Coherent Population Trapping resonances on lower atomic levels of Doppler broadened optical lines (original) (raw)
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Coherent population trapping resonances at lower atomic levels of Doppler broadened optical lines
Quantum Electronics, 2014
We have detected and analysed narrow high-contrast coherent population trapping (CPT) resonances, which are induced in absorption of the weak probe light beam by the counterpropagating two-frequency pumping radiation. Our experimental investigations have been carried out on an example of nonclosed three level Λ-systems formed by spectral components of the Doppler broadened D 2 line of cesium atoms. We have established that CPT resonances in transmission of the probe beam (in the cesium vapor), at definite conditions, may have not only more contrast but also much lesser width in comparison with well-known CPT resonances in transmission of the corresponding two-frequency pumping radiation. Thus CPT resonances, detected by the elaborated method, may be used in atomic frequency standards and sensitive magnetometers (based on the CPT phenomenon) and also in ultahigh resolution spectroscopy of atoms and molecules.
Light shift of coherent population trapping resonances
Proceedings of SPIE, 1999
Although the frequency position of the non-coupled state in coherent population trapping does not depend on light intensities this is not true for the experimentally observed dark resonance minimum. For precision applications this shift constitutes a major systematic effect. We have measured the light shift in an atomic cesium vapor as a function of buffer gas pressure. The experimental data for the unbuffered vapor can be reproduced quantitatively with a simple model taking into account the atomic velocity distribution and the excited state hyperfine structure. The buffered vapor requires a more complicated model.
Physical Review A, 2005
The investigation of the coherent-population-trapping ͑CPT͒ resonance on the degenerate two-level system of the ͑F g =2→ F e =1͒ transition of the 87 Rb D 1 line by means of a Hanle effect configuration in an uncoated vacuum cell ͓Opt. Lett. 28, 1817 ͑2003͔͒ has shown that the measured in fluorescence resonance has a complex shape-a very narrow ͑about 1 mG͒ structure superimposed on a broader one ͑about few tens of mG͒. In this work, the dependence of the width and amplitude of the CPT resonance structures are measured at different laser power densities when the registration is in fluorescence and transmission. While the narrow resonance width does not change within the limits of the accuracy of our measurements, the wide resonance width dependence is complex and is different in fluorescence and transmission. The origins of the observed resonance width narrowing of the CPT resonance structures registered in fluorescence and transmission are discussed.
Characterization of coherent population-trapping resonances as atomic frequency references
Journal of The Optical Society of America B-optical Physics, 2001
A low-cost, potentially compact and robust microwave frequency reference can be constructed by use of vertical-cavity surface-emitting lasers and coherent population-trapping resonances in Cs vapor cells. Fractional frequency instabilities of 2 ϫ 10 Ϫ11 /ͱ/s have been achieved with a minimum of 7 ϫ 10 Ϫ13 at ϭ 1000 s. The performance of this device as a function of external parameters such as light intensity, optical detuning, and cell temperature is discussed. The dependence of the dark-line resonance signal on these parameters can be understood largely by means of a simple, three-level model. The short-term stability depends critically on the optical detuning, whereas the long-term stability is limited currently by line shifts due to drifts in cell temperature.
Quantum Electronics, 2009
The conditions necessary to implement a single-photon pulse source using quantum filtering based on the coherent population trapping phenomenon in N -systems of atomic levels are determined. The dependences of dark resonance characteristics on laser field intensities are experimentally measured in Rb vapor. These dependences define optimum intensity ratios and pulse durations of used laser beams, at which the system can efficiently operate as a single-photon quantum filter. (CPT) [1, 2] is a subject of basic research and applied developments in the field of precision spectroscopy [2], metrology [3], magnetometry , and light pulse storage and conversion using coherent excitations in an atomic medium . In [8], generalized dark states (GDSs) of CPT in the (atom + field) system were considered; it was shown that GDSs can arise in both classical (coherent light states) and quantized (n-photon or Fock light states) fields. Of most interest is the consideration of GDSs in atomic level systems forming the so-called N -chains during interactions with light fields . The N -chain is a sequence of L Λ systems complemented by one resonance transition. Due to this additional transition playing the role of a dark state decay channel, CPT does not occur in such a system in the classical field. Nevertheless, the theoretical consideration shows that GDSs can be formed in such systems as well.
Femtosecond laser pulse train effect on Doppler profile of cesium resonance lines
The European Physical Journal D, 2007
We present direct observation of the velocity-selective optical pumping of the Cs ground state hyperfine levels induced by the femtosecond (fs) laser oscillator centered at either D2 (6 2 S 1/2 → 6 2 P 3/2 , 852 nm) or D1 (6 2 S 1/2 → 6 2 P 1/2 , 894 nm) cesium line. We utilized previously developed modified direct frequency comb spectroscopy (DFCS) which uses a fixed frequency comb for the excitation and a weak cw scanning probe laser centered at the 133 Cs 6 2 S 1/2 → 6 2 P 3/2 transition (D2 line) for ground levels population monitoring. The frequency comb excitation changes the usual Doppler absorption profile into a specific periodic, comblike structure. The mechanism of the velocity selective population transfer between the Cs ground state hyperfine levels induced by fs pulse train excitation is verified in a theoretical treatment of the multilevel atomic system subjected to a pulse train resonant field interaction.
Saturated-absorption spectroscopy: eliminating crossover resonances by use of copropagating beams
Optics Letters, 2003
Saturated absorption (SA) spectroscopy is widely used in the realization of frequency references for atomic transitions . In this technique, the laser beam is split into a weak probe field and a strong pump field, which are sent to the interaction cell as counterpropagating overlapping beams. Because of opposite Doppler shifts, only the atoms moving perpendicular to the radiation propagation direction resonantly interact with both laser beams. For these atoms, the pump beam saturates the transition, and the absorption spectrum of the probe shows a Doppler-free dip, the so-called velocity selective optical pumping/saturation (VSOP) resonance located at the line center. With properly chosen pump and probe beam intensities, careful adjustment of the geometry, and the elimination of stray magnetic fields, the line width of the resonance (to which we refer to as "VSOP resonance") may be as narrow as the natural width of the transition.
Absorption spectra for strong pump and probe in atomic beam of cesium atoms (2009)
2009
We calculate the pump and probe absorption spectra for the cycling F g =4→ F e = 5 transition D 2 line of 133 Cs in an atomic beam, interacting with a strong resonant + -polarized pump and a probe of comparable intensity and either − or polarization. The aim is to reproduce and analyze the experiments of Dahl et al. ͓Opt. Lett. 33, 983 ͑2008͔͒ who showed for a + -polarized pump and − -polarized probe that the pump absorption spectrum switches from an "absorption within transparency" ͑AWT͒ structure, when the probe is weaker than the pump, to a "transparency within transparency" ͑TWT͒ structure, when the probe is stronger than the pump. For all other polarization combinations, the pump spectrum displays AWT behavior at all probe intensities. We analyze our results by considering the contributions that derive from the individual m g → m e transitions. When the + -polarized pump is stronger than the − -polarized probe, the population is swept toward the m g → m e = m g + 1 transitions with the highest values of m g , and the pump absorption spectrum has an AWT structure and resembles that of an N system. However, when the probe is stronger than the pump, the population is swept toward the m g =−F g → m e = m g − 1 transition when the probe is near resonance, and to the m g = F g → m e = m g + 1 transition when the probe is detuned from resonance. The pump and probe spectra are mirror images of each other and resemble those of a V system where the probe has a peak at line center and the pump spectrum has a TWT structure. For a strong + pump and an even stronger probe, the population concentrates in the intermediate transitions, and the AWT to TWT changeover does not occur. We also show that the narrow features in the spectra at line center derive from transfer of coherence from the excited to the ground hyperfine levels.
Absorption spectra for strong pump and probe in atomic beam of cesium atoms
Physical Review A, 2009
We calculate the pump and probe absorption spectra for the cycling F g =4→ F e = 5 transition D 2 line of 133 Cs in an atomic beam, interacting with a strong resonant +-polarized pump and a probe of comparable intensity and either − or polarization. The aim is to reproduce and analyze the experiments of Dahl et al. ͓Opt. Lett. 33, 983 ͑2008͔͒ who showed for a +-polarized pump and −-polarized probe that the pump absorption spectrum switches from an "absorption within transparency" ͑AWT͒ structure, when the probe is weaker than the pump, to a "transparency within transparency" ͑TWT͒ structure, when the probe is stronger than the pump. For all other polarization combinations, the pump spectrum displays AWT behavior at all probe intensities. We analyze our results by considering the contributions that derive from the individual m g → m e transitions. When the +-polarized pump is stronger than the −-polarized probe, the population is swept toward the m g → m e = m g + 1 transitions with the highest values of m g , and the pump absorption spectrum has an AWT structure and resembles that of an N system. However, when the probe is stronger than the pump, the population is swept toward the m g =−F g → m e = m g − 1 transition when the probe is near resonance, and to the m g = F g → m e = m g + 1 transition when the probe is detuned from resonance. The pump and probe spectra are mirror images of each other and resemble those of a V system where the probe has a peak at line center and the pump spectrum has a TWT structure. For a strong + pump and an even stronger probe, the population concentrates in the intermediate transitions, and the AWT to TWT changeover does not occur. We also show that the narrow features in the spectra at line center derive from transfer of coherence from the excited to the ground hyperfine levels.