EP1730608B1 - Verfahren zur modulation eines atomuhrsignals mit coherent population trapping und entsprechende atomuhr - Google Patents

Verfahren zur modulation eines atomuhrsignals mit coherent population trapping und entsprechende atomuhr Download PDF

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EP1730608B1
EP1730608B1 EP05744396A EP05744396A EP1730608B1 EP 1730608 B1 EP1730608 B1 EP 1730608B1 EP 05744396 A EP05744396 A EP 05744396A EP 05744396 A EP05744396 A EP 05744396A EP 1730608 B1 EP1730608 B1 EP 1730608B1
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pulse
atomic clock
response signal
atomic
intensity
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French (fr)
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EP1730608A1 (de
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Noël DIMARCQ
Stéphane GUERANDEL
Thomas Zanon
David Holleville
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Centre National de la Recherche Scientifique CNRS
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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
    • 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
    • G04F5/145—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks using Coherent Population Trapping

Definitions

  • CPT clocks for "Coherent Population Trapping” Atomic clocks with consistent population trapping, designated CPT clocks for "Coherent Population Trapping" are known from the state of the art.
  • the atomic clocks use an interaction medium, generally formed by cesium or rubidium atoms excited by a radio-electric signal generated by a local oscillator LO and a synthesizer S at an excitation frequency and formed by a signal microwave at 6.8 GHz respectively 9.2 GHz for rubidium and cesium.
  • the atoms of the interaction medium are excited between two energy levels e and f represented in figure 1b .
  • This mode of excitation is called Rabi's interrogation mode if the interaction is continuous and Ramsey interrogation mode if the interrogation is based on two short interactions separated by a dead time.
  • the response signal from the interaction has an amplitude depending on the tuning to the resonance of the excitation signal. Detection of the response signal can be performed by optical absorption, magnetic selection, optical fluorescence or magnetic detection.
  • a system for controlling the local oscillator from the response signal makes it possible to obtain at the output of this oscillator a periodic signal S u , having qualities of accuracy and frequency stability comparable to those of the resonance frequency. e ⁇ f.
  • the CPT clocks also use an interaction medium illuminated by two laser waves and implement a continuous interrogation mode.
  • the interaction medium consisting of sodium is spatially separated into two distinct interaction zones, separated by a distance of 30 cm.
  • the laser beams make it possible to generate a Raman transition resonance at 1 772 MHz, the central fringe of the Ramsey fringe pattern being reduced to a width of 650 Hz, thanks to an interaction produced in the interaction zones.
  • CPT type atomic clocks implement a continuous mode interrogation, by means of two coherent laser waves in phase.
  • Each laser wave is quasi-resonant with an optical transition of the atoms 2 ⁇ e and 2 ⁇ f and the difference between the frequencies of the two waves is close to the atomic reference frequency f ⁇ e.
  • the atoms of the interaction medium are trapped in a coherent superposition of the states f and e corresponding to a black state.
  • the coherent superposition of atomic states is also associated with a magnetization generating an electromagnetic wave oscillating at the frequency of the transition e ⁇ f in the microwave domain.
  • Fluorescence absorption or emission is minimal and the field of the electromagnetic wave emitted has a maximum amplitude at resonance.
  • the atomic clock signal corresponds to the variation of the amplitude of the signal detected by absorption, fluorescence or microwave emission, as a function of the value of the frequency difference of the laser waves.
  • the above-mentioned low amplitude atomic clock signals are detected under degraded signal-to-noise ratio conditions, which again results in a degradation of the frequency stability of the atomic clock.
  • the object of the present invention is to remedy the technical problem of the optical saturation of the interaction media of the atomic clocks, in particular CPT or other clocks, while maintaining non-degraded signal-to-noise ratio conditions.
  • Another object of the present invention is, furthermore, through a specific processing of the response signal generated by the interrogation of the interaction medium in the current CPT atomic clocks, to obtain an increase in the contrast of the fringes of the interference in Ramsey mode and a decrease in slow amplitude variations or drifts of the atomic clock signal, generated in particular by the irreducible fluctuations of the operating parameters, such as the frequency and the amplitude of the interrogation lasers of the interaction medium.
  • Another object of the invention is, finally, the implementation of a method for generating a clock signal CPT and a corresponding clock CPT allowing a miniaturization of this type of clock for the production clocks in which the interaction cell does not exceed a volume of a few mm 3 .
  • the method for generating a coherent population-entrapped atomic clock signal uses a first and a second phase-coherent laser wave, each substantially resonant with an optical transition of the atomic atoms. an interaction medium.
  • the coherent superposition of the atomic states corresponding to the coherent trapping of the atomic population makes it possible to generate a response signal exhibiting a amplitude resonant at the resonance and representative of the atomic clock signal corresponding to the amplitude variation of the detected signal as a function of the value of the frequency difference of the first and second in-phase coherent laser waves.
  • the response signal is detected and superimposed by linear combination of the response signal generated during this current pulse and at least one pulse preceding this current pulse, to generate a resulting compensated atomic clock signal, the spectral width of which is minimized.
  • the pulsed interrogation atomic clock which is the subject of the present invention, comprises at least one interrogation optical module making it possible to generate a coherent first and second phase-coherent laser beam, each substantially resonant with an optical transition of the atomic atoms.
  • an interaction medium an interaction cell comprising this interaction medium, illuminated in operation by the first and second coherent laser beams in phase, to generate a response signal having an extreme amplitude at resonance and corresponding to the amplitude variation of the detected signal as a function of the frequency difference of the first and second coherent laser beams in phase and a detection module of this response signal adapted to the wavelength and amplitude of the response signal .
  • a pulse modulating block of the intensity of the first and second laser beams between a high level and a low intensity level is placed on the path of the first and second laser beams, upstream of the interaction cell, to synchronously generate a first and a second pulsed laser beam.
  • the interaction between the first respectively the second laser beam and the interaction medium is substantially limited to the duration of each successive pulse corresponding to a high intensity level and the signal of The response generated during a current pulse depends on the atomic state generated during at least one pulse preceding this current pulse and the evolution of that atomic state during the low intensity period between these pulses.
  • the detection module comprises a summation module by linear combination of the response signal generated during this current pulse and the response signal generated during at least one pulse preceding this current pulse.
  • the summation module by linear combination makes it possible to generate a resulting compensated atomic clock signal whose spectral width is minimized.
  • the method and the atomic clock with coherent trapping of population objects of the present invention find application to the industrial implementation of timepieces or frequency reference embedded very small footprint, used in particular in space applications.
  • the method which is the subject of the present invention is implemented from a first laser wave L 1 and a second laser wave L 2 consistent in phase.
  • each of the aforementioned laser waves is substantially in resonance with an optical transition of the atoms of an interaction medium, the laser waves L 1 and L 2 being deemed to be emitted at a frequency f 1 and f 2 and at their wavelength corresponding in vacuum or air, the frequency difference of the aforementioned laser waves being noted ⁇ f 12 .
  • the laser waves L1 and L2 are polarized either circularly or linearly orthogonally.
  • the coherent superposition of the atomic states corresponding to the coherent trapping of the atomic population as represented in FIG. figure 1b generates a response signal in the microwave domain having a amplitude at resonance and representative of the atomic clock signal corresponding to the amplitude variation of the detected response signal as a function of the value of the frequency difference ⁇ f 12 of the first and second coherent laser waves in phase L 1 and L 2 .
  • the mode of interaction of the first and second waves with the interaction medium corresponds to the continuous interaction mode known from the state of the art from the physical point of view.
  • this consists at least in a step A of sequentially pulsing modulating the intensity of the first and second laser waves L 1 , L 2 according to a given form factor, between a high level and a low intensity level.
  • the laser waves L 1 and L 2 are represented which are synchronously modulated by successive pulses, the successive pulses being deemed to have a rank r, r-1, ..., rp with respect to a growing time scale t.
  • the current pulse is deemed to have a rank r, the pulse immediately preceding this current pulse rank r-1 and successive previous pulses being deemed to have an earlier rank successively up to r-p.
  • the interaction between the first and second laser waves L 1 , L 2 and in particular the pulsed shape thereof and the interaction medium is substantially limited to the duration of each successive pulse S r , S r-1 to S rp corresponding to a high level of intensity.
  • the response signal generated during a current pulse depends on the atomic state generated during at least one pulse preceding this current pulse, that is to say the previous pulses of rank r-1 to rp and the evolution of this atomic state during the duration of low level of intensity separating the aforementioned pulses.
  • the object process of the invention consists particularly remarkably to detect in step B and superimpose by linear combination in step C the response signal generated during the current pulse response signal noted S r of rank r corresponding to that of the illumination pulse of the same rank and at least one pulse preceding this current pulse to generate the resulting compensated atomic clock signal, whose spectral width is minimized.
  • step B the detection operation is represented in step B, the response signal being deemed to consist of the corresponding response signal S r of rank r and the successive successive response signals S r-1 to S rp .
  • step C of the figure 2a The linear combination superposition operation is represented in step C of the figure 2a and illustrated by the following linear combination formula:
  • S HC represents the resulting compensated atomic clock signal obtained by the aforementioned linear combination C k designating a positive and / or negative weighting coefficient applied to each successive response signal pulse S k .
  • the pulse modulation process of the laser waves L 1 and L 2 is advantageously carried out by pulse train, the frequency of the modulation pulses being between 0.2 Hz and 10 4 Hz.
  • the high intensity level of each pulse for a given pulse train has a duration h and the low intensity level has a duration b.
  • the frequency range of the modulated laser wave pulses represented in point 1 of the figure 2b and finally response signal of successive rows r, r-1, rp is given by the value 1 / h + b for the different values of h and b and the form factor defined by the value h / h + b is then between 10 -6 and 10 -1 .
  • pulses I of modulated laser waves represented in point 1) can be obtained by an electronic control signal having exactly the temporal and / or frequency characteristics of those represented in point 1) of FIG. figure 2b above.
  • duration interval b separating the current pulse of rank r from the pulse preceding this current pulse or any previous pulse of rank r-1 to rp in a pulse train of modulation, one indicates that this duration b is less than the life time of the hyperfine coherence existing between the two clock levels.
  • the two clock levels concerned are the levels e and f which determine the frequency of the resulting atomic clock signal and that this life time depends essentially on the interaction medium considered.
  • One of the remarkable aspects of the process that is the subject of the present invention is in particular that the latter is capable of being implemented from interaction media consisting either of atomic populations the cells contained by cold atoms and, in particular, cooled by laser.
  • the interrogation process is advantageously constituted by a Ramsey interrogation mode with at least two pulses.
  • the thermal atoms are delivered in the form of steam or jet.
  • Obtaining the laser-cooled atoms involves interacting the thermal atoms with correctly tuned laser waves with respect to optical transitions of the atoms.
  • the radiation pressure induced by the laser waves makes it possible to rapidly reduce the kinetic energy of the atoms.
  • samples of cooled atoms are obtained with very low erratic speeds, of the order of 1 cm / s, corresponding to a temperature of 10 -6 K, much lower than that of thermal atoms, of the order of a few hundred meters per second at a temperature of 300 K.
  • the kinetic energy of the atoms or the variation of kinetic energy thereof is proportional to the temperature decrease from the initial value 300 K to 10 -6 K, the coefficient of proportionality depending on the Boltzmann constant.
  • the aforementioned detection process is advantageously chosen from the group of detection processes comprising optical absorption, Optical fluorescence, microwave detection as a function of the frequency of the interrogation signal.
  • the method which is the subject of the present invention can be implemented in many situations taking into account the nature of the interaction medium chosen, the interrogation mode being however preferentially the Ramsey interrogation mode with at least two pulses, as mentioned previously in the description.
  • the detection processes are then the detection processes by optical absorption, optical fluorescence, microwave detection as a function of the frequency of the aforementioned interrogation signal.
  • the table below establishes the type of atomic clock capable of implementing the method that is the subject of the present invention, indicating the atomic source used to enable the implementation of the method, the interrogation method or mode and the process. detecting the corresponding clock signal.
  • TYPE OF ATOMIC CLOCK ATOMIC SOURCE INTERROGATION MODE CLOCK SIGNAL DETECTION CPT coherent trapping of population on thermal atoms in cells
  • Optical interrogation clock transition in the microwave domain
  • Continuous in existing devices Pulsed interrogation in this type of clock
  • Optical absorption or microwave detection CPT coherent trapping of population on cold atoms
  • Optical interrogation (clock transition in the microwave domain) Pulsed type query.
  • such a clock comprises, in an optical section SO, an interrogation optical module 1 for generating a coherent first and second laser beam in the L 1 , L 2 phase.
  • each of the aforementioned laser beams is substantially in resonance with an optical transition of the atoms of an interaction medium.
  • the pulsed interrogation atomic clock further comprises an interaction cell 3 comprising the aforementioned interaction medium.
  • interaction cell 3 By notion of interaction cell 3, it is indicated that the interaction cell can be constituted in a conventional manner by a transparent envelope to the laser beam L 1 , L 2 and of course, by any device generating the interaction medium, c i.e. thermal atoms and / or laser cooled.
  • the interrogation module 1 generates the two laser beams L 1 and L 2 whose difference in frequency is equal to the resonance frequency, the microwave frequency at 9.2 GHz for cesium and 6.8 GHz for rubidium. for example.
  • the frequencies of the laser diodes are in the neighborhood of 852 nm for the D 2 line and 894 nm for the D 1 line .
  • the aforementioned laser lines can be used for a CPT interaction as described above in the description.
  • the transitions of the line D 1 appear more interesting because they make it possible to reduce, on the one hand, the losses of atoms due to leakage on adjacent transitions, and, on the other hand, light shifts.
  • Different processes can be implemented to generate two radiations, that is to say the laser beams L 1 and L 2 , which induce the coherent entrapment of the atomic population of the interaction medium.
  • the frequency difference between the laser beams L 1 and L 2 is equal to the clock frequency, that is to say the frequency of the atomic clock signal.
  • the phase difference between the phase of the laser beams L 1 and L 2 must have fluctuations as low as possible in order to avoid any destruction of the interference phenomenon.
  • the required transmit power for laser beams is in the milliwatt range.
  • the interrogation optics can be made from a single laser source to which a frequency modulation at several GHz of the modulation type is applied. sidebands, the distance between the sidebands corresponding to the clock frequency. The two previously mentioned lines are thus provided with phase coherence as good as that of the modulation signal.
  • the two lines or laser beams L 1 and L 2 are then physically superimposed in a conventional manner so that the latter follow the same optical path and are subjected to the same successive phase shifts until they are applied to the interaction medium.
  • interaction cell 3 it is indicated that it can be implemented from a pyrex or quartz enclosure.
  • buffer gases may be added to eliminate Doppler line broadening by placing in the Lamb-Dicke regime.
  • the magnetic and thermal environment is tightly controlled to avoid any variation in frequency shift that would affect the accuracy and long-term stability of the atomic clock thus formed.
  • the pulsed interrogation atomic clock comprises, in a detection section SD, also a module 4 for detecting the response signal, the response signal being defined as the signal delivered by the interaction medium of the cell 3 after illumination of the interaction medium by laser beams L 1 and L 2 .
  • the detection module 4 is of course adapted to the wavelength and the amplitude of the response signal to deliver an electronic version of the response signal.
  • the module 4 for detecting the response signal may consist of modules implementing the detection processes as described in the above-mentioned table.
  • the pulsed interrogation atomic clock object of the present invention comprises a module 2 pulse modulation of the intensity of the first and second laser beams L 1 and L 2 between a high level and a low level of intensity.
  • the modulation module 2 is placed in the optical section SO on the path of the first and second laser beam upstream of the interaction cell 3 for generating in synchronism a first and a second pulsed laser beam for illuminating the interaction medium contained in the cell 3, according to the figure 2a .
  • the interaction between the aforementioned laser beams and the interaction medium is substantially limited to the duration of each corresponding successive pulse. at a high level of intensity.
  • the response signal generated during a current pulse of rank r for example depends on the atomic state generated during at least one pulse preceding this current pulse, that is to say pulses of rank r-1 to rp previously mentioned in the description, and, of course, the evolution of this atomic state during the duration of low intensity energy level separating these pulses.
  • the detection module of the response signal 4 can be followed by a processing module 5, the processing module receiving the electronic version of the response signal and performing summation processing by linear combination of the response signal generated during the first response signal. current pulse and during at least one pulse preceding this current pulse, that is to say during the successive previous pulses.
  • the linear combination processing module 5 thus makes it possible to generate a resulting compensated atomic clock signal whose spectral width is minimized and to construct a correction signal S c making it possible to drive the frequency of a local oscillator 6.
  • the processing module 5 in fact delivers the correction signal Sc to the module 6 implanted in an analog section SA and constituted for example by a local oscillator LO and a synthesizer S delivering, on the one hand, a periodic signal servocontrolled in frequency S u , for use as a frequency reference for an external user, and, secondly, a control signal S co of the interrogation optical module 1.
  • This control signal S co may for example consist of a frequency reference for performing the control of the modulation process in lateral bands previously mentioned in the description. to obtain the two laser beams L 1 and L 2 , from a single laser source, for example. It is indicated that the above-mentioned control signal S co may also make it possible to provide control of the wavelength and / or the frequency of the laser beams L 1 and L 2 at the chosen value.
  • the pulsed interrogation atomic clock object of the present invention, is provided with a control unit 7 which can be constituted by a microcomputer connected by a bus link to all the modules such as the module of pulse modulation 2, the module 4 for detecting the response signal, and of course the processing module 5 and the module 6 acting as local oscillator LO and / or synthesizer S.
  • a control unit 7 which can be constituted by a microcomputer connected by a bus link to all the modules such as the module of pulse modulation 2, the module 4 for detecting the response signal, and of course the processing module 5 and the module 6 acting as local oscillator LO and / or synthesizer S.
  • control unit 7 makes it possible to ensure the synchronization of all the aforementioned modules as well as the control of the generated modulation pulse trains, from an electronic control signal, for example, developed by the control unit 7, to control the modulation module 2.
  • L 2 indicates that the latter may be constituted by an acousto-optical modulator, an electro-optical modulator or finally by any other component for modulating the intensity of a light signal whose response time is short enough to ensure such modulation.
  • the low level of intensity corresponds to a substantially zero intensity of each of the laser beams or the radio frequency signal, these being totally absorbed by the modulation module 2 previously mentioned.
  • processing module 5 receives the response signal in the form of an electronic signal delivered by the detection module 4.
  • the processing module 5 can, as represented in FIG. figure 4a , advantageously comprising a sampling module 50 of the response signal generated during the interaction of the current pulse and at least one pulse preceding this current pulse, the aforementioned sampling module 50 being triggered in synchronism with the control of the module 2 for modulating the laser beams L 1 and L 2 .
  • the sampling module 50 is preferably followed by a module 51 for storing the sampled values of the response signal generated during the interaction of each of the aforementioned pulses.
  • the storage module 51 can be followed by a module 52 making it possible to calculate a linear combination of the stored sampled values making it possible to generate the compensated atomic clock signal S HC previously mentioned in the description.
  • a module 53 formed for example by an integrator makes it possible to deliver the correction signal S c to the module 6 constituted by the local oscillator LO and the synthesizer S, for example.
  • the synthesizer S makes it possible to generate a microwave signal whose frequency is close to the resonant frequency of the transition e ⁇ f.
  • control unit 7 may advantageously be constituted by a workstation or a microcomputer comprising a control program of the assembly, so as to ensure the synchronization of the modulation module 2, the detection module 4 of the response signal from the processing module 5 previously described in connection with the figure 4a and, of course, the module 6 constituted by the local oscillator and the synthesizer previously described.
  • control unit 7 may advantageously be programmed to ensure, by means of control software, a reading of the sampled values stored in the storage module 51 at given times. .
  • control unit 7 can then comprise a program for sorting the sampled values stored for for each of the pulses S r and S rp, determining the maximum and / or minimum values of these sampled values for each of the aforementioned successive pulses.
  • a treatment process may advantageously consist, as represented in point 2 of FIG. figure 4b for the current pulse S r of rank r, to determine the sampled value of this pulse which has the maximum value, this maximum value being denoted M r then for the successive pulses of prior rank r-1 to rp, to be determined in each of these the minimum of the corresponding sampled values in its successive pulses.
  • the corresponding minima are denoted m r-1 for the previous impulse immediately preceding the current impulse, this anterior impulse being of rank r-1, then the successive values m r-2 to m rp for previous previous impulses of rank r-2 to rp.
  • the linear combination of the sampled values can then consist in adding the maximum of the sampled values for the current rank pulse. r and to subtract the successive minimum values of the previous pulses of rank r-1 to rp, as represented on the figure 4b , or an average value thereof.
  • the sorting program can then perform the sorting with respect to the origin of each of the pulses, these origins being noted successively or, O r-1 , O rp .
  • the maximum M r of the current pulse of rank r makes it possible to obtain the maximum amplitude value for the detected response signal while the subtraction of the successive sampled values representative of the local minima for the latter, on the contrary, makes it possible to subtract a sampled value representative of the drifts and perturbations introduced by the interaction medium contained in the cell 3, in order to obtain a compensated atomic clock signal whose spectral width is thus minimized and whose contrast can to be significantly improved, thanks to the removal of continuous or slowly variable components representative of the drift of the entire system.
  • the modules 51, 52 and 53 can be replaced by a programmed dedicated signal processor. for this purpose.
  • the width of the oscillation line obtained for the clock signal, width to 3dB with respect to the The maximum amplitude at the top of the oscillation is a few kHz for a central frequency of the order of a few GHz.
  • Such a linewidth is too important to be compatible with the use of such atomic clocks as a reference clock. This can be explained by the fact that in the absence of a buffer gas, the atoms of the interaction medium are subjected to an excessive rapid erratic displacement which widens the resonance phenomenon by Doppler effect and limitation of the transit time and finally, the quality of the radio-electric resonator thus formed.
  • ⁇ f TT varies as 1 / T where T denotes the interaction time between an atom and the laser waves.
  • the figure 4c illustrates the mode of implementation of the method that is the subject of the present invention by virtue of a pulsed interrogation atomic clock in which the interaction medium is constituted by thermal atoms of cesium in the presence of a buffer gas, formed by nitrogen. It represents the amplitude of compensated clock signal S HC as a function of the disagreement of the difference in the frequencies ⁇ f 12 of the two laser waves.
  • the x-axis of the figure 4c is graduated in kHz with respect to a 0 value origin of the Raman mismatch.
  • the distance ⁇ represents the disagreement introduced due to the presence of the buffer gas.
  • This frequency bias can be reduced by using two buffer gases, nitrogen and argon for example, inducing collisional movements of opposite sign.
  • the width of the oscillations remains as low as 25 Hz thanks to the implementation of the treatment and, of course, the pulse modulation of the laser beams L 1 and L 2 used.
  • the interaction medium is constituted by atoms cooled by laser, the speed of the atoms is reduced under the conditions previously mentioned in the description, that is to say at erratic speeds about 1000 times lower than those of thermal atoms.
  • the rubidium atom appears more interesting than the cesium atom because the collisional displacement is at least 50 times lower.
  • the interrogation process is carried out in accordance with the method that is the subject of the present invention, that is to say by pulsed interrogation, it is then possible to very significantly reduce the contribution of the saturation effect. while continuing to detect the signals of sufficient intensity, that is to say with a satisfactory signal-to-noise ratio.

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Claims (10)

  1. Verfahren zum Erzeugen eines Atomuhrsignals mit "Coherent Population Trapping" (kohärentes Besetzungs-Einfangen) aus einer ersten und einer zweiten phasenkohärenten Laserwelle, die jeweils im Wesentlichen in Resonanz mit einem optischen Übergang der Atome eines Interaktionsmediums sind, wobei die dem kohärenten Einfangen einer Atombesetzung entsprechende kohärente Überlagerung der Atomzustände ein Antwortsignal erzeugt, das eine Amplitude aufweist, die extremal zu der Resonanz und für das Atomuhrsignal repräsentativ ist, das der Amplitudenvariation des Signals entspricht, das in Abhängigkeit von dem Wert des Frequenzunterschiedes der ersten und der zweiten phasenkohärenten Laserwelle detektiert wird, dadurch gekennzeichnet, dass es mindestens aus folgendem besteht:
    - synchrones Modulieren mittels aufeinanderfolgender Impulse der Stärke der ersten und der zweiten Laserwelle gemäß einem bestimmten Formfaktor zwischen einem hohen und einem niedrigen Stärkepegel, wobei die Interaktion zwischen der ersten beziehungsweise der zweiten Laserwelle und dem Interaktionsmedium im Wesentlichen auf die Dauer jedes nachfolgenden Impulses beschränkt ist, der einem hohen Stärkepegel entspricht, wobei das während eines aktuellen Impulses erzeugte Antwortsignal von dem Atomzustand, der während mindestens eines dem aktuellen Impuls vorangehenden Impulses erzeugt wurde, und von der Entwicklung des Atomzustandes während der die Impulse trennenden Dauer des niedrigen Stärkepegels abhängt,
    - Detektieren und Überlagern mittels Linearkombination des während des aktuellen Impulses und mindestens eines dem aktuellen Impuls vorangehenden Impulses erzeugten Antwortsignals zum Erzeugen eines kompensierten Ergebnis-Atomuhrsignals, dessen spektrale Breite minimalisiert ist.
  2. Verfahren gemäß Anspruch 1, dadurch gekennzeichnet, dass die Impulsmodulation mittels Impulsfolgen durchgeführt wird, wobei die Modulationsimpuls-Frequenz zwischen 0,2 Hz und 104 Hz liegt.
  3. Verfahren gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Modulationsimpulse einen Formfaktor zwischen 10-6 und 10-1 aufweisen.
  4. Verfahren gemäß einem der Ansprüche 1 bis 3,
    dadurch gekennzeichnet, dass die Dauer des niedrigen Stärkepegels, die den aktuellen Impuls von dem diesem aktuellen Impuls vorangehenden Impuls trennt, kürzer als die Lebensdauer der hyperfeinen Kohärenz ist, die zwischen zwei Taktpegeln vorhanden ist.
  5. Verfahren gemäß einem der Ansprüche 1 bis 4,
    dadurch gekennzeichnet, dass das Interaktionsmedium aus einer Mehrzahl von thermischen oder lasergekühlten Atomen gebildet wird.
  6. Verfahren gemäß einem der Ansprüche 1 bis 5,
    dadurch gekennzeichnet, dass der Schritt, der aus dem Detektieren des Taktsignals besteht, in Abhängigkeit von dem Frequenzunterschied der ersten und der zweiten phasenkohärenten Laserwelle als eines der Detektionsverfahren aus der Gruppe der Detektionsverfahren ausgewählt wird, die die optische Absorption, die optische Fluoreszenz und die Mikrowellendetektion aufweisen.
  7. Atomuhr mit gepulster Abfrage, die mindestens folgendes aufweist:
    - ein optisches Abfragemedium (1), welches das Erzeugen eines ersten und eines zweiten phasenkohärenten Laserstrahls (L1, L2) ermöglicht, von denen jeder mit einem optischen Übergang der Atome eines Interaktionsmediums (3) im Wesentlichen in Resonanz ist,
    - eine Interaktionszelle (3), die das Interaktionsmedium aufweist, das im Betrieb von dem ersten und dem zweiten phasenkohärenten Laserstrahl beleuchtet wird, zum Erzeugen eines Antwortsignals, das eine Amplitude aufweist, die zu der Resonanz extremal ist und der Amplitudenvariation des Signals entspricht, das in Abhängigkeit von dem Frequenzunterschied des ersten und des zweiten phasenkohärenten Laserstrahls detektiert wird,
    - Mittel zum Detektieren (4) des Antwortsignals, wobei die Detektionsmittel an die Wellenlänge und an die Amplitude des Antwortsignals angepasst sind,
    dadurch gekennzeichnet, dass die Atomuhr ferner aufweist:
    - Mittel zum Impulsmodulieren (2) der Stärke des ersten und des zweiten Laserstrahls zwischen einem hohen und einem niedrigen Stärkepegel, wobei die Modulationsmittel auf der Bahn des ersten und des zweiten Laserstrahls stromaufwärts von der Interaktionszelle (3) angeordnet sind, zum synchronen Erzeugen eines ersten und eines zweiten gepulsten Laserstrahls, wobei die Interaktion zwischen dem ersten beziehungsweise dem zweiten Laserstrahl und dem Interaktionsmedium im Wesentlichen auf die Dauer jedes nachfolgenden Impulses beschränkt ist, der einem hohen Stärkepegel entspricht, wobei das Antwortsignal, das während mindestens eines aktuellen Impulses erzeugt wird, von dem Atomzustand, der während mindestens eines dem aktuellen Impuls vorangehenden Impulses erzeugt wurde, und von der Entwicklung des Atomzustandes während der die Impulse voneinander trennenden Dauer des niedrigen Stärkepegels abhängt, und dass
    - die Detektionsmittel darüber hinaus Mittel zum Summieren (5) mittels Linearkombination des während des aktuellen Impulses erzeugten Antwortsignals und des während mindestens eines dem aktuellen Impuls vorangehenden Impulses erzeugten Antwortsignals aufweisen, wobei die Mittel zum Summieren mittels Linearkombination das Erzeugen eines kompensierten Ergebnis-Atomuhrsignals ermöglichen, dessen spektrale Breite minimalisiert ist.
  8. Atomuhr gemäß Anspruch 7, dadurch gekennzeichnet, dass die Mittel zum Impulsmodulieren der Stärke des ersten und des zweiten Laserstrahls zwischen einem hohen Stärkepegel und einem niedrigen Stärkepegel mindestens einen akustisch-optischen Modulator aufweisen.
  9. Atomuhr gemäß einem der Ansprüche 7 oder 8, dadurch gekennzeichnet, dass die Detektionsmittel ferner aufweisen:
    - Mittel zum Abtasten des Antwortsignals, das während der Interaktion des aktuellen Impulses und mindestens eines dem aktuellen Impuls vorangehenden Impulses erzeugt wird, und
    - Mittel zum Speichern der abgetasteten Werte des Antwortsignals, das während der Interaktion jedes der Impulse erzeugt wird.
  10. Atomuhr gemäß Anspruch 9, dadurch gekennzeichnet, dass die Detektionsmittel ferner aufweisen:
    - Mittel zum Auslesen der abgetasteten Werte zu bestimmten Zeitpunkten, die in den Speichermitteln gespeichert sind, und
    - Mittel zum Berechnen einer Linearkombination der gespeicherten abgetasteten Werte, die das Erzeugen des kompensierten Atomuhrsignals ermöglichen.
EP05744396A 2004-03-30 2005-03-29 Verfahren zur modulation eines atomuhrsignals mit coherent population trapping und entsprechende atomuhr Not-in-force EP1730608B1 (de)

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FR0403289A FR2868558B1 (fr) 2004-03-30 2004-03-30 Procede de generation d'un signal d'horloge atomique a piegeage coherent de population et horloge atomique correspondante
PCT/FR2005/000754 WO2005101141A1 (fr) 2004-03-30 2005-03-29 Procédé de génération d'un signal d'horloge atomique a piégeage cohérent de population et horloge atomique correspondante

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JP2007530965A (ja) 2007-11-01
US20070200643A1 (en) 2007-08-30
ATE508396T1 (de) 2011-05-15
FR2868558B1 (fr) 2006-06-30
US7501906B2 (en) 2009-03-10
WO2005101141A1 (fr) 2005-10-27
FR2868558A1 (fr) 2005-10-07
JP4801044B2 (ja) 2011-10-26
EP1730608A1 (de) 2006-12-13
DE602005027826D1 (de) 2011-06-16
CN100587629C (zh) 2010-02-03

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