基于驻波耦合EIT的静态光形成机制以及Goos-Hanchen效应

The mechanism of the stationary light based on the standing wave coupled electromagnetically induced transparency (EIT) is normally treated as the photonic band-gap (PBG) or the four-wave mixing (FWM). It is reasonable because both of the phenomena can result in the effective reflection. However, those two are very different. For example, if the atomic density is a litter lower, the PBG will not be created. In this project, we will discuss the contribution of PBG and the FWM for an angle of the atomic density. Considering that the atomic density is rising from a quite low point, the reflection based on PBG will get stronger as well. We will try to systemically describe such growing process of the reflectivity and define a critical point for the atomic density when the contribution of the PBG should be taken into account. The research is quite important for understanding the stationary light as well as the other phenomena that based on the standing wave coupled EIT. Another content that included in the project is the Goos-Hanchen (GH) effect based the standing wave coupled EIT. Since the PBG is tunable in such medium, the GH effect is tunable as well. The relation between the GH shift and the strength as well as the frequency of the standing wave will be analyzed. Such tunable effect with a fixed configuration is very promising for the integrated optics.

基于驻波耦合电磁感应光透明(EIT)效应的静态光现象的形成机制被认为是光子晶体或四波混频. 其合理性在于这两种效应都可以实现反射; 但它们却是两种完全不同的物理现象. 在本项目将从介质的粒子数密度的角度, 探讨这两种现象对于光子反射的贡献. 我们将在Rb87原子中的三能级Lambda模型中分析粒子数密度由低到高的变化过程中, 光子晶体从无到有, 不断增强的过程; 包括反射谱在这一过程中的渐变情况, 以及光子晶体起作用时的粒子数临界大小. 本内容的研究对于理解静态光(以及其它基于驻波耦合EIT效应的物理现象)的形成机制有重要意义. 本项目的另一个研究内容是基于驻波耦合EIT的Goos-Hanchen(GH)效应. 分析在可调谐的光子禁带中的GH效应的可调谐性;明确GH位移对(驻波)耦合场的强度和频率的依赖关系.这种固定结构的可调节GH效应在集成光学领域很有应用价值.

本项目中, 我们主要研究了光反射现象中非镜面效应的相干调控以及驻波场驱动的原子介质中的可调谐光栅等问题. 非镜面效应包括Goos-Hanchen (GH)偏移, 以及Imbert-Fedorov (IF)偏移. 对于GH偏移, 我们在双色驻波场驱动的四能级双Lambda系统中展开. 分析了线性和非线性GH偏移对系统参数的依赖关系. 同时, 我们也考虑了热原子气体中的多普勒效应, 以及有限的光束截面对GH效应的影响. 控制IF偏移的研究工作主要针对无吸收高折射介质展开. 我们在一个三能级Lambda系统中引入一个微波场耦合两个基态能级, 从而实现了无吸收高折射介质. 研究发现, 这一类介质的无吸收状态可以导致较强的IF偏移. 我们系统地讨论了IF偏移对光场相位, 以及微波场强度的依赖关系. 非镜面效应的相干调控在高灵敏温度探测, 化学气体探测, 生物传感等方面有重要的应用价值. 另外, 静态光形成机制的研究仍在进行中, 目前我们着重探讨了驻波场驱动的原子系统对光的调控机制, 着重研究了三能级系统中的相干粒子数震荡, 以及基于此的可调谐光栅的反射率问题.