Abstract Absorption and refraction of the inner transition F2$\leftrightarrow$ F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1 $\leftrightarrow$ F3 and F2 $\leftrightarrow$ F4 are resonantly interacted with drive field with frequency $\omega$c and Rabi frequency $\varOmega$c, and saturation field with $\omega$s and $\varOmega$s, respectively. For the suitable Rabi frequencies $\varOmega$c and $\varOmega$s, we obtain the Mollow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F3 and simultaneously the saturation field takes the atom out of the lower level F2, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of $\varOmega$s. Finally, the refractive index enhancement is predicted for a wide spectral region.
Received: 23 March 2006
Revised: 03 August 2006
Accepted manuscript online:
Fund: Project supported by the
National Natural Science Foundation of China (Grant Nos 10334010
10304001, 10521002, 10434020, 10328407 and 90501007).
Cite this article:
Wang Kai(王凯), Gu Ying (古英), and Gong Qi-Huang(龚旗煌) Stimulated emission and multi-peaked absorption in a four level N-type atom 2007 Chinese Physics 16 130
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