLU, the laser frequency was continuously locked for several weeks.
基金the National Key Basic Research and Development Programme of China under Grant No.2005CB724500.
文摘Calcium is one prospective element for the modern optical frequency standard. The 423-nm transition line of calcium atoms has been widely used in laser slowing and laser cooling, the precise spectrum measurement, and the magnetic optical trapping （MOT）. However, there is no any available commercial diode laser working at this wavelength. We built a 423-nm laser based on extra bow-tie cavity and by using a Brewstercut uncoated BIBO （BiB306） crystal, which worked at room temperature, with conversion efficiency of 3.75%, and a potential up to 20%.
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 National Fundamental Research Program of China (Grant Nos 2005CB3724500 and 2006CB921400)the Major Program of National Natural Science Foundation of China (Grant No 60490280)National Natural Science Foundation of China (Grant No 10574005)
文摘This paper reports that two identical external-cavity-diode-laser （ECDL） based spectrometers are constructed at 634nm referencing on the hyperfine B-X transition R（80）8-4 of 127I2. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8 × 10^-12 （after 1000 s） by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.
文摘Ultra-stable optical cavities are widely used for laser frequency stabilization. In these experiments the laser performance relies on the length stability of the Fabry-Perot cavities. Vibration-induced deformation is one of the dominant factors that affect the stability of ultra-stable optical cavities. We have quantitatively analysed the elastic deformation of Fabry-Perot cavities with various shapes and mounting configurations. Our numerical result facilitates a novel approach for the design of ultra-stable cavities that are insensitive to vibrational perturbations. This approach can be applied to many experiments such as laser frequency stabilization, high-precision laser spectroscopy, and optical frequency standards.
