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European Frequency and Time Forum

Evaluation of the CPT pseudo-resonance scheme for all-optical 87Rb frequency standard

Georgy A. Kazakov, Evelina Breschi, Boris G. Matisov, I. E. Mazets, C. Schori, C. Affolderbach, J. Vernotte, G. Mileti

Published Mar 27, 2006• 1 citation
OpenAlex

Abstract

We investigate a novel approach to all-optical frequency standards, based on a combination of the coherent population trapping effect and signal discrimination at the maximum of absorption of the probe radiation. The physics underlying this approach is dark resonance splitting caused by interaction of the nuclear magnetic moment with an external magnetic field. Theoretically it has been shown that this approach under ideal conditions can lead to an important enhancement of the clock stability. Here we present an experimental evaluation of the scheme in view its future application in the domain of vapor-cell atomic clocks. The present results point out that high-performances short-term stability can be obtained only with a high spectral quality light source. In contrast, for our compact and low-consumption setup, the shot-noise limited short-term stability calculated is about 10-12τ-1/2, which is comparable to those presently measured for typical CPT-based atomic clocks.

Related papers

Pseudoresonance mechanism of all-optical frequency-standard operation

Georgy A. Kazakov, Boris G. Matisov, I. E. Mazets +2 more

We propose an approach to all-optical frequency standard design, based on a counterintuitive combination of the coherent population trapping effect and signal discrimination at the maximum of absorption for the probe radiation. The short-term stability of such a standard can achieve the level of ${10}^{\ensuremath{-}14}∕\sqrt{\ensuremath{\tau}}$. The physics beyond this approach is a dark resonance splitting caused by the interaction of the nuclear magnetic moment with the external magnetic field.

arXiv:quant-ph/0506167•Physical Review A•Dec 21, 2005•45 citations

Coherent population trapping resonance scheme of simultaneously noise suppression and multiple constructive interferences

Suping Qu, Yi Yin, Xianyang Lu

Traditional coherent population trapping (CPT) atomic clocks use single circularly polarized coherent multichromatic light to interact with atoms for preparing CPT dark states. While this configuration is simple, it suffers from the trap states and involves only the ±1st-order sidebands in the CPT resonance, excluding the carrier and other sidebands. This results in a lower CPT signal amplitude and higher laser noise, limiting the frequency stability of CPT atomic clocks. To address this issue, we developed and experimentally validated a scheme utilizing left- and right-circularly polarized light based on multiple coherent superpositions. This scheme significantly enhances the amplitude of the CPT resonance. Furthermore, by incorporating a Michelson interferometer, the polarization direction of the ±1st-order sidebands in the coherent multichromatic light is adjusted from parallel to perpendicular, enabling the filtering of one sideband to be detected while eliminating other unwanted sidebands and effectively suppressing laser noise. The results show that, under identical conditions, the short-term frequency stability of this method is theoretically improved by a factor of seven compared to the traditional circularly polarized light scheme, providing an effective pathway for the development of high-performance CPT atomic clocks.

Review of Scientific Instruments•Jun 1, 2026•0 citations

A coherent population trapping Cs vapor cell atomic clock based on push-pull optical pumping

Moustafa Abdel Hafiz, Rodolphe Boudot

This article reports on the characterization of a compact coherent-population-trapping (CPT) Cs vapor cell atomic clock using the push-pull optical pumping technique. This method allows to detect high-contrast CPT resonances on the 0-0 magnetic-field insensitive clock transition. The clock short-term fractional frequency stability is measured to be 3×10−13 τ−1/2 up to 100 s averaging time, in correct agreement with the signal-to-noise ratio limit. These results are among the best performances ever reported for a CPT-based clock. The noise budget is detailed. A preliminary study is reported to evaluate limitations to the clock mid-term frequency stability. The clock performances are found to be presently mainly limited in the mid-term by laser power effects.

Journal of Applied Physics•Sep 28, 2015•49 citations

Feasibility toward a compact high performance coherent population trapping clock

Peter Yun, François Tricot, Emeric de Clercq +4 more

We demonstrate a vapor-cell atomic-clock prototype based on a continuous-wave interrogation and double-modulation coherent population trapping (DM-CPT) technique. The DM-CPT technique uses a synchronous modulation of polarization and the relative phase of a bichromatic laser beam in order to increase the number of atoms trapped in a dark state, i.e., a nonabsorbing state. The narrow resonance, observed in the transmission of a Cs vapor cell, is used as a narrow frequency discriminator in an atomic clock. A detailed characterization of the CPT resonance versus numerous parameters is reported. A short-term fractional-frequency stability of 3.2×10−13τ−1/2 up to a 100-s averaging time is measured. These performances are more than one order of magnitude better than industrial Rb clocks and are comparable to those of the best laboratory-prototype vapor-cell clocks. The noise-budget analysis shows that the short- and midterm frequency stability is mainly limited by the power fluctuations of the microwave used to generate the bichromatic laser. These preliminary results demonstrate that the DM-CPT technique is well suited for the development of a high-performance atomic clock, with the potential compact and robust setup due to its linear architecture. This clock could find future applications in industry, telecommunications, instrumentation, or global navigation satellite systems.

•Apr 14, 2019•0 citations

Investigations on continuous and pulsed interrogation for a CPT atomic clock

N. Castagna, Rodolphe Boudot, Stéphane Guérandel +3 more

We investigated the influence of some critical parameters and operating conditions such as cell temperature, laser intensity, and interrogation technique affecting the performances of a gas cell Cs frequency standard based on coherent population trapping (CPT). Thanks to an original experimental setup, the atoms can be trapped in the dark state and interrogated using continuous wave (CW) or pulsed coherent optical radiations. Using a double-lambda scheme, a signal contrast as high as 52% has been measured in the continuous regime for an optimum cell temperature of 35 degrees C. Compared with the conventional continuous CPT interrogation, the pulsed interrogation technique reduces the light shift by a factor of 300 and allowed it to reach high-frequency stability for higher laser intensities. The frequency stability has been measured to be 9 x 10(-13) for a 1 s integration time. Main noise contributions limiting the short-term and medium-term frequency stability are reviewed and estimated.

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control•Feb 1, 2009•60 citations

A novel absorption resonance for atomic clocks

David F. Phillips, Irina V. Novikova, Sergei A. Zibrov +5 more

We report an experimental study of an all-optical three-photon-absorption resonance (known as an "N-resonance") and discuss its potential application as an alternative to atomic clocks based on coherent population trapping (CPT). We present measurements of the N-resonance contrast, width and light shift for /sup 87/Rb under various conditions including both D/sub 1/ and D/sub 2/ optical transitions. Under conditions such that first-order light shifts cancel, we observe promising short-term frequency stability (/spl sim/ 1.5 /spl times/ 10/sup -11/ /spl tau//sub - 1/2 /) for an N-resonance on the Di transition of /sup 87/ Rb vapor.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Jan 18, 2006•2 citations
We investigate a novel approach to all-optical frequency standards, based on a combination of the coherent population trapping effect and signal discrimination at the maximum of absorption of the probe radiation. The physics underlying this approach is dark resonance splitting caused by interaction of the nuclear magnetic moment with an external magnetic field. Theoretically it has been shown that this approach under ideal conditions can lead to an important enhancement of the clock stability. Here we present an experimental evaluation of the scheme in view its future application in the domain of vapor-cell atomic clocks. The present results point out that high-performances short-term stability can be obtained only with a high spectral quality light source. In contrast, for our compact and low-consumption setup, the shot-noise limited short-term stability calculated is about 10-12τ-1/2, which is comparable to those presently measured for typical CPT-based atomic clocks.
We propose an approach to all-optical frequency standard design, based on a counterintuitive combination of the coherent population trapping effect and signal discrimination at the maximum of absorption for the probe radiation. The short-term stability of such a standard can achieve the level of ${10}^{\ensuremath{-}14}∕\sqrt{\ensuremath{\tau}}$. The physics beyond this approach is a dark resonance splitting caused by the interaction of the nuclear magnetic moment with the external magnetic field.
Traditional coherent population trapping (CPT) atomic clocks use single circularly polarized coherent multichromatic light to interact with atoms for preparing CPT dark states. While this configuration is simple, it suffers from the trap states and involves only the ±1st-order sidebands in the CPT resonance, excluding the carrier and other sidebands. This results in a lower CPT signal amplitude and higher laser noise, limiting the frequency stability of CPT atomic clocks. To address this issue, we developed and experimentally validated a scheme utilizing left- and right-circularly polarized light based on multiple coherent superpositions. This scheme significantly enhances the amplitude of the CPT resonance. Furthermore, by incorporating a Michelson interferometer, the polarization direction of the ±1st-order sidebands in the coherent multichromatic light is adjusted from parallel to perpendicular, enabling the filtering of one sideband to be detected while eliminating other unwanted sidebands and effectively suppressing laser noise. The results show that, under identical conditions, the short-term frequency stability of this method is theoretically improved by a factor of seven compared to the traditional circularly polarized light scheme, providing an effective pathway for the development of high-performance CPT atomic clocks.
This article reports on the characterization of a compact coherent-population-trapping (CPT) Cs vapor cell atomic clock using the push-pull optical pumping technique. This method allows to detect high-contrast CPT resonances on the 0-0 magnetic-field insensitive clock transition. The clock short-term fractional frequency stability is measured to be 3×10−13 τ−1/2 up to 100 s averaging time, in correct agreement with the signal-to-noise ratio limit. These results are among the best performances ever reported for a CPT-based clock. The noise budget is detailed. A preliminary study is reported to evaluate limitations to the clock mid-term frequency stability. The clock performances are found to be presently mainly limited in the mid-term by laser power effects.
We demonstrate a vapor-cell atomic-clock prototype based on a continuous-wave interrogation and double-modulation coherent population trapping (DM-CPT) technique. The DM-CPT technique uses a synchronous modulation of polarization and the relative phase of a bichromatic laser beam in order to increase the number of atoms trapped in a dark state, i.e., a nonabsorbing state. The narrow resonance, observed in the transmission of a Cs vapor cell, is used as a narrow frequency discriminator in an atomic clock. A detailed characterization of the CPT resonance versus numerous parameters is reported. A short-term fractional-frequency stability of 3.2×10−13τ−1/2 up to a 100-s averaging time is measured. These performances are more than one order of magnitude better than industrial Rb clocks and are comparable to those of the best laboratory-prototype vapor-cell clocks. The noise-budget analysis shows that the short- and midterm frequency stability is mainly limited by the power fluctuations of the microwave used to generate the bichromatic laser. These preliminary results demonstrate that the DM-CPT technique is well suited for the development of a high-performance atomic clock, with the potential compact and robust setup due to its linear architecture. This clock could find future applications in industry, telecommunications, instrumentation, or global navigation satellite systems.
We investigated the influence of some critical parameters and operating conditions such as cell temperature, laser intensity, and interrogation technique affecting the performances of a gas cell Cs frequency standard based on coherent population trapping (CPT). Thanks to an original experimental setup, the atoms can be trapped in the dark state and interrogated using continuous wave (CW) or pulsed coherent optical radiations. Using a double-lambda scheme, a signal contrast as high as 52% has been measured in the continuous regime for an optimum cell temperature of 35 degrees C. Compared with the conventional continuous CPT interrogation, the pulsed interrogation technique reduces the light shift by a factor of 300 and allowed it to reach high-frequency stability for higher laser intensities. The frequency stability has been measured to be 9 x 10(-13) for a 1 s integration time. Main noise contributions limiting the short-term and medium-term frequency stability are reviewed and estimated.
We report an experimental study of an all-optical three-photon-absorption resonance (known as an "N-resonance") and discuss its potential application as an alternative to atomic clocks based on coherent population trapping (CPT). We present measurements of the N-resonance contrast, width and light shift for /sup 87/Rb under various conditions including both D/sub 1/ and D/sub 2/ optical transitions. Under conditions such that first-order light shifts cancel, we observe promising short-term frequency stability (/spl sim/ 1.5 /spl times/ 10/sup -11/ /spl tau//sub - 1/2 /) for an N-resonance on the Di transition of /sup 87/ Rb vapor.