We study a four-level atomic scheme interacting with four lasers in a closed-loop configuration with a $\ensuremath{\diamond}$ (diamond) geometry. We investigate the influence of the laser phases on the steady state. We show that, depending on the phases and the decay characteristic, the system can exhibit a variety of behaviors, including population inversion and complete depletion of an atomic state. We explain the phenomena in terms of multiphoton interference, and compare our results with the phase-dependent phenomena in the double-$\ensuremath{\Lambda}$ scheme. This investigation may be useful for developing nonlinear optical devices, and for the spectroscopy and laser cooling of alkali-earth atoms.We study a four-level atomic scheme interacting with four lasers in a closed-loop configuration with a $\ensuremath{\diamond}$ (diamond) geometry. We investigate the influence of the laser phases on the steady state. We show that, depending on the phases and the decay characteristic, the system can exhibit a variety of behaviors, including population inversion and complete depletion of an atomic state. We explain the phenomena in terms of multiphoton interference, and compare our results with the phase-dependent phenomena in the double-$\ensuremath{\Lambda}$ scheme. This investigation may be useful for developing nonlinear optical devices, and for the spectroscopy and laser cooling of alkali-earth atoms.

arXiv:quant-ph/0207087Physical Review ANov 18, 2002103 citations

Correlated emission lasing in a four-level atomic system in the double-Λ configuration

Nadeem A. Ansari

Quantum mechanical theory of a non-degenerate correlated emission laser in a four-level atomic system in the double-Λ configuration is presented. It is shown that the mode coupling gains in this model have a phase-sensitive nature so that the spontaneous emission events in the two modes are highly correlated in such a way that the relative phase diffusion coefficient can vanish under certain conditions. Also, because of mode coupling and for a certain range of atomic population in the upper atomic levels, lasing without inversion and correlated emission take place simultaneously. Stability conditions and the steady-state modal ratio are derived and it is shown that this ratio remains stable and for this stationary value of the modal ratio both the modes amplify with equal gains.Quantum mechanical theory of a non-degenerate correlated emission laser in a four-level atomic system in the double-Λ configuration is presented. It is shown that the mode coupling gains in this model have a phase-sensitive nature so that the spontaneous emission events in the two modes are highly correlated in such a way that the relative phase diffusion coefficient can vanish under certain conditions. Also, because of mode coupling and for a certain range of atomic population in the upper atomic levels, lasing without inversion and correlated emission take place simultaneously. Stability conditions and the steady-state modal ratio are derived and it is shown that this ratio remains stable and for this stationary value of the modal ratio both the modes amplify with equal gains.

Journal of Modern OpticsJun 1, 19960 citations

Amplitude fluctuations in the two-level and four-level models of a laser

A. S. Kovalev

Radiophysics and Quantum ElectronicsJun 1, 19711 citation

Quantum interference control of a four-level diamond-configuration quantum system

Han-gyeol Lee, Hyosub Kim, Jongseok Lim +1 more

We investigate coherent control of the two-photon transition pathways of a four-level atomic system in a diamond configuration. When an ultrashort laser pulse interacts with this system in the ground state $5{S}_{1/2}$ of rubidium, the two-photon transition probability amplitude of $5{D}_{3/2}$ is obtained by a summation of all possible resonant and nonresonant two-photon transition probability amplitudes via $5{P}_{1/2}$ and $5{P}_{3/2}$ . Second-order perturbation theory predicts that the maximal constructive interference of the transition probability amplitudes occurs when the phases of eight different spectrum blocks satisfy four different phase relations. Experiments carried out with spectrally phase-coded laser pulses show good agreement with the theoretical prediction.We investigate coherent control of the two-photon transition pathways of a four-level atomic system in a diamond configuration. When an ultrashort laser pulse interacts with this system in the ground state $5{S}_{1/2}$ of rubidium, the two-photon transition probability amplitude of $5{D}_{3/2}$ is obtained by a summation of all possible resonant and nonresonant two-photon transition probability amplitudes via $5{P}_{1/2}$ and $5{P}_{3/2}$. Second-order perturbation theory predicts that the maximal constructive interference of the transition probability amplitudes occurs when the phases of eight different spectrum blocks satisfy four different phase relations. Experiments carried out with spectrally phase-coded laser pulses show good agreement with the theoretical prediction.

Physical Review ANov 27, 201318 citations

5{S}_{1/2}

of rubidium, the two-photon transition probability amplitude of

5{D}_{3/2}

is obtained by a summation of all possible resonant and nonresonant two-photon transition probability amplitudes via

5{P}_{1/2}

and

5{P}_{3/2}

. Second-order perturbation theory predicts that the maximal constructive interference of the transition probability amplitudes occurs when the phases of eight different spectrum blocks satisfy four different phase relations. Experiments carried out with spectrally phase-coded laser pulses show good agreement with the theoretical prediction.