We have theoretically and experimentally studied the spectroscopic properties of dressed levels in a strong monochromatic field, and propose a model of cascade splitting of two atomic energy levels. In this model two related dressed levels can be split into four levels, and transitions connecting four new levels will constitute spectroscopic structures. Two types of proof-in-principle experiments are performed to verify the model. One experiment measures the probe absorption spectra of a degenerate two-level atomic system with two strong monochromatic coupling fields. The system consists of ${5}^{2}{S}_{1/2},F=2$ and ${5}^{2}{P}_{3/2},{F}^{\ensuremath{'}}=3$ states of $^{87}\mathrm{Rb}$ atoms in a magneto-optical trap (MOT) as well as the cooling beams and an additional coupling field. New spectral features are observed and proven to be due to the transitions of new levels generated by splitting of the dressed levels. The other experiment measures the pump-probe spectra in a degenerate two-level atomic system with one strong monochromatic coupling field. The system consists of ${5}^{2}{S}_{1/2},F=2$ and ${5}^{2}{P}_{3/2},{F}^{\ensuremath{'}}=3$ states of the $^{87}\mathrm{Rb}$ atom in a magneto-optical trap and one coupling field. We have observed spectral features that obviously differ from the prediction that comes from the two-level dressed-atom approach. They cannot be explained by existing theories. The model of cascade splitting of two atomic energy levels is employed to explain the observations in these two types of experiments.We have theoretically and experimentally studied the spectroscopic properties of dressed levels in a strong monochromatic field, and propose a model of cascade splitting of two atomic energy levels. In this model two related dressed levels can be split into four levels, and transitions connecting four new levels will constitute spectroscopic structures. Two types of proof-in-principle experiments are performed to verify the model. One experiment measures the probe absorption spectra of a degenerate two-level atomic system with two strong monochromatic coupling fields. The system consists of ${5}^{2}{S}_{1/2},F=2$ and ${5}^{2}{P}_{3/2},{F}^{\ensuremath{'}}=3$ states of $^{87}\mathrm{Rb}$ atoms in a magneto-optical trap (MOT) as well as the cooling beams and an additional coupling field. New spectral features are observed and proven to be due to the transitions of new levels generated by splitting of the dressed levels. The other experiment measures the pump-probe spectra in a degenerate two-level atomic system with one strong monochromatic coupling field. The system consists of ${5}^{2}{S}_{1/2},F=2$ and ${5}^{2}{P}_{3/2},{F}^{\ensuremath{'}}=3$ states of the $^{87}\mathrm{Rb}$ atom in a magneto-optical trap and one coupling field. We have observed spectral features that obviously differ from the prediction that comes from the two-level dressed-atom approach. They cannot be explained by existing theories. The model of cascade splitting of two atomic energy levels is employed to explain the observations in these two types of experiments.

Physical Review ASep 5, 20143 citations

Amplitude-modulated optical double resonance

van K.A.H. Leeuwen, Michael Francis

We have investigated the interaction between bichromatic optical fields and atomic transitions. We have considered both the interaction of a saturating bichromatic field in the form of a 100% amplitude-modulated field resonantly interacting with a single atomic transition as well as the interaction of a pair of 100% amplitude-modulated fields with two coupled atomic transitions. In our studies of a single atomic transition resonantly excited by a 100% amplitude-modulated field we have used a fully quantum-electrodynamical analysis to model the Autler-Townes effect induced by a bichromatic optical field. We find that the effect induced by a bichromatic field is markedly different from the effect produced by a monochromatic exciting field. We have derived analytic expressions for the bichromatic Autler-Townes absorption spectrum. The absorption spectrum consists of equally spaced lines spaced by the modulation frequency. The linewidths of neighboring lines alternate as functions of the field strength. Experimentally, we observed this spectrum for both resonant and detuned 100% amplitude-modulated driving fields by monitoring the absorption of a weak monochromatic field as it was tuned about the resonance frequency of the 3²P₃/₂(F = 3, mF = 3) ↔ 4²D₅/₂(F = 4, mF = 4) transition while driving the 3²S₁/₂(F = 2, mF = 2) ↔ 3²P₃/₂(F = 3, mF = 3) transition with a saturating 100% amplitude-modulated field. We found excellent agreement between our predicted and measured spectra. We then investigated the resonant interaction between a pair of 100% amplitude-modulated fields and two atomic transitions sharing a common atomic level. We considered both a three-level atomic cascade system and a three-level atomic lambda system. We examined the effect that the relative phase between the two modulations has on the rate at which the modulated fields are absorbed. We find that the saturated time-averaged field absorption exhibits parametric resonances in both the cascade and lambda systems. The time-averaged absorption is strongly dependent upon the relative phase of modulation between the two fields and for certain phase differences the time-averaged absorption can be enhanced over the maximum saturated absorption experienced by cw fields of the same time-averaged intensities. We also find that the stationary atomic response exhibits periodic oscillations and for the cascade system periodic two-photon inversions of up to 40% can be achieved. We further find dark absorption resonances as a function of phase in the lambda system. We analyze the results from the point of view of semi-classical adiabatic dressed states.We have investigated the interaction between bichromatic optical fields and atomic transitions. We have considered both the interaction of a saturating bichromatic field in the form of a 100% amplitude-modulated field resonantly interacting with a single atomic transition as well as the interaction of a pair of 100% amplitude-modulated fields with two coupled atomic transitions. In our studies of a single atomic transition resonantly excited by a 100% amplitude-modulated field we have used a fully quantum-electrodynamical analysis to model the Autler-Townes effect induced by a bichromatic optical field. We find that the effect induced by a bichromatic field is markedly different from the effect produced by a monochromatic exciting field. We have derived analytic expressions for the bichromatic Autler-Townes absorption spectrum. The absorption spectrum consists of equally spaced lines spaced by the modulation frequency. The linewidths of neighboring lines alternate as functions of the field strength. Experimentally, we observed this spectrum for both resonant and detuned 100% amplitude-modulated driving fields by monitoring the absorption of a weak monochromatic field as it was tuned about the resonance frequency of the 3²P₃/₂(F = 3, mF = 3) ↔ 4²D₅/₂(F = 4, mF = 4) transition while driving the 3²S₁/₂(F = 2, mF = 2) ↔ 3²P₃/₂(F = 3, mF = 3) transition with a saturating 100% amplitude-modulated field. We found excellent agreement between our predicted and measured spectra. We then investigated the resonant interaction between a pair of 100% amplitude-modulated fields and two atomic transitions sharing a common atomic level. We considered both a three-level atomic cascade system and a three-level atomic lambda system. We examined the effect that the relative phase between the two modulations has on the rate at which the modulated fields are absorbed. We find that the saturated time-averaged field absorption exhibits parametric resonances in both the cascade and lambda systems. The time-averaged absorption is strongly dependent upon the relative phase of modulation between the two fields and for certain phase differences the time-averaged absorption can be enhanced over the maximum saturated absorption experienced by cw fields of the same time-averaged intensities. We also find that the stationary atomic response exhibits periodic oscillations and for the cascade system periodic two-photon inversions of up to 40% can be achieved. We further find dark absorption resonances as a function of phase in the lambda system. We analyze the results from the point of view of semi-classical adiabatic dressed states.

Jan 1, 19980 citations

Frequency-Correlation Effects in Cascade Transitions Involving Stimulated Emission

Helen K. Holt

Physical Review LettersNov 27, 196736 citations

Linear susceptibility of a three-level system driven by an intense multimode laser field

V. Yu. Finkel'Shteǐn

A theory of ac Stark splitting at double resonance in a three-level system is presented, the upper and lower transitions being coupled to a near-resonant intense multimode field and a weak monochromatic field, respectively. Linear response to a weak field is considered. The analytical treatment calling into action a diagram technique and the quasistationary-states method is carried out beyond the limits of perturbation theory and the nonresonant approximation. The multimode structure of the radiation spectrum results in a quasi-periodicity of the field-correlation function. It leads to a strong modulation of the absorbtion line shape with a period $\frac{1}{2}\ensuremath{\Delta}{\ensuremath{\nu}}_{0}$ where $\ensuremath{\Delta}{\ensuremath{\nu}}_{0}$ is the intermode interval. The role of different weakening effects such as spontaneous decay of the levels, the finite pulse duration, and instrumental and natural fluctuations of a single mode is studied. The last effect is shown to be the most important, and a possible method of direct measurement of the natural-fluctuations' correlation function is proposed.A theory of ac Stark splitting at double resonance in a three-level system is presented, the upper and lower transitions being coupled to a near-resonant intense multimode field and a weak monochromatic field, respectively. Linear response to a weak field is considered. The analytical treatment calling into action a diagram technique and the quasistationary-states method is carried out beyond the limits of perturbation theory and the nonresonant approximation. The multimode structure of the radiation spectrum results in a quasi-periodicity of the field-correlation function. It leads to a strong modulation of the absorbtion line shape with a period $\frac{1}{2}\ensuremath{\Delta}{\ensuremath{\nu}}_{0}$ where $\ensuremath{\Delta}{\ensuremath{\nu}}_{0}$ is the intermode interval. The role of different weakening effects such as spontaneous decay of the levels, the finite pulse duration, and instrumental and natural fluctuations of a single mode is studied. The last effect is shown to be the most important, and a possible method of direct measurement of the natural-fluctuations' correlation function is proposed.

Physical Review AFeb 1, 19834 citations

Frequency-Correlation Effects in Cascade Transitions Involving Stimulated Emission

Helen K. Holt

Physical Review LettersJul 15, 19683 citations

{5}^{2}{S}_{1/2},F=2

and ${5}^{2}{P}_{3/2},{F}^{\ensuremath{'}}=3$ states of

^{87}\mathrm{Rb}

atoms in a magneto-optical trap (MOT) as well as the cooling beams and an additional coupling field. New spectral features are observed and proven to be due to the transitions of new levels generated by splitting of the dressed levels. The other experiment measures the pump-probe spectra in a degenerate two-level atomic system with one strong monochromatic coupling field. The system consists of

{5}^{2}{S}_{1/2},F=2

and ${5}^{2}{P}_{3/2},{F}^{\ensuremath{'}}=3$ states of the

^{87}\mathrm{Rb}

atom in a magneto-optical trap and one coupling field. We have observed spectral features that obviously differ from the prediction that comes from the two-level dressed-atom approach. They cannot be explained by existing theories. The model of cascade splitting of two atomic energy levels is employed to explain the observations in these two types of experiments.