三束相干光场驱动的Ru原子蒸汽中可调谐的光吸收

Tunable light absorption in Ru atomic vapor driven by three coherent fields

在铷原子蒸汽中,同时引入一束强相干光和两束耦合光共同作用在一个多普勒加宽的四能级N模型原子系统中。在原子系统中通过耦合场的引入以及耦合场强度的调节,观察量子光学现象。首先,由原子模型出发,由哈密顿量方程求得密度矩阵,再经由拉氏变换法求解,得出弱探测光的吸收光谱表达式。在光路设计中,采用耦合光与探测光同向,与饱和光反向传播,通过光场参数的调节,可以观察到六个相干光学烧孔和一个电磁感应光透明窗口。同时,采用了两束耦合光分别和探测光反向、同向传播,饱和光与探测光反向传播。此时在吸收光谱中,将同时出现电磁感应光透明和电磁诱导吸收两种现象。进而,在原子系统中,采用光路的不同搭配,在吸收光谱中可以观测到吸收增强或减弱情况的出现,包括形成烧孔的位置和个数的变化;通过驱动场激发原子的相干跃迁,使得在吸收谱线中同时出现电磁诱导透明和电磁诱导吸收两种吸收特性,并通过光场的调节,数据模拟的比较,分析两种量子相干效应的产生和转换,进行深入研究,并得出结论,这些结果对于现在热门的光学量子存储将有较好的理论指导。

In recent years,based on the intense interaction between coherent light and matter,the controllable quantum interference phenomena,such as coherent population trapping,electromagnetically induced transparency and electromagnetically induced absorption,optical hole-burning,have attracted a comprehensive concern.For exploring the controllable characteristics of light absorption involving the coherent hole-burning,a four-level Ntype atomic system was proposed,which was driven by a strong coherent light field and two coupling fields with the Doppler broadening thermal rubidium vapor.Via introducing the coupling fields and then adjusting the intensity of the coupling field in such an atomic system,some interesting quantum optical phenomena can be observed.Based on the design of this atomic model,the expression of absorption spectrum of the weak probe light fields was derived via the Laplace transform with the system Hamiltonian equation and density matrices.In the design of optical scheme,the saturated light field was inputted with the same or opposite propagating direction as that of the two coupling light fields,which was opposite the weak probe light field.In such a scheme,six coherent optical hole-burnings and one window based on electromagnetically induced transparency may be realized.With the adjustment of the relevant parameters in terms of the intensities and frequencies of the light fields,the enhancement or weakening of the light absorption can be realized in the absorption spectrum,including the change of the position and number of the optical hole-burning.By the transition of atoms excited by the fields,both electromagnetic induced transparency and electromagnetic induced absorption appeared at the same time.Through the adjustment of light field and the comparison of simulation results,the generation and conversion of the two quantum coherence effects were deeply studied.It is concluded that these results may have a good theoretical guidance for the popular optical quantum storage.