CN100589049C - Coherent maser radiation cold atomic clock - Google Patents
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- CN100589049C CN100589049C CN200710053214A CN200710053214A CN100589049C CN 100589049 C CN100589049 C CN 100589049C CN 200710053214 A CN200710053214 A CN 200710053214A CN 200710053214 A CN200710053214 A CN 200710053214A CN 100589049 C CN100589049 C CN 100589049C
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Abstract
The present invention discloses a coherent microwave-radiation cold atomic clock; and an ion pump is connected with a vacuum catheter which is connected with a microwave cavity; a light window is fixed in the microwave cavity by quartz glass and three reflective mirrors; a pair of anti-Helmholtz coils and a pair of Helmholtz coils are fixed on the microwave cavity; a pair of rectangular coils arefixed on the microwave cavity; a magnetic shielding system is connected with a vacuum system; semiconductor laser provides captive light and beams of pump-back light; a semiconductor laser on the vertical cavity surface provides a plurality of beams of captive light; a voltage-controlled crystal oscillator is connected with a frequency synthesizers connected with a signal receiver and processor; the semiconductor laser on the vertical cavity surface is connected with the microwave cavity; a photoelectric detector and a microwave-power receiver are connected with the signal receiver and processor connected with the voltage-controlled crystal oscillator as well as the semiconductor laser on the vertical cavity surface. The present invention is characterized in that the structure is compact and the size is small, and has good stability, high accuracy as well as good applicability.
Description
Technical field
The present invention relates to a kind of atomic clock field, more specifically relate to a kind of coherent maser radiation cold atomic clock, cold atom with the thick optical thickness in the strip magneto-optic trap is an operation material, under microwave cavity and laser sideband effect through the microwave modulation, utilize the absorbing detection signal of relevant population number imprison and the microwave power acknowledge(ment) signal genlocing vertical-cavity-face emitting semiconductor laser and the VCXO of relevant microwave radiation, be applicable to fields such as punctual, time service, range finding, navigation, location, call duration time be synchronous.
Background technology
In the past 50 years, atomic frequency standard has had considerable progress.The stability of active hydrogen atomic clock is 10
-16Magnitude, the accuracy of caesium atom fountain clock is better than 1 * 10
-15Consider that from practical angle the stable frequency standard of miniaturization has widely to be used, such as caesium-beam clock and optical pumping rubidium clock.Traditional atomic clock utilizes transition between two ground state of hydrogen atom or alkali metal atom as the resonant transition frequency reference of atom, usually survey with mr techniques, with the preparation of magnetic field space separation or optical action realization atomic state, to strengthen the resonant probe signal.Hydrogen atom or alkali metal atom are as the atomic resonance frequency benchmark, jump frequency between the hyperfine energy level of two ground state is in microwave range, can survey by traditional mr techniques, the predicable of its implementation is the use that attitude is selected, by the magnetic spatial deviation, by the optical pumping effect, in the former subensemble after the attitude preparation, the resonant probe signal is enhanced.In recent years, along with the development of laser-cooling technology, the new physical mechanism of realizing atomic clock also in exploration, such as, relevant population number imprison clock, optical frequency standard (light clock).Bring into schedule as the cold atomic clock of actuating medium with cold atom, it has effectively reduced the Doppler effect of physical signalling, and its accuracy is better than with the similar atomic clock of hot atom as actuating medium with stability,
When the interaction of research laser and atom, the atomic coberent of induced with laser and quantum interference phenomenon merit attention, and G.Orriols etc. observed the atomic coberent effect with the dual-mode laser device in 1976 in the fine structure of sodium (Na) atom.Λ type Three-level Atom (two ground state, an excited state, have only and have two dipole transitions between ground state and the excited state) do the time spent with two laser fields, if the two-photon resonance condition is satisfied in the coupling of light field and atom, the population number of atom will be trapped on the stack attitude of two ground state, this attitude is called as dark attitude, and the atom that is in dark attitude does not interact with light field, no longer absorbs photon and transits to excited state.Relevant population number imprison in the alkali metal atom is for realizing that atomic clock provides a kind of effective method.Can observe this phenomenon with diverse ways, can observe narrow " a deceiving " line in the fluorescence spectrum of optical pumping assemblage, in absorbing detection, system does not absorb energy and becomes transparent when satisfying two-photon resonance.Therefore, this phenomenon shows as black line (being commonly referred to as concealed wire) in fluorescent radiation, in the propagate radiation field, show as the enhancing (usually being called bright line) of resonance transmission, this resonance effect has reflected all character of alkali metal atom ground state hyperfine resornance, can be used for realizing atomic frequency standard, be similar to the classic method that use microwave-optical pumping double resonance realizes atomic clock.People such as Thomas have successfully realized for the first time the similar application of this phenomenon, in these experiments, only use the Ramsey light beam of no microwave cavity, will be used to realize a kind of interaction zone of separation oscillating field of Ramsey type based on this phenomenon of sodium atom bundle.In middle nineteen nineties in last century, begun to imprison the relevant population in unit and counted the trial that phenomenon is used to realize the application of small-sized atomic frequency standard.In normal circumstances, the optical thickness of hot atom glass envelope is subjected to the control of buffer gas pressure and alkali metal atom density, and the former widens the absorption line width, and the latter influences optical absorption.In practice, operating temperature will make assemblage become the medium of optical thickness (Rb:T＞50 ℃, Cs:T＞40 ℃), and requires more meticulous design.But in the cold atom assemblage, the optical thickness of atom links together atomic ground state and excited state with circularly polarized light ground state m by the density and the temperature decision of atom
F=0 → m
F '=0 transition is desirable the selection, to reduce the influence of magnetic field to the atomic clock accuracy.
Up to now, the realization of atomic clock, comprise initiatively or passive, the light beam form or contain buffer gas closed cell form, comprised that cold atom medium, hot atom add buffer gas, but index is not very high yet.Aspect the miniaturization of atomic clock, the product that steeps atomic clock based on the room temperature of relevant population number imprison principle comes out, the relevant population number imprison of the normal temperature that U.S. Kernco company produces clock is subjected to the restriction that atomic spectral line Doppler widens, the live width of atomic spectral line is not ideal enough, its stability is all on the low side, is generally 10
-11To 10
-12In China, the relevant population number imprison cold atomic clock of having applied for is to adopt traditional magneto-optic trap as the cold atom medium, the acousto-optic modulator of high frequency produces the coupling light of relevant population number imprison light and surveys light, with the locking of the relevant population number imprison signal of surveying light to VCXO, this system utilizes the transparent method of traditional electromagnetically induced to realize relevant population number imprison cold atomic clock.Its advantage is to utilize the relevant population number imprison of cold atom semaphore lock VCXO to realize atomic clock, but also existing defective aspect the atomic clock of realizing high target, its reason is that the time of light and atomic interaction is shorter, the short halfwidth that is unfavorable for reducing relevant population number imprison signal of transit time, be used for the not locking of frequency of the narrow linewidth semiconductor laser of relevant population number imprison, its accuracy and stability are not high, are unfavorable for the miniaturization of atomic clock yet.
The fellowship of microwave and coherent light can be realized the microwave radiation that is concerned with being similar to active hydrogen atomic clock.Two optocoupler unification three-lever systems (two ground state and an excited state), when two light satisfy the condition of two-photon resonance, concealed wire appears when fluorescence detection, bright line appears when absorbing detection, the coherent radiation that can occur microwave power when surveying the radiation power of microwave simultaneously strengthens, the derivation and the explanation of detailed theory this have been done at J.Vanier in 1998, the linear of microwave coherent radiation is Lorentz line shape when the modulating frequency of scan laser, and radiation power and live width all have theoretical calculating and explanation.The relevant population number imprison of relevant microwave radiation signal has higher signal to noise ratio (S/N ratio), realizing the population number imprison cold atomic clock that initiatively is concerned with, i.e. all there is the advantage of self aspects such as the stability of miniaturization of coherent maser radiation cold atomic clock and raising atomic clock, accuracy.
Summary of the invention
The objective of the invention is to be to provide a kind of coherent maser radiation cold atomic clock, the magnetic light trap system of employing strip solves atom and short problem of light interaction transit time in the relevant population number imprison of cold atom by the optical thickness that increases cold atom group; Adopt the relevant microwave radiation population number of realizing initiatively being concerned with to imprison, the absorbing detection signal of the relevant population number imprison of utilization and relevant microwave irradiation power detectable signal are realized the genlocing to vertical-cavity-face emitting semiconductor laser and voltage controlled oscillator, solve the be concerned with accuracy of population number imprison cold atomic clock and the problem of stability.This atomic clock compact conformation, volume is little, and stability and accuracy are good, practical.
In order to achieve the above object, the present invention is by the following technical solutions:
A kind of coherent maser radiation cold atomic clock, it comprises vacuum system, catoptron, beam splitter, quarter-wave plate, anti-Helmholtz coils, Helmholtz coils, square coil, the magnetic field shielding system, semiconductor laser, vertical-cavity-face emitting semiconductor laser, photodetector, the microwave power receiver, signal receiving processor, VCXO and frequency synthesizer constitute, it is characterized in that the vacuum system shielding is in the magnetic field shielding system, vacuum system comprises ionic pump, vacuum pipeline, microwave cavity, quartz window, ionic pump links to each other with vacuum pipeline, vacuum pipeline links to each other with microwave cavity, on vacuum pipeline and the microwave cavity quartz window is arranged, quartz window is as logical light window, three catoptrons are fixed in the microwave cavity, a pair of anti-Helmholtz coils and a pair of Helmholtz coils are fixed on the axial direction of microwave cavity, a pair of square coil is fixed on microwave cavity in the radial direction, semiconductor laser provides the imprison light beam and returns pump light beam, the relevant population number imprison of vertical-cavity-face emitting semiconductor laser output laser beam, VCXO links to each other with frequency synthesizer, frequency synthesizer and signal receiving processor, vertical-cavity-face emitting semiconductor laser links to each other with microwave cavity, photodetector links to each other with signal receiving processor with the microwave power receiver, and signal receiving processor links to each other with vertical-cavity-face emitting semiconductor laser with voltage controlled oscillator.
Form the strip magnetic light trap system by ionic pump, vacuum pipeline, microwave cavity, quartz window, catoptron, quarter-wave plate, semiconductor laser (cooling light is provided, returns pump light), beam splitter, lens cylindrical mirror orthopedic systems, sample source, anti-Helmholtz coils and square coil.Microwave cavity, anti-Helmholtz coils, Helmholtz coils and square coil are placed in the magnetic field shielding system.Vacuum pipeline and microwave cavity are connected to form vacuum system, and logical light window quartz window, catoptron are fixed on the microwave cavity inside surface at a certain angle provides the needed cooling of magneto-optic trap to imprison laser beam splitter, and sample source links to each other with the vacuum pipeline difference, select for use rubidium (
87Rb) atomic sample, cooled with laser
87The magneton energy level of the hyperfine structure of Rb atom (is selected m for use
F=0 → m
F '=0 transition, its frequency is 6.835GHz) jump frequency as the reference of atomic clock locking signal, effectively eliminated single order Zeeman effect.The magneto-optic trap is shielded in the magnetic field shielding system, has reduced the influence of stray magnetic field effectively.
Integrated effectively microwave cavity and vacuum system integrated, further reduced the volume of atomic clock, the combination of microwave cavity and the imprison of relevant population number has realized active relevant population number imprison, by vertical-cavity-face emitting semiconductor laser, beam splitter, quarter-wave plate and photodetector are formed the optical system of relevant population number imprison, a pair of Helmholtz coils provides constant magnetic field to guarantee the direction of quantization axle, output signal (10MHz) by voltage controlled oscillator links to each other with vertical-cavity-face emitting semiconductor laser electric current high frequency modulated end through the microwave signal (3.4GHz) that the frequency synthesizer frequency multiplication obtains, (two sidebands differ 6.8GHz to laser beam after the modulation, just in time are
87The ground state interval of Rb) the rectangular direction through rolling into a ball by cold atom along the direction in magnetic field behind the quarter-wave plate, the relevant population number imprison of absorbing detection signal process photodetector is sent into signal receiving processor.
VCXO links to each other with frequency synthesizer, the microwave input end of frequency multiplication microwave signal input microwave cavity and the electric current high frequency modulated end of vertical-cavity-face emitting semiconductor laser, the electric current low frequency modulations end of low frequency signal (10KHZ) input vertical-cavity-face emitting semiconductor laser and the reference edge of signal receiving processor, VCXO, frequency synthesizer, microwave power receiver, signal processor are formed closed circuit.Microwave signal (6.8GHz) after the output signal process frequency synthesizer frequency multiplication of VCXO is sent into microwave cavity, relevant microwave radiation signal is sent into signal receiving processor by the microwave power receiver, deviation correcting signal locking VCXO after the processing demodulation, absorbing detection signal by relevant population number imprison is handled the error signal locking vertical-cavity-face emitting semiconductor laser that obtains after the modulation through signal receiving processor, realizes genlocing vertical-cavity-face emitting semiconductor laser and VCXO.
By the voltage controlled oscillator of microwave power receiver, signal receiving processor, 10MHz and the closed loop locked loop of frequency synthesizer composed atom clock.The 10MHz signal of the voltage controlled oscillator output after stable is as the atomic clock frequency standard.Photodetector links to each other with signal receiving processor with the microwave power receiver, the signal reference edge of signal receiving processor links to each other with frequency synthesizer, the 10KHz signal of frequency synthesizer is sent into the electric current low frequency modulations end of vertical-cavity-face emitting semiconductor laser and the signal reference edge of signal receiving processor, signal after the demodulation of absorbing detection signal process signal receiving processor is sent into the frequency stabilization port of vertical-cavity-face emitting semiconductor laser, photodetector, signal receiving processor and vertical-cavity-face emitting semiconductor laser are formed the laser frequency stabilization loop, relevant microwave radiation signal is sent into voltage controlled oscillator through signal receiving processor, frequency synthesizer and vertical-cavity-face emitting semiconductor laser, microwave cavity, signal receiving processor, VCXO links to each other, VCXO, frequency synthesizer, the microwave power receiver, signal receiving processor forms atomic clock closed loop locked loop.
The present invention compared with prior art has the following advantages and effect:
(1) adopt strip magneto-optic trap to obtain the cold atom group of strip, relatively hot atom and traditional magneto-optic trap, both reduced the single order Doppler effect, increased the transit time of relevant population number imprison again, effectively reduce relevant population and counted the halfwidth of signal, thereby improved the accuracy and the stability of atomic clock.
(2) adopt cold atom as actuating medium, arranged longer coherence time, reduced because of pouring the collision frequency displacement that buffer gas causes than hot atom.
(3) adopt microwave modulation vertical cavity surface emitting laser technology to realize the needed two bundle laser of relevant population number imprison signal, guaranteed the phase stabilization of relevant population number imprison laser.Low frequency signal is modulated the electric current of vertical-cavity-face emitting semiconductor laser and is obtained error, deviation correcting signal.
(4) adopt relevant population number imprison signal and microwave coherent radiation power detectable signal to realize the closed loop locking of atomic clock, both stablized the frequency of laser instrument, locked voltage controlled oscillator again, improved the accuracy and the stability of atomic clock.
(5) adopt the integrated of microwave cavity and vacuum system, the binding cavity internal reflector is realized strip magneto-optic well structure, has effectively realized the miniaturization of atomic clock.
Description of drawings
Fig. 1 is a kind of structural representation of coherent maser radiation cold atomic clock.
Fig. 2 is a kind of radial section figure of microwave cavity.
Fig. 3 is the energy level diagram of the rubidium atom that a kind of coherent maser radiation cold atomic clock adopted.
Wherein, 1-microwave cavity, 1a-microwave cavity section, the 2-vacuum pipeline, 3-ionic pump, 4a, 4b, 4c-quartz window, the anti-Helmholtz coils of 5-, the 6-Helmholtz coils, 7-square coil, 8-magnetic field shielding system, 9,9a, 9b, the 9c-catoptron, 10-semiconductor laser, 11-beam splitter, 12-laser imprison light beam, 13-lens cylindrical mirror orthopedic systems, 13a-13b, 13c-13d, 13e-13f-laser cooling imprison light beam is right, 14-strip cold atom group, the 15-vertical-cavity-face emitting semiconductor laser, 16-beam splitter, the relevant population number imprison of 17-light beam, the 18-photodetector, 19-signal receiving processor, 20-atomic clock signal output terminal, the 21-VCXO, 22-frequency synthesizer, 23-sample source, 24-microwave power receiver, 25, the 26-quarter-wave plate.
Embodiment
Below in conjunction with accompanying drawing the present invention is described in further detail:
According to Fig. 1, Fig. 2 as can be known, vacuum system comprises ionic pump 3, vacuum pipeline 2, microwave cavity 1, first to the 3rd quartz window 4a, 4b, 4c, microwave cavity 1 and vacuum pipeline 2 weld together, first to the 3rd quartz window 4a is arranged on microwave cavity 1 and the vacuum pipeline 2,4b, 4c, first to the 3rd quartz window 4a, 4b, 4c is used for leading to light, first quartz window 4a surface plating 780nm, the anti-reflection film of 795nm, the anti-reflection film of second quartz window 4b surface plating 780nm, the anti-reflection film of the 3rd quartz window 4c surface plating 795nm, the quarter-wave plate plated film of the high-reflecting film of 780nm and 780nm, sample source 24 of welding on vacuum pipeline 2, sample source 24 and vacuum pipeline 2 adopt kapillary to be connected to form the vacuum differential effect, rubidium atom in the sample source 24 to microwave cavity 1 diffusion, adopts laser cooling and imprison technology that rubidium steam is trapped in microwave cavity 1 center with certain conductance rate.Three catoptron 9a, 9b, 9c are fixed on microwave cavity 1 interior angle and become 25 ° angle with tangent plane, in microwave cavity 1, with 25 ° fixed angle first to the 3rd catoptron 9a, 9b, 9c are arranged with tangent plane, light path divided beam system as imprison light and cooling light, the total reflection film of first, second catoptron 9a, 9b surface plating 780nm, the total reflection film of the quarter-wave plate of the 3rd catoptron 9c surface plating 780nm.After taking out in advance early stage through the vacuum pump group, keep the interior ultrahigh vacuum degree (10 of microwave cavity 1 with ionic pump 3
-7Pa).
The light path divided beam system comprises beam splitter 11, beam splitter 16, the 3rd quartz window 4c, the lens cylindrical mirror orthopedic systems 13 and first to the 3rd catoptron 9a, 9b, 9c, the light of semiconductor laser 10 outputs is divided into the two-way light beam through behind the beam splitter 11, light beam 13a after one road light beam reflects through beam splitter 16 sends into microwave cavity 1 axial direction, light beam 13a forms first cooling through light beam 13b after the 3rd quartz window 4c reflection and light beam 13a and imprisons light beam to (13a-13b to), the strip light beam that another road light beam 12 is shaped to through lens cylindrical mirror group 13 is imported the radial direction of microwave cavity 1, rectangular light beam 13c obtains light beam 13f after through the first catoptron 9a and second catoptron 9b reflection, light beam 13f obtains light beam 13e after through the 3rd catoptron 9c, light beam 13e and light beam 13f form the second cooling imprison light beam to (13e-13f to), light beam 13e obtains light beam 13d after through the second catoptron 9b and the first catoptron 9a, and light beam 13c and light beam 13d form the 3rd cooling imprison light beam to (13c-13d to).
Quadrupole coil comprises anti-Helmholtz coils 5 and square coil 7, and the quadripolar magnetic field of atom laser cooling and imprison is provided.
Strip magneto-optic trap comprises semiconductor laser 10, light path divided beam system, quadrupole coil, semiconductor laser 10 has comprised the laser of two frequencies, promptly imprison light and return pump light, semiconductor laser 10 can adopt commercial TA100 and DL100, output power is respectively greater than 500mW and 60mW, tuning wavelength is used to provide cooling imprison light and returns pump light at 780.24nm.Cooling imprison light and time pump light light beam are through quarter-wave plate 25 and light path divided beam system, form orthogonal first pair to the 3rd pair cooling imprison light beam to (13a-13b is right, 13e-13f is right, 13c-13d to), its polarization all is circular polarization, cooling imprison light beam to the acting in conjunction of quadripolar magnetic field under, on the axial direction of microwave cavity 1, form the atomic group 14 of strip.
Vertical-cavity-face emitting semiconductor laser 15 is selected ULM795-03-TN-S46FOP for use, usually output power is several mW, its wavelength tuning is near 795nm, its light beam is through the beam splitter 16 (high-reflecting film of surface plating 780nm, the anti-reflection film of 795nm) and behind the quarter-wave plate 26, along the long axis direction of axially sending into cold atom group 14 of microwave cavity 1, photodetector 18 is surveyed the absorption signal of relevant population number imprison light.The signal of photodetector 18 is sent into signal receiving processor 19 and is handled demodulation.
Realize the frequency lock of laser instrument, the microwave signal of the 3.4GHz of frequency synthesizer 22 outputs is sent into the electric current high frequency modulated end of vertical-cavity-face emitting semiconductor laser 15 it is modulated, the modulation signal of 10KHz is sent into the electric current low frequency modulations end of vertical-cavity-face emitting semiconductor laser 15 and the reference input of signal receiving processor 19 simultaneously, 3.4GHz microwave signal laser is carried out depth modulation, the frequency of two sidebands of modulation back laser differs 6.8GHz, just in time be rubidium (
87Rb) ground state level of atom interval, the current controling end that the error signal that obtains after the signal process signal receiving processor 19 processing demodulation of photodetector 18 is sent into vertical-cavity-face emitting semiconductor laser 15 carries out frequency stabilization to this laser instrument.
Realize the closed loop locking of atomic clock, the radiofrequency signal (10MHz) of voltage controlled oscillator 21 outputs is sent into microwave cavity 1 through the output signal (6.8GHz) that obtains behind the frequency synthesizer 22, the output signal of microwave power detector 24 is sent into signal receiving processor 19, differential signal control voltage controlled oscillator 21 after the processing demodulation is realized the closed loop locking.The stable 10MHz signal 20 of voltage controlled oscillator 21 is as the time and frequency standard of atomic clock, the i.e. realization of atomic clock.
The realization of physical process with
87Rb is that actuating medium (in fact being suitable for all alkali metal atoms) is example, and level structure figure as shown in Figure 3.Shown in Fig. 3 (a), cool off light and return the D2 line that pump light is selected the rubidium atom for use, relevant population number imprison light is selected the D1 line of rubidium atom for use, and Fig. 3 (b) is hyperfine structure division in magnetic field behind the elimination degeneracy of rubidium atom, and cooling and imprison light frequency are adjusted to 5S
1/2, F=2 → 5P
3/2, about two natural widths of the red off resonance in F '=3 are returned the pump light frequency and are adjusted to 5S
1/2, F=1 → 5
3/2F '=2 Near resonance oscillatings, open the electric current of the quadrupole coil of magneto-optic trap, the magnetic field gradient that quadrupole coil produces is about every centimetre 10 Gauss, and under the acting in conjunction of cooling imprison light and four utmost point magnetic wells, the cold atom group of a strip 14 axially forms along microwave cavity 1, after turning off quadripolar magnetic field cooling light intensity and frequency are scanned, do the cooling of polarization gradient, turn off cooling imprison light then, the temperature of cold atom is in little K magnitude at this moment.
After 10MHz signal 20 process frequency synthesizers 22 frequencys multiplication of stable VCXO 21 outputs, the electric current high frequency modulated end of the microwave signal input vertical-cavity-face emitting semiconductor laser 15 of the 3.4GHz of output, produce two sidebands, its sideband frequency ω after the depth modulation
1, ω
2Respectively with 5S
1/2, F=1 → 5P
1/2, F '=2 and 5S
1/2, F=2 → 5P
1/2, F '=2 resonance, the scanning microwave frequency, atom is prepared in the stack attitude of two ground state when satisfying the two-photon resonance condition, and the coherent optical radiation field is passed through the cold atom assemblage pellucidly, photodetector 18 signal maximums, promptly relevant population number imprison signal.The 10KHz signal of frequency synthesizer 22 outputs carries out low frequency modulations to the electric current of vertical-cavity-face emitting semiconductor laser 15, the reference input of while input signal receiving processor 19, relevant population number imprison signal by the modulation of 10KHz signal after through sending into signal receiving processor 19 behind photodetector 18 absorbing detections, signal after the processing demodulation is sent into the current controling end of vertical-cavity-face emitting semiconductor laser 15, thereby it is carried out frequency stabilization.
Helmholtz coils 6 guarantees to produce a constant magnetic field, i.e. C field along the direction of propagation of vertical-cavity-face emitting semiconductor laser 15 light beams at microwave cavity 1 on axially.The sideband frequency ω of frequency synthesizer 22 modulation vertical-cavity-face emitting semiconductor lasers 15
1With 5S
1/2, F=1, m
F=0 → 5P
1/2, F '=2, m
F=0 resonance, ω
2With 5S
1/2, F=2, m
F=0 → 5P
1/2, F '=2, m
F=0 resonance, the 6.8GHz microwave signal of frequency synthesizer 22 outputs is sent into microwave cavity 1 behind quarter-wave plate 26, in Λ type three-lever system, as microwave frequency and 5S
1/2, F=1, m
F=0 → 5P
1/2, F '=2, m
F=0 and 5S
1/2, F=2, m
F=0 → 5P1/2, F '=2, m
FProduce relevant microwave radiation signal during=0 resonance, the signal of microwave power detector 24 is sent into signal receiving processor 19, and the deviation correcting signal after the processing demodulation locks VCXO 21.
After finishing above-mentioned steps the frequency of vertical-cavity-face emitting semiconductor laser 15 and the frequency of VCXO 21 are carried out synchronous locking, the 10MHz signal 20 of stable voltage controlled oscillator 21 is the frequency reference signal of atomic clock.
Above technical scheme can realize that a kind of compact conformation, volume are little, stability and the good and practical coherent maser radiation cold atomic clock of accuracy.
Claims (1)
1, a kind of coherent maser radiation cold atomic clock, it comprises vacuum system, field coil, semiconductor laser (10), magnetic field shielding system (8), vertical-cavity-face emitting semiconductor laser (15), VCXO (21), frequency synthesizer (22), signal receiving processor (19), photodetector (18) and microwave power receptacle (24), it is characterized in that: the vacuum system shielding comprises ionic pump (3) in magnetic field shielding system (8), vacuum pipeline (2), microwave cavity (1), first to the 3rd quartz window (4a, 4b, 4c), ionic pump (3) links to each other with vacuum pipeline (2), vacuum pipeline (2) links to each other with microwave cavity (1), first quartz window (4a) is arranged on the vacuum pipeline (2), second quartz window (4b) and the 3rd quartz window (4c) are arranged on the microwave cavity (1), microwave cavity (1), a pair of anti-Helmholtz coils (5), a pair of Helmholtz coils (6) and a pair of square coil (7) are placed in the magnetic field shielding system (8), three catoptron (9a, 9b, 9c) be fixed in the microwave cavity (1), its angle and microwave cavity tangent plane form 25 ° angle, a pair of anti-Helmholtz coils (5) and a pair of Helmholtz coils (6) are fixed on the axial direction of microwave cavity (1), a pair of square coil (7) is fixed on microwave cavity (1) in the radial direction, semiconductor laser (10) comprises the laser of two frequencies, be respectively applied for imprison light and return pump light light beam, imprison light and time pump light are simultaneously through two beam splitters (11,16), catoptron (9a, 9b, 9c) and the 3rd quartz window (4c) after, form three couples of orthogonal laser (13a-13b, 13c-13d, 13e-13f), under the acting in conjunction of these three pairs of orthogonal laser and a pair of anti-Helmholtz coils (6) and a pair of square coil (7), form strip magneto-optic trap, the relevant population number imprison of vertical-cavity-face emitting semiconductor laser (15) output laser beam (17), VCXO (21) links to each other with frequency synthesizer (22), frequency synthesizer (22) respectively with signal receiving processor (19), vertical-cavity-face emitting semiconductor laser (15) links to each other with microwave cavity (1), photodetector (18) links to each other with signal receiving processor (19) respectively with microwave power receiver (24), signal receiving processor (19) links to each other with vertical-cavity-face emitting semiconductor laser (15) with VCXO (21) respectively, photodetector (18), signal receiving processor (19) and vertical-cavity-face emitting semiconductor laser (15) are formed laser frequency stabilization loop, VCXO (21), frequency synthesizer (22), microwave power receiver (24), signal receiving processor (19) composed atom clock closed circuit.
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