CN112152079A - Optical pumping small cesium clock for modulating transfer spectrum frequency stabilization DFB laser and implementation method - Google Patents
Optical pumping small cesium clock for modulating transfer spectrum frequency stabilization DFB laser and implementation method Download PDFInfo
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- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 title claims abstract description 159
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- 238000001917 fluorescence detection Methods 0.000 claims description 2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/06817—Noise reduction
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- G—PHYSICS
- G04—HOROLOGY
- G04F—TIME-INTERVAL MEASURING
- G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
- G04F5/14—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
- H01S5/0687—Stabilising the frequency of the laser
Abstract
The invention discloses an optical pumping small cesium clock based on modulation transfer spectrum frequency stabilization DFB laser and a realization method, comprising a modulation transfer spectrum frequency stabilization DFB laser system, a light splitting flat sheet, an acousto-optic modulator, a vacuum physical system of the small cesium clock and a comprehensive circuit system of the small cesium clock; taking DFB laser for modulating transfer spectrum frequency stabilization as pumping light and detection light, carrying out lamb-plug interaction on a microwave excitation field generated by a vacuum physical system and cesium atoms, scanning the frequency of the microwave excitation field, and detecting the particle number of the cesium atoms in a ground state by the laser to obtain a clock transition spectral line signal; the integrated circuit system collects clock transition spectral line signals, and the clock transition spectral line signals are fed back to a crystal oscillator in the integrated circuit system through a modulation-demodulation servo control circuit to obtain clock signals with high frequency stability.
Description
Technical Field
The invention belongs to the technical field of microwave atomic clocks and microwave quantum frequency standards, and relates to an optical pumping small cesium clock for modulating transfer spectrum frequency stabilization (DFB) laser and an implementation method.
Background
The cesium atom microwave clock is widely applied to the fields of satellite positioning, high-precision spectrum, time keeping, time service and the like, and plays a crucial role in the field of quantum frequency standards. The commercial optical pumping small cesium clock has a considerable function in the fields of satellite navigation ground stations, digital communication synchronous networks, long waveguide route base stations and the like. The frequency stability of the commercial small cesium clock for optical pumping is closely related to the frequency stability of optical pumping laser, and the problem of solving the key technical problem of laser frequency stabilization is indispensable for improving the overall performance of the commercial small cesium clock.
The system of the optical pumping small cesium clock mainly comprises laser, a physical system and a circuit system, wherein if the laser part is in a free running state, the cavity length of the laser is influenced by temperature, air pressure and vibration to cause frequency drift along with time. At present, a laser part used for an optical pumping small cesium clock generally adopts a semiconductor laser combined with a saturation spectrum frequency stabilization technology or a polarization spectrum frequency stabilization technology to obtain frequency stabilized laser. The saturated spectrum frequency stabilization technology generally performs internal modulation on the frequency of a laser, modulation noise can affect the change of laser working current and temperature, a certain direct current background exists in the background of the obtained saturated spectrum, and the whole saturated spectrum is in a drifting state, so that the stability of the laser frequency is affected; compared with a saturated spectrum frequency stabilization technology, the polarized spectrum frequency stabilization technology effectively eliminates the drift of part of Doppler backgrounds, directly improves the short-term stability and the frequency locking effect of laser, but has a poor frequency stabilization effect in a low-frequency band, and meanwhile, the loop bandwidth influences the frequency locking range, so that the frequency locking range is narrow. Therefore, the selection of the laser and the frequency stabilization system in the currently commercially available optical pumping small cesium clock limits the further improvement of the frequency stability and accuracy of the small cesium clock.
The optical pumping small cesium clock based on the modulation transfer spectrum frequency stabilization narrow linewidth laser disclosed in the chinese patent application CN201910738468.3 is mainly directed at the optical pumping small cesium clock of the modulation transfer spectrum frequency stabilization external cavity semiconductor laser narrow linewidth laser, and the function of the optical pumping small cesium clock is limited in that the narrow linewidth laser of the external cavity type structure is sensitive to temperature and mechanical vibration, and mode hopping easily occurs, and long-term frequency locking can be realized only by a special intelligent control technology. In addition, the optical pumping cesium atomic clock using the axisymmetric multi-stage magnet disclosed in the chinese patent application CN 2019109616524 mainly solves the problem of atom utilization efficiency by performing spatial focusing on cesium atoms through an axisymmetric six-stage magnet beam optical system.
Disclosure of Invention
In order to solve the problem that the frequency stability and the frequency accuracy of a commercial optical pumping small cesium clock are limited by a high-performance laser with long-term frequency stabilization and a signal-to-noise ratio of a related laser detection clock signal, the invention provides the optical pumping small cesium clock with the modulation transfer spectrum frequency stabilization DFB laser and a realization method thereof.
The modulation transfer spectrum frequency stabilization DFB laser system obtains DFB laser with stable frequency by utilizing a DFB laser and a modulation transfer spectrum frequency stabilization system, and is additionally provided with a frequency stabilization system on the basis of the DFB laser. The invention applies the modulation transfer spectrum frequency stabilization DFB laser in the optical pumping small cesium clock, and the technical advantages are as follows: firstly, in the existing academic documents and invention patents, the fact that laser pumping small cesium clock is realized by using DFB laser for modulating transfer spectrum frequency stabilization does not appear, the invention provides a novel DFB laser for modulating transfer spectrum frequency stabilization as optical pumping small cesium clock for pumping laser and detecting laser, and the signal-to-noise ratio of small cesium clock signals is improved by orders of magnitude; secondly, the laser frequency fluctuation obtained in the existing modulation transfer spectrum frequency stabilization technology is in the order of hundred kHz, the feedback signal obtained after the DFB laser passes through the modulation transfer spectrum frequency stabilization system is directly applied to the DFB laser to realize frequency noise suppression in a larger bandwidth range, the continuous frequency locking frequency stabilization DFB laser with lower frequency noise is realized, the laser frequency fluctuation is optimal and can reach the order of tens of Hz, the laser frequency fluctuation is improved by four orders of magnitude compared with the prior art, and the technical parameter is remarkably improved. And compared with an external cavity semiconductor laser, the DFB laser has the advantages of small volume, stable performance, convenient temperature control integration, capability of achieving hundred GHz longitudinal mode interval and special advantages for reducing the volume, weight and power consumption of a commercial small cesium clock. Finally, the DFB laser based on modulation transfer spectrum frequency stabilization provided by the invention has strong applicability, and can be applied to the basic research fields of precision instruments such as an atomic magnetometer and a laser gyroscope, as well as precision spectrum research and the like.
Compared with the optical pumping small cesium clock based on the modulation transfer spectrum frequency stabilization narrow linewidth laser disclosed by CN201910738468.3, the DFB laser disclosed by the invention has the advantages of small volume, no vibration influence, very easy temperature control, no mode hopping interval up to 300GHz, and optimal frequency fluctuation up to dozens of Hz magnitude after the modulation transfer spectrum technology is combined.
The invention relates to an optical pumping small cesium clock of a modulation transfer spectrum frequency stabilization DFB laser, which comprises: a modulation transfer spectrum frequency stabilization DFB laser system, a light splitting flat sheet, an acousto-optic modulator, a vacuum physical system of a small cesium clock and a comprehensive circuit system of the small cesium clock. Wherein the vacuum physical system of the small cesium clock provides quantum frequency reference for the optical pumping small cesium clock; the integrated circuit system of the small cesium clock comprises a crystal oscillator and a modulation-demodulation servo control circuit. The modulation transfer spectrum frequency stabilization DFB laser system is connected with the beam splitting flat sheet, the DFB frequency stabilization laser is divided into two beams after passing through the beam splitting flat sheet, one beam is used as pumping laser after being frequency shifted by the acousto-optic modulator, the other beam is used as detection laser, the two beams of pumping laser and the detection laser enter a vacuum physical system of the small cesium clock, and the vacuum physical system of the small cesium clock is connected with a comprehensive circuit system of the small cesium clock.
Specifically, DFB frequency stabilized laser output by a modulation transfer spectrum frequency stabilized DFB laser system is divided into two laser beams by a beam splitter, one laser beam is frequency-shifted to negative first-order diffraction light by an acousto-optic modulator and is used as pumping laser of a vacuum physical system of a small cesium clock, and the pumping laser corresponds to cesium atoms 6S1/2F＝4—6P3/2The transition of F' ═ 4, another light is used as the detection laser of vacuum physical system of small cesium clock, corresponding to 6S of cesium atom1/2F＝4—6P3/2F' is a transition of 5. The pumping laser will be at 6S1/2All cesium atoms in the small cesium clock vacuum physical system in the F-4 state are pumped to 6S1/2F-3 state, microwave exciting field generated by vacuum physical system of small cesium clock and cesium atomPerforming a lambda plug interaction to bring the temperature to 6S1/2Transition of an atom in the 3-state to 6S1/2F is 4 state. Detection laser pair 6S1/2Detecting the particle number of 4-state cesium atoms to obtain clock transition spectral line signals; clock transition spectral line signals are collected by a comprehensive circuit system of the small cesium clock, and are fed back to a crystal oscillator in the comprehensive circuit system of the small cesium clock by a modulation-demodulation servo control circuit in the comprehensive circuit system of the small cesium clock to obtain stable control with ultrahigh stability, so that the small cesium clock can be optically pumped by modulation-transition spectrum frequency-stabilized DFB laser which can continuously operate for a long time.
The drive power supply of the DFB laser is provided with a laser current feedback port and other high-speed response ports, the DFB laser is provided with an external modulation response port, and the DFB laser can realize higher-precision control on laser frequency in an external input signal mode. When the DFB laser passes through the modulation transfer spectrum frequency stabilization system, the obtained feedback signal is directly applied to the DFB laser to realize frequency noise suppression in a larger bandwidth range, so that a high-speed stable signal feedback mechanism is realized, and the DFB laser with lower frequency noise and continuous frequency locking is realized.
Preferably, the DFB laser in the optical pumping small cesium clock system for modulating the shift spectrum frequency stabilized DFB laser can be a dbr (distributed Bragg reflector) semiconductor laser or the like.
Preferably, the acousto-optic modulator in the optical pumping small cesium clock for modulating the frequency stabilized DFB laser can be a frequency shifting device such as an electro-optic modulator.
Preferably, in the optical pumping small cesium clock for modulating the transfer spectrum frequency stabilization DFB laser, in order to enable the laser and the atomic beam to interact sufficiently, the beam expander can be used to enlarge the size of the light spot before the pumping laser and the detection laser enter a vacuum physical system of the small cesium clock, so that the light spot can completely cover the atomic beam, and the signal-to-noise ratio of the clock spectral line signal can be improved.
Another objective of the present invention is to provide a method for implementing an optical pumping small cesium clock for a modulation transfer spectrum frequency stabilized DFB laser, which includes the following steps:
1) the laser power supply drives a frequency stabilization DFB laser based on a modulation transfer spectrum to output DFB frequency stabilization laser, the DFB frequency stabilization laser is divided into two beams of laser through a beam splitter, one beam of laser is subjected to frequency shift to negative first-order diffraction light through an acousto-optic modulator and is used as pumping light of a vacuum physical system of the small cesium clock, and the other beam of laser is used as detection light of the vacuum physical system of the small cesium clock;
2) the detection laser vertically interacts with cesium atoms in a vacuum physical system of the small cesium clock, a fluorescence detector detects and obtains a cesium atom cyclic transition spontaneous emission signal, and the pumping laser pair is in 6S1/2All atoms in the F-4 state are pumped to 6S1/ 2F is 3 state;
3) the microwave excitation field generated by the vacuum physical system of the small cesium clock interacts with atoms in a lamb-plug manner to be at 6S1/2Transition of an atom in the 3-state to 6S1/2F is 4 state;
4) the frequency of a microwave excitation field is scanned, clock transition spectral line signals obtained by fluorescence detection are collected by a comprehensive circuit system of the small cesium clock, and are fed back to a crystal oscillator in the comprehensive circuit system of the small cesium clock by a modulation-demodulation servo control circuit in the comprehensive circuit system of the small cesium clock, so that ultrahigh-stability frequency control is obtained, and the optical pumping of the modulation-transition-spectrum frequency-stabilized DFB laser capable of continuously running for a long time is realized.
In step 1), the DFB laser in the optical pumping small cesium clock system for modulating the transfer spectrum frequency stabilized DFB laser can be a dbr (distributed Bragg reflector) semiconductor laser or the like.
In the step 1), the acousto-optic modulator in the optical pumping small cesium clock system for modulating the frequency-stabilized DFB laser of the transfer spectrum can be a frequency shift device such as an electro-optic modulator;
in the step 2), in order to enable the laser and the atomic beam to interact sufficiently, the size of a light spot can be enlarged by a beam expander before the pumping laser and the detection laser enter a vacuum physical system of the small cesium clock, so that the light spot can completely cover the atomic beam, and the signal-to-noise ratio of a spectral line signal is improved.
In step 3), the microwave excitation field can be directly generated by a microwave signal source in the optical pumping small cesium clock of the modulation transfer spectrum frequency stabilization DFB laser.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides an optical pumping small cesium clock system device for modulating a transfer spectrum frequency stabilization DFB laser and an implementation method, and the technical advantages are as follows:
1. in the prior academic documents and invention patents, the fact that laser pumping small cesium clock is realized by using DFB laser for modulating transfer spectrum frequency stabilization does not appear, the invention provides a novel DFB laser for modulating transfer spectrum frequency stabilization as the optical pumping small cesium clock for pumping laser and detecting laser, and the signal-to-noise ratio of small cesium clock signals is improved by orders of magnitude;
2. the laser Frequency fluctuation obtained in the existing modulation transfer spectrum Frequency stabilization technology is in the order of hundred kHz ("Frequency stability of DFB laser via modulation transfer spectrum", "Proc. SPIE 10256, Second International Conference on Photonics and Optical Engineering, 102560P"), the feedback signal obtained after the DFB laser is modulated by the modulation transfer spectrum Frequency stabilization system is directly applied to the DFB laser to realize Frequency noise suppression in a larger bandwidth range, and the continuous Frequency locking Frequency stabilization DFB laser with lower Frequency noise is realized, the laser Frequency fluctuation of the DFB laser can optimally reach the order of tens of Hz, the laser Frequency fluctuation is improved by four orders of magnitude compared with the prior art, and the technology parameter is remarkably improved.
3. Compared with an external cavity semiconductor laser, the DFB laser has the advantages of small volume, stable performance, convenient temperature control integration, capability of achieving hundred GHz longitudinal mode spacing, and special advantages for reducing the volume, weight and power consumption of a commercial small cesium clock.
4. The DFB laser for modulating the transfer spectrum and stabilizing the frequency provided by the invention has strong applicability, and can be applied to the basic research fields of precision instruments such as an atomic magnetometer and a laser gyroscope, precision spectrum research and the like.
The invention combines the DFB laser, the modulation transfer spectrum frequency stabilization technology and the large bandwidth feedback technology, can improve the signal-to-noise ratio of the transition spectral line of the optical pumping small cesium clock by several orders of magnitude, and realizes the optical pumping small cesium clock which has ultrahigh performance index and can continuously operate for a long time. The invention can break through the bottleneck that the commercial optical pumping small cesium clock is limited by a high-performance laser with long-term frequency stabilization and the signal-to-noise ratio of the related laser detection clock signal, and further realizes the high-performance commercial optical pumping small cesium clock.
Drawings
Fig. 1 is a schematic structural diagram of a small cesium clock system for modulating, transferring and spectrally stabilizing DFB laser frequency in an embodiment of the present invention;
wherein: 1-modulation transfer spectrum frequency stabilization DFB laser system, 2-beam splitter, 3-acousto-optic modulator, 4-small cesium clock vacuum physical system and 5-small cesium clock integrated circuit system.
Detailed Description
The invention is further explained below with reference to the drawings and examples.
The invention provides an optical pumping small cesium clock for a modulation transfer spectrum frequency stabilization DFB laser, which comprises: a modulation transfer spectrum frequency stabilization DFB laser system, a light splitting flat sheet, an acousto-optic modulator, a vacuum physical system of a small cesium clock and a comprehensive circuit system of the small cesium clock. In specific implementation, DFB frequency stabilized laser output by a modulation transfer spectrum frequency stabilized DFB laser system is divided into two laser beams by a beam splitter, one laser beam is frequency-shifted to negative first-order diffraction light by an acousto-optic modulator and is used as pumping laser of a vacuum physical system of a small cesium clock, and the pumping laser corresponds to cesium atoms 6S1/2F＝4—6P3/2The transition of F' ═ 4, another light is used as the detection laser of vacuum physical system of small cesium clock, corresponding to 6S of cesium atom1/2F＝4—6P3/2F' is a transition of 5. The pumping laser will be at 6S1/2All cesium atoms in the small cesium clock vacuum physical system in the F-4 state are pumped to 6S1/2F-3 state, microwave exciting field generated by vacuum physical system of small cesium clock and cesium atom are subjected to lamb-plug interaction to make it be in 6S1/2Transition of an atom in the 3-state to 6S1/2F is 4 state. Detection laser pair 6S1/2Detecting the particle number of 4-state cesium atoms to obtain clock transition spectral line signals; the clock transition spectral line signal is collected by the integrated circuit system of the small cesium clock and is demodulated by the modulation in the integrated circuit system of the small cesium clockThe adjusting servo control circuit feeds back to a crystal oscillator in an integrated circuit system of the small cesium clock to obtain stable control with ultrahigh stability, so that the small cesium clock can be optically pumped by the modulation transfer spectrum frequency stabilization DFB laser which can continuously operate for a long time.
The drive power supply of the DFB laser is provided with a laser current feedback port and other low-speed response ports, the DFB laser is provided with an external modulation response port, the DFB laser can realize higher-precision control on laser frequency in an external input signal mode, in the prior art, the response bandwidth of the laser current and other low-speed response ports is low, and the external modulation response port of the DFB laser can suppress frequency noise in a wider range. When the DFB laser passes through the modulation transfer spectrum frequency stabilization system, the obtained feedback signal is directly applied to the DFB laser to realize frequency noise suppression in a larger bandwidth range, so that a high-speed stable signal feedback mechanism is realized, and the DFB laser with lower frequency noise and continuous frequency locking is realized.
In specific implementation, the DFB laser in the optical pumping small cesium clock system for modulating the frequency-stabilized DFB laser with a shifted spectrum can be a DBR semiconductor laser and the like.
In specific implementation, the acousto-optic modulator in the optical pumping small cesium clock for modulating the frequency-stabilized DFB laser of the transfer spectrum can be a frequency shift device such as an electro-optic modulator.
In the specific implementation, in the optical pumping small cesium clock for modulating the transfer spectrum frequency stabilization DFB laser, in order to enable the laser and the atomic beam to fully interact, the beam expander can be used for expanding the size of a light spot before the pumping laser and the detection laser enter a vacuum physical system of the small cesium clock so as to enable the light spot to fully cover the atomic beam, and the signal-to-noise ratio of a clock spectral line signal is improved.
In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below. Fig. 1 is a schematic structural diagram of a small cesium clock system for a modulation-shifted spectrum frequency-stabilized DFB laser according to an embodiment of the present invention; . A small cesium clock system for modulating a transferred-spectrum frequency stabilized DFB laser comprising: a modulation transfer spectrum frequency stabilization DFB laser system 1, a beam splitter 2, an acousto-optic modulator 3, a vacuum physical system 4 of a small cesium clock and a comprehensive circuit system 5 of the small cesium clock.
The laser output by the modulation transfer spectrum frequency stabilization DFB laser system 1 is divided into two laser beams by a beam splitter 2, one laser beam is subjected to frequency shift to negative first-order diffraction light by an acousto-optic modulator 3 and is used as pumping laser of a vacuum physical system 4 of a small cesium clock, and the pumping laser corresponds to cesium atoms 6S1/ 2F＝4—6P3/2The transition of F' ═ 4, another light is used as the detection laser of vacuum physical system 4 of small cesium clock, corresponding to 6S of cesium atom1/2F＝4—6P3/2F' is a transition of 5. Vacuum physical system 4 for pumping laser to small cesium clock is at 6S1/2Abstraction of an atom in the 4-F state to 6P3/2F' ═ 4 state, 6P3/2Atoms in the F ═ 4 state spontaneously radiate to 6S1/2F-3 state and 6S1/2F-4 state, with atoms in 6S under continuous pumping1/2Abstraction of atoms in the 4-F state to 6S1/2F is 3 state. The microwave excitation field generated by the vacuum physical system 4 of the small cesium clock performs a lamb-plug interaction with the atoms to be at 6S1/2Transition of an atom in the 3-state to 6S1/2F is 4 state. Detection laser pair 6S1/2The number of particles in the state F-4 is detected, the obtained clock transition spectral line signal is collected by the integrated circuit system 5 of the small cesium clock, and a modulation-demodulation servo control circuit in the integrated circuit system 5 of the small cesium clock feeds back to a crystal oscillator in the integrated circuit system 5 of the small cesium clock to obtain stable control with ultrahigh stability, so that the optical pumping small cesium clock based on the modulation transfer spectrum frequency stabilization DFB laser which can continuously operate for a long time is realized.
When the invention is implemented, a feedback signal obtained after the DFB laser passes through the modulation transfer spectrum frequency stabilization system is directly applied to the DFB laser to realize frequency noise suppression in a larger bandwidth range. The frequency-stabilized detection light and the pumping light can be respectively subjected to light intensity control, and the maximum error signal is obtained by optimizing the light intensity ratio, so that the laser frequency of the system can be conveniently locked; the frequency stabilized DFB laser in an optically pumped small cesium clock system can be a DBR semiconductor laser or the like. The acousto-optic modulator in the optical pumping small cesium clock can be a frequency shift device such as an electro-optic modulator. In order to enable the laser and the atomic beam to fully interact, before pumping the laser and the detection laser enter a vacuum physical system of a small cesium clock, a light spot can be enlarged through a beam expander to enable the laser and the detection laser to completely cover the atomic beam, and the signal-to-noise ratio of a spectral line signal is improved.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the working principle of the present invention, and are not used to limit the scope of the present invention. In particular, in order to provide a frequency stabilization system for commercial stabilized lasers, the invention is applicable to frequency-stabilized DFB lasers or DBR lasers based on modulation-shifted spectra, which are well known to those skilled in the art and therefore will not be described in detail. It will be understood by those skilled in the art that various modifications and equivalent substitutions may be made to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Therefore, the protection scope of the present invention is subject to the limitation of the claims.
Claims (10)
1. A method for realizing an optical pumping small cesium clock of a modulation transfer spectrum frequency stabilization DFB laser comprises the following steps:
1) the laser power supply drives the modulation transfer spectrum frequency stabilization DFB laser to output DFB frequency stabilization laser which is divided into two beams of laser by the beam splitting flat sheet; one laser beam is shifted to negative first-order diffraction light through an acousto-optic modulator and is used as pumping light of a vacuum physical system of the small cesium clock; another laser is used as the probe light of a vacuum physical system of the small cesium clock;
2) detecting the vertical interaction of laser and cesium atoms in a vacuum physical system of the small cesium clock, and detecting by a fluorescence detector to obtain a cesium atom cyclic transition spontaneous emission signal; the pumping laser will be at 6S1/2All cesium atoms in F-4 state are pumped to 6S1/2F is 3 state;
3) microwave excitation field generated by vacuum physical system of small cesium clock is subjected to lamb-plug interaction with cesium atoms to make the cesium atoms be at 6S1/2Transition of cesium atom in F-3 state to 6S1/2F is 4 state;
4) scanning the frequency of a microwave excitation field, performing fluorescence detection to obtain clock transition spectral line signals, and collecting the clock transition spectral line signals by a comprehensive circuit system of a small cesium clock; feeding back a modulation and demodulation servo control circuit in the integrated circuit system of the small cesium clock to a crystal oscillator in the integrated circuit system of the small cesium clock to obtain frequency control with ultrahigh stability;
through the steps, the optical pumping small cesium clock of the modulation transfer spectrum frequency stabilization DFB laser capable of continuously running for a long time is realized.
2. The method for implementing an optically pumped small cesium clock for a modulation-shifted spectrum frequency stabilized DFB laser as claimed in claim 1, wherein in step 1), the modulation-shifted spectrum frequency stabilized DFB laser employs a modulation-shifted spectrum frequency stabilized DBR semiconductor laser.
3. The method for implementing the optically pumped small cesium clock for the modulation of the frequency stabilized DFB laser of claim 1, wherein in step 1), the acousto-optic modulator is a frequency shifting device, including an electro-optic modulator.
4. The method for implementing the optical pumping small cesium clock for modulating the shifted spectrum frequency stabilized DFB laser according to claim 1, wherein in step 2), before the pumping laser and the detection laser enter a vacuum physical system of the small cesium clock, the beam expander expands the size of a light spot, so that the atomic beam is completely covered, and the laser and the atomic beam sufficiently interact with each other, thereby improving the signal-to-noise ratio of the spectral line signal.
5. The method for implementing an optically pumped small cesium clock for a modulation transfer spectrum frequency stabilized DFB laser as claimed in claim 1, wherein in step 3), the microwave excitation field is directly generated by a microwave signal source.
6. An optical pumping small cesium clock for modulating a transfer spectrum frequency stabilized DFB laser is characterized by comprising the following components: a modulation transfer spectrum frequency stabilization DFB laser system, a light splitting flat sheet, an acousto-optic modulator, a vacuum physical system of a small cesium clock and a comprehensive circuit system of the small cesium clock; the DFB laser system for modulating and transferring spectrum frequency stabilization is used for emitting DFB frequency stabilization laser; the vacuum physical system of the small cesium clock is used for providing quantum frequency reference for the optical pumping small cesium clock; the integrated circuit system of the small cesium clock comprises a crystal oscillator and a modulation-demodulation servo control circuit;
the modulation transfer spectrum frequency stabilization DFB laser system is connected with the light splitting plain film; the DFB frequency stabilization laser emitted by the DFB laser system for modulating the transfer spectrum frequency stabilization is divided into two beams after passing through the beam splitter, one beam is used as pumping laser after being subjected to frequency shift by the acousto-optic modulator, and the other beam is used as detection laser; pumping laser and detection laser into a vacuum physical system of the small cesium clock, wherein the vacuum physical system is connected with a comprehensive circuit system;
a microwave excitation field generated by a vacuum physical system performs lamb-plug interaction with cesium atoms to enable the cesium atoms to jump; detecting the particle number of transition cesium atoms by using detection laser to obtain clock transition spectral line signals; the integrated circuit system collects clock transition spectral line signals, and the signals are fed back to a crystal oscillator in the integrated circuit system by a modulation-demodulation servo control circuit in the integrated circuit system to obtain frequency control with ultra-high stability, so that the small optical pumping cesium clock of the modulation-transition-spectrum frequency-stabilized DFB laser capable of continuously running for a long time is formed.
7. The optical pumping small cesium clock for the modulation transfer spectrum frequency stabilized DFB laser as claimed in claim 6, wherein the DFB frequency stabilized laser is divided into two laser beams by a beam splitter, one laser beam is frequency-shifted to the minus first order diffraction light by an acousto-optic modulator, and the laser beam is used as the pumping laser of the vacuum physical system of the small cesium clock corresponding to the cesium atom 6S1/2F＝4—6P3/2F ═ 4 transitions; another laser is used as the detection laser of the vacuum physical system of the small cesium clock, and the laser corresponds to the 6S of cesium atoms1/2F＝4—6P3/2F' is a transition of 5; the pumping laser will be at 6S1/2All cesium atoms in the small cesium clock vacuum physical system in the F-4 state are pumped to 6S1/2F is 3 state, microwave excitation field generated by vacuum physical system and cesium atom are subjected to lamb-plug interaction to make F be in 6S1/2Transition of an atom in the 3-state to 6S1/2F is 4 state; detection laser pair 6S1/2And F is the particle number of 4-state cesium atoms, and a clock transition spectral line signal is obtained.
8. The optical pumping small cesium clock for the modulation transfer spectrum frequency stabilization DFB laser according to claim 6, wherein a driving power supply of the DFB laser is provided with a laser current feedback port and a high-speed response port, and the DFB laser is provided with an external modulation response port, so that the laser frequency can be controlled at higher precision in an external signal input mode, and frequency noise in a wider range can be suppressed; when the DFB laser passes through the modulation transfer spectrum frequency stabilization system, the obtained feedback signal is directly applied to the DFB laser to realize frequency noise suppression in a larger bandwidth range, so that a high-speed stable signal feedback mechanism is realized, and the DFB laser with lower frequency noise and continuous frequency locking is realized.
9. The optical pumping small cesium clock for the modulation-transferred-spectrum frequency-stabilized DFB laser as claimed in claim 6, wherein the DFB laser is a DBR semiconductor laser; and/or the acousto-optic modulator is an electro-optic modulator frequency shift device.
10. The optical pumping small cesium clock for the modulation transfer spectrum frequency stabilization DFB laser according to claim 6, wherein before pumping laser and detection laser enter a vacuum physical system, the spot size is enlarged by a beam expander so as to completely cover the atomic beam current.
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