基于电磁感应透明技术,通过求解原子的密度矩阵方程和电磁场的传输矩阵方程,研究了被行波场和驻波场共同耦合的一个四能级冷原子介质的稳态光学特性,发现在特定参数下能够产生一个几乎完美的双光子带隙结构,在这两个光子带隙对应的频率区域内反射率都均匀地超过95%.通过改变耦合场的强度和频率,可以方便地调节这两个光子带隙的位置和宽度.这一双光子带隙结构可用来实现全光路由和全光开关,有望在全光信息网络中获得应用.%By using the technique of electromagnetically induced transparency and solving density matrix equations for atoms and transfer matrix equations of fields, we study the steady optical properties of a four-level system of cold atoms driven by a traveling-wave field and a standing-wave field. It is found that a nearly perfect structure of double photonic band-gap can be generated with specific parameters. In particular, the reflectivity inside each photonic band-gap is homogeneous over 95%. It is convenient to modulate the positions and widths of both photonic band-gaps by changing intensities and frequencies of the driving fields. The double photonic band-gaps can be used to achieve all-optical routing and switching and therefore may have applications in all-optical information networks.
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