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Physical Review A

Hyperfine interaction in the Autler-Townes effect: Control of two-photon selection rules in the Morris-Shore basis

A. Cinins, Dmitry K. Efimov, Martins Bruvelis, K. Miculis, Teodora Kirova, Nikolai N. Bezuglov, I. I. Ryabtsev, Marcis P. Auzinsh, Aigars Ekers

Published Jun 18, 2024• 4 citations
Publisher

Abstract

Earlier research highlighted the absence of certain bright peaks in Autler-Townes laser excitation spectra of alkali-metal atoms and attributed this phenomenon to a specific architecture of adiabatic (or ``laser-dressed'') states in hyperfine (HF) components. Here we have studied the dressed states' properties in several two-photon excitation schemes where constructive and destructive interferences between HF excitation pathways limit the available two-photon transitions. The analysis reveals a mechanism by which this interference reduces the conventional two-photon selection rule for the total angular momentum $F$, from $\mathrm{\ensuremath{\Delta}}F=0,\ifmmode\pm\else\textpm\fi{}1$ to $\mathrm{\ensuremath{\Delta}}F\ensuremath{\equiv}0$. Our discovery presents a practical method for selectively controlling the populations of unresolvable HF $F$ components of $n{s}_{1/2}$ Rydberg states in alkali-metal atoms. Using numerical simulations with sodium and rubidium atoms, we demonstrate that by blocking the effects of HF interaction with a specially tuned auxiliary control-laser field, the deviations from the ideal selectivity of the HF components population can be lower than $0.01%$ for Na and $0.001%$ for Rb atoms.

DOI
10.1103/physreva.109.063116

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Hyperfine interaction in the Autler-Townes effect II: control of two-photon selection rules in the Morris-Shore basis

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We investigated the absence of certain bright peaks in Autler-Townes laser excitation spectra of alkali metal atoms. Our research revealed that these dips in the spectra are caused by a specific architecture of adiabatic (or ``laser-dressed'') states in hyperfine (HF) components. The dressed states' analysis pinpointed several cases where constructive and destructive interference between HF excitation pathways in a two-photon excitation scheme limits the available two-photon transitions. This results in a reduction of the conventional two-photon selection rule for the total angular momentum $F$, from $ΔF= 0,\pm 1$ to $ΔF\equiv 0$. Our discovery presents practical methods for selectively controlling the populations of unresolvable HF $F$-components of $ns_{1/2}$ Rydberg states in alkali metal atoms. Using numerical simulations with sodium and rubidium atoms, we demonstrate that by blocking the effects of HF interaction with a specially tuned auxiliary control laser field, the deviations from the ideal selectivity of the HF components population can be lower than $0.01\%$ for Na and $0.001\%$ for Rb atoms.

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Hyperfine interaction in the Autler-Townes effect: The formation of bright, dark, and chameleon states

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This paper is devoted to clarifying the implications of hyperfine (HF) interaction in the formation of adiabatic (i.e., ``laser-dressed'') states and their expression in the Autler-Townes (AT) spectra. We first use the Morris-Shore model [J. R. Morris and B. W. Shore, Phys. Rev. A 27, 906 (1983)] to illustrate how bright and dark states are formed in a simple reference system where closely spaced energy levels are coupled to a single state with a strong laser field with the respective Rabi frequency ${\mathrm{\ensuremath{\Omega}}}_{S}$. We then expand the simulations to realistic hyperfine level systems in Na atoms for a more general case when non-negligible HF interaction can be treated as a perturbation in the total system Hamiltonian. A numerical analysis of the adiabatic states that are formed by coupling of the $3{p}_{3/2}$ and $4{d}_{5/2}$ states by the strong laser field and probed by a weak laser field on the $3{s}_{1/2}\ensuremath{-}3{p}_{3/2}$ transition yielded two important conclusions. Firstly, the perturbation introduced by the HF interaction leads to the observation of what we term ``chameleon'' states---states that change their appearance in the AT spectrum, behaving as bright states at small to moderate ${\mathrm{\ensuremath{\Omega}}}_{S}$, and fading from the spectrum similarly to dark states when ${\mathrm{\ensuremath{\Omega}}}_{S}$ is much larger than the HF splitting of the $3{p}_{3/2}$ state. Secondly, excitation by the probe field from two different HF levels of the ground state allows one to address orthogonal sets of adiabatic states; this enables, with appropriate choice of ${\mathrm{\ensuremath{\Omega}}}_{S}$ and the involved quantum states, a selective excitation of otherwise unresolved hyperfine levels in excited electronic states.

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O. S. Mishina, A. S. Sheremet, Ларионов Николай Владимирович +1 more

The Autler—Townes effect is considered for the case where a strong control field acts in the frequency profile of a hyperfine transition taking into account the hyperfine interaction. An exact expression is derived for the susceptibility of the medium with respect to a probe field that acts in the frequency profile of a coupled transition of the alkaliatom D 1 line. It is shown that the hyperfine interaction in the excited state may substantially modify the susceptibility of the medium. In particular, it is shown that, when the control field is tuned to wings of atomic transitions, the structure of the Autler—Townes resonances appears to be noticeably differing from what is predicted by the Λ-scheme approximation. It is found that tuning of the control field frequency to between hyperfine components of the excited state enhances the resonant structure in this region. The results are discussed in terms of the quantum memory protocols based on the effects of Raman scattering and electromagnetically induced transparency.

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The resonant dynamic Stark effect, observed in the Autler-Townes (AT) splitting, plays a central role in ultrafast strong-field physics. Recent experiments have demonstrated the phase control of the AT doublet in atomic resonance-enhanced multiphoton ionization using intense resonant shaped femtosecond laser pulses [Bayer et al., Adv. Chem. Phys. 159, 235 (2016)]. Based on a two-state model, we showed that the underlying control mechanism is the selective population of dressed states (SPODS). In this work, we use a numerical model to calculate the photoelectron momentum distribution (PMD) based on the ab initio solution of the two-dimensional (2D) time-dependent Schr\"odinger equation (TDSE) to obtain a more complete physical picture of the nonperturbative control of the AT doublet. The 2D-TDSE model reproduces the ultrafast switching among the AT components while also revealing deviations from the signatures predicted by the two-state model. These deviations are attributed to the influence of additional intermediate states. To rationalize our observations, we propose a refined five-state model that includes all significantly populated bound states from the full calculation and accurately reproduces the 2D PMD. Based on the validated five-state model, we conduct a dressed-state analysis which provides a clear physical picture of the SPODS mechanism in a multistate system and sheds light on the role of the intermediate states in strong-field control.

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Autler-Townes effect in the D1-line hyperfine structure of an alkali atom

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We consider the Autler-Townes effect when a strong coupling field is applied in the hyperfine manifold of an alkali atom. Explicit solution is obtained in the case of the D1-line. We show how the hyperfine interaction modifies the dressing effects associated with the strong field as well as the sample susceptibility with respect to the probe mode. Particularly, if the strong field is far detuned from the atomic resonance line the Autler-Townes structure differs significantly from the prediction of the Lambda-type approximation. We also find that tuning the strong field in between the upper state hyperfine components enhances the Autler-Townes effect. The results are discussed in the context of quantum memory protocols based on the stimulated Raman process or EIT effect.

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Direct observation of two-photon-resonance Autler-Townes splitting of atomic sodium

Wankai Li, Yixuan Wang, Xing Li +3 more

A two-photon resonance in the sodium atom $3s\text{\ensuremath{-}}4s$ transition is investigated in the strong coupling regime with photoelectron momentum imaging techniques. The kinetic energies of the ionized electron map out the eigenenergies of the dressed states and emerge as the Autler-Townes (AT) splitting, which is proportional to the laser intensity due to the two-photon nature. The partial wave analysis of the angular distribution of the photoelectrons reveals the relative phase shift from dressed states which is related to the attosecond ionization time delays. The phase shift between the two electron wave packets produced from AT splitting are attributed to the combination of the Coulomb phase and the quantum defect phase.

Physical Review A•Jun 2, 2025•6 citations
Earlier research highlighted the absence of certain bright peaks in Autler-Townes laser excitation spectra of alkali-metal atoms and attributed this phenomenon to a specific architecture of adiabatic (or ``laser-dressed'') states in hyperfine (HF) components. Here we have studied the dressed states' properties in several two-photon excitation schemes where constructive and destructive interferences between HF excitation pathways limit the available two-photon transitions. The analysis reveals a mechanism by which this interference reduces the conventional two-photon selection rule for the total angular momentum FFF, from \ensuremathΔF=0,\ifmmode±\else\textpm\fi1\mathrm{\ensuremath{\Delta}}F=0,\ifmmode\pm\else\textpm\fi{}1\ensuremathΔF=0,\ifmmode±\else\textpm\fi1 to \ensuremathΔF\ensuremath≡0\mathrm{\ensuremath{\Delta}}F\ensuremath{\equiv}0\ensuremathΔF\ensuremath≡0. Our discovery presents a practical method for selectively controlling the populations of unresolvable HF FFF components of ns1/2n{s}_{1/2}ns1/2​ Rydberg states in alkali-metal atoms. Using numerical simulations with sodium and rubidium atoms, we demonstrate that by blocking the effects of HF interaction with a specially tuned auxiliary control-laser field, the deviations from the ideal selectivity of the HF components population can be lower than 0.010.01%0.01 for Na and 0.0010.001%0.001 for Rb atoms.
We investigated the absence of certain bright peaks in Autler-Townes laser excitation spectra of alkali metal atoms. Our research revealed that these dips in the spectra are caused by a specific architecture of adiabatic (or ``laser-dressed'') states in hyperfine (HF) components. The dressed states' analysis pinpointed several cases where constructive and destructive interference between HF excitation pathways in a two-photon excitation scheme limits the available two-photon transitions. This results in a reduction of the conventional two-photon selection rule for the total angular momentum FFF, from ΔF=0,±1ΔF= 0,\pm 1ΔF=0,±1 to ΔF≡0ΔF\equiv 0ΔF≡0. Our discovery presents practical methods for selectively controlling the populations of unresolvable HF FFF-components of ns1/2ns_{1/2}ns1/2​ Rydberg states in alkali metal atoms. Using numerical simulations with sodium and rubidium atoms, we demonstrate that by blocking the effects of HF interaction with a specially tuned auxiliary control laser field, the deviations from the ideal selectivity of the HF components population can be lower than 0.01%0.01\%0.01% for Na and 0.001%0.001\%0.001% for Rb atoms.
This paper is devoted to clarifying the implications of hyperfine (HF) interaction in the formation of adiabatic (i.e., ``laser-dressed'') states and their expression in the Autler-Townes (AT) spectra. We first use the Morris-Shore model [J. R. Morris and B. W. Shore, Phys. Rev. A 27, 906 (1983)] to illustrate how bright and dark states are formed in a simple reference system where closely spaced energy levels are coupled to a single state with a strong laser field with the respective Rabi frequency ${\mathrm{\ensuremath{\Omega}}}_{S}$. We then expand the simulations to realistic hyperfine level systems in Na atoms for a more general case when non-negligible HF interaction can be treated as a perturbation in the total system Hamiltonian. A numerical analysis of the adiabatic states that are formed by coupling of the 3p3/23{p}_{3/2}3p3/2​ and 4d5/24{d}_{5/2}4d5/2​ states by the strong laser field and probed by a weak laser field on the $3{s}_{1/2}\ensuremath{-}3{p}_{3/2}$ transition yielded two important conclusions. Firstly, the perturbation introduced by the HF interaction leads to the observation of what we term ``chameleon'' states---states that change their appearance in the AT spectrum, behaving as bright states at small to moderate ${\mathrm{\ensuremath{\Omega}}}_{S}$, and fading from the spectrum similarly to dark states when ${\mathrm{\ensuremath{\Omega}}}_{S}$ is much larger than the HF splitting of the 3p3/23{p}_{3/2}3p3/2​ state. Secondly, excitation by the probe field from two different HF levels of the ground state allows one to address orthogonal sets of adiabatic states; this enables, with appropriate choice of ${\mathrm{\ensuremath{\Omega}}}_{S}$ and the involved quantum states, a selective excitation of otherwise unresolved hyperfine levels in excited electronic states.
The Autler—Townes effect is considered for the case where a strong control field acts in the frequency profile of a hyperfine transition taking into account the hyperfine interaction. An exact expression is derived for the susceptibility of the medium with respect to a probe field that acts in the frequency profile of a coupled transition of the alkaliatom D 1 line. It is shown that the hyperfine interaction in the excited state may substantially modify the susceptibility of the medium. In particular, it is shown that, when the control field is tuned to wings of atomic transitions, the structure of the Autler—Townes resonances appears to be noticeably differing from what is predicted by the Λ-scheme approximation. It is found that tuning of the control field frequency to between hyperfine components of the excited state enhances the resonant structure in this region. The results are discussed in terms of the quantum memory protocols based on the effects of Raman scattering and electromagnetically induced transparency.
The resonant dynamic Stark effect, observed in the Autler-Townes (AT) splitting, plays a central role in ultrafast strong-field physics. Recent experiments have demonstrated the phase control of the AT doublet in atomic resonance-enhanced multiphoton ionization using intense resonant shaped femtosecond laser pulses [Bayer et al., Adv. Chem. Phys. 159, 235 (2016)]. Based on a two-state model, we showed that the underlying control mechanism is the selective population of dressed states (SPODS). In this work, we use a numerical model to calculate the photoelectron momentum distribution (PMD) based on the ab initio solution of the two-dimensional (2D) time-dependent Schr\"odinger equation (TDSE) to obtain a more complete physical picture of the nonperturbative control of the AT doublet. The 2D-TDSE model reproduces the ultrafast switching among the AT components while also revealing deviations from the signatures predicted by the two-state model. These deviations are attributed to the influence of additional intermediate states. To rationalize our observations, we propose a refined five-state model that includes all significantly populated bound states from the full calculation and accurately reproduces the 2D PMD. Based on the validated five-state model, we conduct a dressed-state analysis which provides a clear physical picture of the SPODS mechanism in a multistate system and sheds light on the role of the intermediate states in strong-field control.
We consider the Autler-Townes effect when a strong coupling field is applied in the hyperfine manifold of an alkali atom. Explicit solution is obtained in the case of the D1-line. We show how the hyperfine interaction modifies the dressing effects associated with the strong field as well as the sample susceptibility with respect to the probe mode. Particularly, if the strong field is far detuned from the atomic resonance line the Autler-Townes structure differs significantly from the prediction of the Lambda-type approximation. We also find that tuning the strong field in between the upper state hyperfine components enhances the Autler-Townes effect. The results are discussed in the context of quantum memory protocols based on the stimulated Raman process or EIT effect.
A two-photon resonance in the sodium atom $3s\text{\ensuremath{-}}4s$ transition is investigated in the strong coupling regime with photoelectron momentum imaging techniques. The kinetic energies of the ionized electron map out the eigenenergies of the dressed states and emerge as the Autler-Townes (AT) splitting, which is proportional to the laser intensity due to the two-photon nature. The partial wave analysis of the angular distribution of the photoelectrons reveals the relative phase shift from dressed states which is related to the attosecond ionization time delays. The phase shift between the two electron wave packets produced from AT splitting are attributed to the combination of the Coulomb phase and the quantum defect phase.