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Journal of Physics Conference Series

Stray magnetic field influence on the CPT resonance in a coated Rb vacuum cell

Elena T. Taskova, Emilia A. Alipieva, G. Todorov

Published Mar 1, 2016• 3 citations
Publisher

Abstract

Interaction of a resonant laser beam with an atomic absorption medium creates population redistribution and interference between atomic levels. This anisotropy of the medium is experimentally observed as coherent population trapping (CPT) or electromagnetically induced transparency (EIT). Due to the small sub-natural width of the CPT and EIT resonances, they find wide applications in metrology, quantum optics, atom cooling. A non-compensated stray magnetic field (SMF) can change the shape and sign of the resonance or destroy it completely. In this work, we present an experimental and theoretical investigation of the influence of a stray magnetic field on the CPT resonances obtained on Zeeman sublevels of the D 1 line of 87 Rb in a paraffin-coated vacuum cell. The role is clarified of the polarization moments with different rank in creating the integral registered fluorescent signal in the presence of a stray magnetic field. It is shown that a transverse magnetic field plays an important role in changing the shape of the signal.

DOI
10.1088/1742-6596/700/1/012015

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Peculiarities of the coherent population trapping resonance in the fluorescence obtained in a coated 87 Rb cell in the presence of transverse magnetic field: theory and experiment

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Abstract We present an experimental and theoretical investigation of the influence of the transverse magnetic field (TMF) on the coherent population trapping resonances obtained on the Zeeman sublevels of the D 1 line of 87 Rb in a paraffin-coated vacuum cell. It is shown that a TMF changes the shape and sign of the resonance or destroys it completely. The role of the different rank polarization moments in the integral registered fluorescent signal in the presence of stray magnetic fields is clarified using numerical simulations.

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Magneto-optical resonance of the polarized fluorescence in a paraffin-coated87Rb vacuum cell

Elena T. Taskova, Emilia A. Alipieva, G. Todorov

In this work we investigate the magneto-optical resonance on 87Rb D1 line. In two-level degenerated system this resonance is due to the interference between the Zeeman sub-levels, created by interaction of resonance linear polarized laser beam with the atoms. The observed signal is detected by sweeping magnetic field B around its zero value. This phenomenon is also known as a Coherent Population Trapping (CPT) in Hanle-configuration. In a coated vacuum cell the fluorescence signal has a complex form, because the anti-relaxation coating preserves the created coherence, having different relaxation rates. The ground state coherence is transmitted by the laser field to the upper level; thereby polarization moments with different rank contribute to the fluorescence. The manifestation of the different polarization moments in the observed signal depends on the geometry of the experiment – direction of observation, plane of the laser polarization, polarization of the registered light. The resonances obtained in the fluorescence having different polarization are compared in order to clear up what are the contributions to the fluorescent signal from the polarization moments with different rank. The experiment is performed on the D1 87Rb line, F=2→ F=1 transition in a paraffin-coated cell. The magneto-optical resonances, detected in two orthogonal polarizations are measured. Numerical calculations with parameters, close to the experimental ones are performed by using a program, which is based on the irreducible tensor operator formalism. The results of the modelling are compared with the measured ones at different experimental conditions.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jan 8, 2015•0 citations

Nonlinear Magnetooptical Resonance in 87Rb Vapor: The Influence of Stray Magnetic Fields and Excitation Radiation Intensity on the Basic Characteristics of the Effect in Cells with Antirelaxation Coating

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The nonlinear Hanle effect is generally considered in the modern literature as a particular case of coherent population trapping (CPT) at degenerate Zeeman sublevels of the ground atomic state. The shape, amplitude, and sign of observed resonances and their dependence on the excitation parameters and observation geometry were investigated theoretically and experimentally in many studies because of the wide range of application of this effect. The sensitivity of Hanle resonances to the experimental conditions increases significantly in cells with antirelaxation coating, because the atomic ensemble retains its coherence after a large number of collisions with the cell walls. In this paper, the main attention is paid to the joint influence of the excitation radiation intensity and spurious magnetic fields on CPT resonances observed in fluorescence. The theoretical description is based on the numerical solution of an algebraic system of equations for density matrix $$\hat {\rho }$$ in the formalism of irreducible tensor operators. The parameters relating different polarization moments in each equation are visualized using the modified sparse matrix of the system. It is established by numerical simulation that the shape, width, amplitude, and sign of nonlinear magnetooptical resonances change nonmonotonically with a change in the parameters of the excitation radiation and atomic system. The presented theoretical results are in good agreement with the experimental data obtained under various conditions.

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CPT effect and its applications for weak electromagnetic field detection

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Summary form only given. We have performed experimental investigations of the coherent population trapping (CPT) phenomenon at a single hyperfine transition at the D/sub 1/ and D/sub 2/ lines of Rb in a cell, inserted inside a magnetic shield. For observation of CPT dark resonances at a single hyperfine transition the Zeeman degeneracy has to be removed. This was achieved by applying a homogeneous magnetic field H/sub 1/, parallel to the laser beam and scanned in both directions around zero value. Additional coil produced constant magnetic or RF electromagnetic field H/sub 2/ perpendicular to the beam propagation. The fluorescence signal was registered in order to investigate the influence of the additional electromagnetic field on the dark line parameters. It was observed that the width and the contrast of the dark line are very sensitive to the applied field H/sub 2./ Increasing the value/amplitude of H/sub 2/ causes increase of the width and decrease of the contrast of the CPT resonances.

Trans Black Sea Region Symposium on Applied Electromagnetism•Nov 11, 2002•0 citations

Coherent population trapping resonance structure in paraffin-coated Rb vacuum cells

S. Gateva, Emilia A. Alipieva, Elena T. Taskova +1 more

The fast development of CPT applications and the need of good magnetooptical sensors result in an increased interest in the Coherent Population Trapping (CPT) resonances and the processes that determine their shape. In this work the shape and width of the CPT resonances are investigated in two different paraffin-coated Rb vapor cells from point of view of understanding the processes influencing the shape of the resonances and building of miniature and sensitive detector. The dependence of the shape of the resonances on the laser power is measured. Narrow resonances on three hyperfine transitions of the D1 87Rb line are registered. For explanation of the bright structure in the resonance shapes at low laser powers analysis of the influence of different processes is made.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Oct 8, 2010•4 citations

Manifestation of high-rank polarization moments in the fluorescence CPT resonance

Emilia A. Alipieva, Elena T. Taskova, S. Gateva +1 more

Coherent Population Trapping (CPT) resonance obtained with linearly polarized laser beam through magnetic field sweep (Hanle configuration) was investigated in 87Rb D1 line. Influence of the coherence due to high-rank polarization moment (hexadecapole moment), created in the medium, on the CPT resonance shape was calculated and experimentally detected in fluorescence. It was observed as an inverted structure at a high power of excitation. To distinguish resonances due to coherence between Zeeman sub-levels with ΔmF=2 from that with ΔmF=4, the Larmour frequency ωLmodulated by applying an a.c. magnetic field (a.c. MF). Resonance signal at frequency corresponding to 4ωL observed in a fluorescence, and after lock-in on the frequency corresponding to frequency difference between sub-levels ΔmF=4.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Dec 22, 2008•0 citations
Interaction of a resonant laser beam with an atomic absorption medium creates population redistribution and interference between atomic levels. This anisotropy of the medium is experimentally observed as coherent population trapping (CPT) or electromagnetically induced transparency (EIT). Due to the small sub-natural width of the CPT and EIT resonances, they find wide applications in metrology, quantum optics, atom cooling. A non-compensated stray magnetic field (SMF) can change the shape and sign of the resonance or destroy it completely. In this work, we present an experimental and theoretical investigation of the influence of a stray magnetic field on the CPT resonances obtained on Zeeman sublevels of the D 1 line of 87 Rb in a paraffin-coated vacuum cell. The role is clarified of the polarization moments with different rank in creating the integral registered fluorescent signal in the presence of a stray magnetic field. It is shown that a transverse magnetic field plays an important role in changing the shape of the signal.
Abstract We present an experimental and theoretical investigation of the influence of the transverse magnetic field (TMF) on the coherent population trapping resonances obtained on the Zeeman sublevels of the D 1 line of 87 Rb in a paraffin-coated vacuum cell. It is shown that a TMF changes the shape and sign of the resonance or destroys it completely. The role of the different rank polarization moments in the integral registered fluorescent signal in the presence of stray magnetic fields is clarified using numerical simulations.
In this work we investigate the magneto-optical resonance on 87Rb D1 line. In two-level degenerated system this resonance is due to the interference between the Zeeman sub-levels, created by interaction of resonance linear polarized laser beam with the atoms. The observed signal is detected by sweeping magnetic field B around its zero value. This phenomenon is also known as a Coherent Population Trapping (CPT) in Hanle-configuration. In a coated vacuum cell the fluorescence signal has a complex form, because the anti-relaxation coating preserves the created coherence, having different relaxation rates. The ground state coherence is transmitted by the laser field to the upper level; thereby polarization moments with different rank contribute to the fluorescence. The manifestation of the different polarization moments in the observed signal depends on the geometry of the experiment – direction of observation, plane of the laser polarization, polarization of the registered light. The resonances obtained in the fluorescence having different polarization are compared in order to clear up what are the contributions to the fluorescent signal from the polarization moments with different rank. The experiment is performed on the D1 87Rb line, F=2→ F=1 transition in a paraffin-coated cell. The magneto-optical resonances, detected in two orthogonal polarizations are measured. Numerical calculations with parameters, close to the experimental ones are performed by using a program, which is based on the irreducible tensor operator formalism. The results of the modelling are compared with the measured ones at different experimental conditions.
The nonlinear Hanle effect is generally considered in the modern literature as a particular case of coherent population trapping (CPT) at degenerate Zeeman sublevels of the ground atomic state. The shape, amplitude, and sign of observed resonances and their dependence on the excitation parameters and observation geometry were investigated theoretically and experimentally in many studies because of the wide range of application of this effect. The sensitivity of Hanle resonances to the experimental conditions increases significantly in cells with antirelaxation coating, because the atomic ensemble retains its coherence after a large number of collisions with the cell walls. In this paper, the main attention is paid to the joint influence of the excitation radiation intensity and spurious magnetic fields on CPT resonances observed in fluorescence. The theoretical description is based on the numerical solution of an algebraic system of equations for density matrix ρ^\hat {\rho }ρ^​ in the formalism of irreducible tensor operators. The parameters relating different polarization moments in each equation are visualized using the modified sparse matrix of the system. It is established by numerical simulation that the shape, width, amplitude, and sign of nonlinear magnetooptical resonances change nonmonotonically with a change in the parameters of the excitation radiation and atomic system. The presented theoretical results are in good agreement with the experimental data obtained under various conditions.
Summary form only given. We have performed experimental investigations of the coherent population trapping (CPT) phenomenon at a single hyperfine transition at the D/sub 1/ and D/sub 2/ lines of Rb in a cell, inserted inside a magnetic shield. For observation of CPT dark resonances at a single hyperfine transition the Zeeman degeneracy has to be removed. This was achieved by applying a homogeneous magnetic field H/sub 1/, parallel to the laser beam and scanned in both directions around zero value. Additional coil produced constant magnetic or RF electromagnetic field H/sub 2/ perpendicular to the beam propagation. The fluorescence signal was registered in order to investigate the influence of the additional electromagnetic field on the dark line parameters. It was observed that the width and the contrast of the dark line are very sensitive to the applied field H/sub 2./ Increasing the value/amplitude of H/sub 2/ causes increase of the width and decrease of the contrast of the CPT resonances.
The fast development of CPT applications and the need of good magnetooptical sensors result in an increased interest in the Coherent Population Trapping (CPT) resonances and the processes that determine their shape. In this work the shape and width of the CPT resonances are investigated in two different paraffin-coated Rb vapor cells from point of view of understanding the processes influencing the shape of the resonances and building of miniature and sensitive detector. The dependence of the shape of the resonances on the laser power is measured. Narrow resonances on three hyperfine transitions of the D1 87Rb line are registered. For explanation of the bright structure in the resonance shapes at low laser powers analysis of the influence of different processes is made.
Coherent Population Trapping (CPT) resonance obtained with linearly polarized laser beam through magnetic field sweep (Hanle configuration) was investigated in 87Rb D1 line. Influence of the coherence due to high-rank polarization moment (hexadecapole moment), created in the medium, on the CPT resonance shape was calculated and experimentally detected in fluorescence. It was observed as an inverted structure at a high power of excitation. To distinguish resonances due to coherence between Zeeman sub-levels with ΔmF=2 from that with ΔmF=4, the Larmour frequency ωLmodulated by applying an a.c. magnetic field (a.c. MF). Resonance signal at frequency corresponding to 4ωL observed in a fluorescence, and after lock-in on the frequency corresponding to frequency difference between sub-levels ΔmF=4.