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arXiv:1307.5649

Influence of Pulse width and Rabi frequency on the Population dynamics of three-level system in two-photon absorption process

Nam-Chol Kim, Myong-Chol Ko, Song‐Jin Im, Zhong‐Hua Hao

Published Jul 22, 2013• 0 citations
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Abstract

We investigate the population dynamics of the three-level system in the two-photon absorption (TPA) process, mainly focusing the influence of pulse width and Rabi frequency on the population dynamics of the system. We observe the dependency of the population with the Rabi frequency and the pulse width. We also show that the arbitrary superposition state consisted in two states, upper state and lower state, is possible by controlling the pulse width and Rabi frequency. The results obtained can be used to the case of more complex multilevel system and they can be valuable for coherent quantum control in quantum information processing.

DOI
10.48550/arxiv.1307.5649

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We investigate the population dynamics of the three-level system in the two-photon absorption (TPA) process, mainly focusing the influence of pulse width and Rabi frequency on the population dynamics of the system. We observe the dependency of the population with the Rabi frequency and the pulse width. We also show that the arbitrary superposition state consisted in two states, upper state and lower state, is possible by controlling the pulse width and Rabi frequency. The results obtained can be used to the case of more complex multilevel system and they can be valuable for coherent quantum control in quantum information processing.
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We demonstrate Rabi oscillation of a resonant two-photon transition in a three-level ladder-type quantum system of gaseous rubidium atoms induced by a single femtosecond laser pulse. For this, we shape the flat-top spatial profile of the laser pulse and perform the ultrafast population cycling of the atoms as a function of pulse energy. The experimental result confirms that the Rabi frequency of the transition from a ground state to a final state depends linearly on the pulse area, although the transition is a two-photon process.
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Coherent control of regions with spatial excitation of populations and coherence between two lower states in three-level $\ensuremath{\Lambda}$-type quantum systems mediated by the self-induced transparency (SIT) phenomenon is theoretically investigated with one- and two-color ultrashort pulses and with pulse sequences beyond the slowly varying envelope (SVEA) and rotating wave (RWA) approximations. The effects of different parameters characterizing the pulses and the medium on the location as well as the width of such excited regions have been studied numerically by means of the finite-difference time-domain (FDTD) method. It has been determined that with a scheme of two-pulse excitation one can effectively control the position at which the region is written and its width. In particular, the position of the excited region can be controlled by the area of the pulses. We find that the maximum value of the population transferred to the lower excited state depends on the detuning of the pulses with respect to the one-photon resonances, and that both position and width of the region also depend on the temporal duration of the pulses. We show how after the excited region is written, its position can be shifted by additional pulses. On the basis of numerical results, scaling laws are formulated for the reported phenomena. With such control, the width of the region excited inside the medium can be reduced to the order of the wavelength of the light.