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Physical Review A

Photoassociation dynamics driven by a modulated two-color laser field

Wei Zhang, Zeyu Zhao, Ting Xie, Gao‐Ren Wang, Yin Hui Huang, Shu‐Lin Cong

Published Nov 16, 2011• 13 citations
Publisher

Abstract

Photoassociation (PA) dynamics of ultracold cesium atoms steered by a modulated two-color laser field $\phantom{\rule{4pt}{0ex}}E(t)={E}_{0}f(t)\mathrm{cos}(\frac{2\ensuremath{\pi}}{{T}_{p}}\ensuremath{-}\ensuremath{\varphi})\mathrm{cos}({\ensuremath{\omega}}_{L}t)$ is investigated theoretically by numerically solving the time-dependent Schr\"odinger equation. The PA dynamics is sensitive to the phase of envelope (POE) $\ensuremath{\varphi}$ and the period of the envelope ${T}_{p}$, which indicates that it can be controlled by varying POE $\ensuremath{\varphi}$ and period ${T}_{p}$. Moreover, we introduce the time- and frequency-resolved spectrum to illustrate how the POE $\ensuremath{\varphi}$ and the period ${T}_{p}$ influence the intensity distribution of the modulated laser pulse and hence change the time-dependent population distribution of photoassociated molecules. When the Gaussian envelope contains a few oscillations, the PA efficiency is also dependent on POE $\ensuremath{\varphi}$. The modulated two-color laser field is available in the current experiment based on laser mode-lock technology.

DOI
10.1103/physreva.84.053418

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Photoassociation (PA) dynamics of ultracold cesium atoms steered by a modulated two-color laser field E(t)=E0f(t)cos(2\ensuremathπTp\ensuremath−\ensuremathφ)cos(\ensuremathωLt)\phantom{\rule{4pt}{0ex}}E(t)={E}_{0}f(t)\mathrm{cos}(\frac{2\ensuremath{\pi}}{{T}_{p}}\ensuremath{-}\ensuremath{\varphi})\mathrm{cos}({\ensuremath{\omega}}_{L}t)E(t)=E0​f(t)cos(Tp​2\ensuremathπ​\ensuremath−\ensuremathφ)cos(\ensuremathωL​t) is investigated theoretically by numerically solving the time-dependent Schr"odinger equation. The PA dynamics is sensitive to the phase of envelope (POE) \ensuremathφ\ensuremath{\varphi}\ensuremathφ and the period of the envelope Tp{T}_{p}Tp​, which indicates that it can be controlled by varying POE \ensuremathφ\ensuremath{\varphi}\ensuremathφ and period Tp{T}_{p}Tp​. Moreover, we introduce the time- and frequency-resolved spectrum to illustrate how the POE \ensuremathφ\ensuremath{\varphi}\ensuremathφ and the period Tp{T}_{p}Tp​ influence the intensity distribution of the modulated laser pulse and hence change the time-dependent population distribution of photoassociated molecules. When the Gaussian envelope contains a few oscillations, the PA efficiency is also dependent on POE \ensuremathφ\ensuremath{\varphi}\ensuremathφ. The modulated two-color laser field is available in the current experiment based on laser mode-lock technology.
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The formation of ultracold Cs 2 molecules via photoassociation (PA) with a spectral π-jump laser pulse is theoretically investigated by solving the time-dependent Schrödinger equation using the mapped Fourier grid method. Numerical calculations show that the population distributions of associated molecules mainly result from the off-resonant excitation of the π-jump laser pulse. Compared with the transform-limited pulse, an efficient population accumulation in the PA process is achieved with the π-jump pulse. An oscillation pattern appears in the population on the vibrational levels of the state owing to the action of the post-half-pulse in the π-jump pulse. The PA efficiency is related to the Rabi angle of the laser pulse. A π-jump pulse can be used to enhance more effectively the PA efficiency than a transform-limited pulse with the same Rabi angle.
This paper presents calculation results for the photoassociation of a NaK molecule with a two-color modulated laser and gives a detailed analysis about them. For the two-step photoassociation process in intense fields, the effect of two-color modulated laser parameters, such as relative phase, envelope period, and laser intensity, on the population of the molecular electronic state can be obtained by solving the time-dependent Schrödinger equation through the quantum wave packet method. The numerical simulation shows not only that the influence of laser parameters on the vibrational distribution presents some regularity, but also that a higher population in the ground electronic state can be realized through adjusting these laser parameters.
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