Physical Review Letters

Observation of Amplification in a Strongly Driven Two-Level Atomic System at Optical Frequencies

F. Y. Wu, Shaoul Ezekiel, M. Ducloy, B. R. Mollow

Published May 9, 1977• 488 citations

Abstract

We report the observation of optical amplification in a two-level atomic system driven by a strong, resonant field. By exciting an atomic beam of two-level sodium atoms simultaneously with a strong, fixed-frequency driving field and a weak, tunable, probe field, we have measured the absorption (amplification) line-shape function for several values of driving field strength. In addition, we have verified theoretical predictions that higher amplification is obtained when the strong field is detuned from exact resonance.

DOI: 10.1103/physrevlett.38.1077

Related papers

Spontaneous emission and absorption properties of a driven three-level system

Lorenzo M. Narducci, Marlan O. Scully, Gian‐Luca Oppo +2 more

We investigate the steady-state spontaneous emission spectrum of a three-level atom driven by two coherent fields and the absorption spectrum of a weak probe passing through a collection of such driven atoms. We find that the fluorescence spectrum is strongly affected by the decay rates of all the levels involved in the atomic evolution and not just by the decay parameters of the specific transition whose emission spectrum is being monitored. In particular, the spectral components can acquire very different widths and peak heights relative to the case of the standard resonance fluorescence in which a two-level system is driven by a single near-resonant field. An external probe signal passing through the gas of three-level atoms may be absorbed or amplified, as in the standard two-level case, but under specific operating conditions, amplification (or absorption) occurs over the entire range where the atomic response is appreciable. In this case the existence of amplification or absorption is controlled solely by the population difference between two dressed states of the system. We provide numerical results in support of our arguments for arbitrary values of the atomic and field parameters and also develop an analytic description in the limit of strong driving fields that leads to explicit line-shape and linewidth formulas.

Physical Review AAug 1, 1990284 citations

Absorption spectrum of a strongly driven atom

S Yeh

The absorption spectrum of a weak probe radiation by a two-level atom strongly driven by an intense radiation field is examined. Using a Green's function method developed for calculations of general multiphoton processes, the author obtains some earlier results in which the spectrum has regions (in the probe frequency domain) of amplification and regions of attenuation. Such a spectrum is shown explicitly to be due to a coherent interference effect arising from the interaction of the atom with the vacuum field. Furthermore, an equation that relates the area under the amplification part of the spectrum to that under the attenuation part is obtained. This indicates that amplification cannot occur if a very-wide-band probe beam is used instead of a narrow-band one. At high driving intensities the absorption spectrum is shown explicitly to be inversely proportional to the Rabi frequency and has a dispersion-like behaviour near the Rabi sidebands at driving resonance.

Journal of Physics B Atomic and Molecular PhysicsSep 28, 19826 citations

Observation of subharmonic resonances of the Rabi frequency in the absorption spectrum of a two-level atom in a bichromatic field

Stephanos Papademetriou, Stephen H. Chakmakjian, Carlos R. Stroud

The interaction of a strong bichromatic field with a two-level atom has been the subject of numerous experimental and theoretical investigations. We performed an experimental study of the Interaction of an intense 100% amplitude-modulated (AM) field with an ensemble of homogeneously broadened two-level atoms. An optically pumped sodium atomic beam is used as the atomic medium. The field is created by interfering two intense frequency-stabilized laser fields. The frequency of one field is held fixed while another field of equal amplitude is scanned in frequency. The beat frequency produced by interfering the two laser fields is equal to twice the modulation frequency of a 100% AM field. We monitor the time-averaged fluorescent intensity of the atoms as the frequency separation between the two fields is varied. A similar experiment was done in the past in the rf regime.1 For the first time, we report the observation of multiple, well-resolved resonances in the absorption spectrum of the field in the optical regime. We present data and theory for several values of detuning between the fixed field and atomic resonance. The experimental results are in good agreement with theory.

Annual Meeting Optical Society of AmericaJan 1, 19900 citations

Induced gain and modified absorption of a weak probe beam in a strongly driven sodium vapor

Mark T. Gruneisen, Kenneth R. MacDonald, Robert W. Boyd

We present the results of an experimental and theoretical study of the gain (or absorption) experienced by a weak probe beam propagating through a sodium vapor in the presence of an intense pump field that is nearly resonant with the 3s → 3p atomic transition. The probe-transmission spectrum includes three distinct features that result from the modification of the atomic-level structure by the ac-Stark effect. Two of these features can lead to amplification of the probe wave. We measured the dependence of the probe spectrum on the detuning of the pump beam from resonance and on the pressure of a helium buffer gas. The experimentally obtained spectra are in good agreement with the predictions of a theoretical model based on the solution of the density-matrix equations of motion for a two-level atom and including the effects of Doppler broadening. The maximum gain measured in these experiments occurs at one of the Rabi sidebands and leads to a 38-fold increase in the intensity of the probe wave. Under some experimental conditions, we also observed two additional resonances, which are due to stimulated Raman scattering involving the sodium ground-state hyperfine levels.

Journal of the Optical Society of America BJan 1, 1988108 citations

Measurement of the emission and absorption spectra of strongly driven two-level atoms

Shaoul Ezekiel, F Y Wu

An investigation was made of the resonance fluorescence and absorption spectra of sodium atoms [corresponding to the 3 2 S 1/2 ( F =2)–3 2 P 3/2 ( F' =3) transition] excited by a strong monochromatic field, as well as by combinations of strong and tunable fields. The experimental results obtained were found to be in good agreement with the theoretical predictions.

Soviet Journal of Quantum ElectronicsAug 31, 19785 citations

Induced gain and modified absorption in a strongly driven sodium vapor

Mark T. Gruneisen, Kenneth R. MacDonald, Robert W. Boyd

The results of an experimental and theoretical study of the gain (or absorption) experienced by a weak probe beam propagating through a sodium vapor in the presence of an intense pump field that is nearly resonant with the 3s→3p atomic transition are presented. In general, the probe transmission spectrum is found to be comprised of three distinct features, two of which can lead to amplification of the probe wave. The origin of these features can be traced to the modification of the atomic level structure by the ac Stark effect. The experimentally measured spectra are in good agreement with the predictions of a theoretical model based on the solution of the density-matrix equations of motion for a two-level atom and including the effects of Doppler broadening. The dependence of the induced gain on the pressure of a helium buffer gas has been measured and is found to be in good agreement with the predictions of theory. The maximum gain observed in these experiments occurs at one of the Rabi sidebands and leads to a 38-fold increase in the intensity of the probe wave.

Annual Meeting Optical Society of AmericaJan 1, 19870 citations