共查询到18条相似文献,搜索用时 62 毫秒
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利用电磁感应透明技术,在一维光晶格中相干驱动四能级Lambda模型冷原子系统,从而实现动力学可调谐电磁感应光子带隙结构。基于两邻近能级间的自发辐射相干(SGC)效应,通过控制耦合场从远共振到共振,使该原子系统实现从两个光子带隙转变为三个光子带隙的动态过程。当自发辐射相干效应不存在时,在探测场共振区域处探测光子被原子系统强烈吸收,因此感应光子带隙严重形变甚至无法形成。通过数值计算证明光子带隙结构的形成源自于自发辐射相干效应下探测场和耦合场之间的三阶交叉克尔(Kerr)非线性调制,并且通过控制耦合场的耦合方式,可以实现系统从两个光子带隙到三个光子带隙的动力学调控。 相似文献
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研究了由两个垂直传播的强驻波激光场共同耦合的一个四能级Tripod型冷87Rb原子介质的稳态光学响应特性. 结果发现, 当两驻波场满足双光失谐条件时, 可在这两驻波场的传播方向上同时获得反射率高达95%以上的电磁感应光子带隙结构; 通过适当调节强激光场, 还可实现一个方向为光子带隙而另一个方向为透明窗口或者两个方向均为透明窗口的结构. 并且光子带隙和透明窗口的频宽和位置是可调谐的. 这种全光控制的二维的信号光禁闭和导通机制可用于实现全光开关和全光路由, 有利于复杂的全光通讯网络的开发.
关键词:
相干诱导光子带隙
电磁感应透明
周期调制原子相干 相似文献
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赝带隙光子晶体中原子集合的自发辐射动力学 总被引:2,自引:0,他引:2
介绍了三维赝带隙光子晶体中原子集合的自发辐射衰减分布特性,发现不同的原子集合弥散组态,其原子自发辐射呈现十分宽或窄的有限的寿命分布,纯粹光子晶体效应可导致加速和抑制衰减过程并存,从理论上揭示了现有的实验结果的重大分歧的缘由。 相似文献
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我们对两类光学材料-光子晶体及左手材料中的量子相干效应进行了理论研究。光子带隙材料通常是指人工制作的具有光子通带和禁带的光学材料,它可以用来控制光场的传输及某些微观过程。光子晶体是典型的光子带隙材料,光子晶体的周期性结构导致其中的原子的量子光学性质与自由空间中明显不同,例如出现光局域化与原子自发辐射的抑制、光子-原子束缚态、二能级原子布居数囚禁等现象。最近的研究还表明心,特殊的态密度分布会导致感应透明现象,使得原子对与其共振的探测光场的吸收趋于零。这与电磁感应透明(EIT)类似,但不需要外加耦合场来建立相干。我们系统地研究了光子晶体特殊态密度产生的量子相干效应,包括三能级系统的感应透明、无反转增益、光速减慢等,及四能级系统的自发辐射和光开关效应,发现强的量子相干效应导致原子辐射与吸收性质产生多方面的改变。 相似文献
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论证了在赝带隙光子晶体中存在一个全频率域态总数守恒规则,在完全带隙光子晶体中还存在一个局域态总数守恒规则.态总数守恒规则指出,如果一个光子晶体的态密度在某些频率范围存在相对于等效介质态密度的谷,则一定由其他频率范围内相对于等效介质态密度的峰来补偿.使用符合态总数守恒规则的态密度模型,解释了态密度调制导致的自发辐射谱增强、抑制、变窄、红移、蓝移以及谱分裂等光子晶体中的量子光学现象.该理论比较适合研究在具有赝带隙的光子晶体中大量随机分布的发光原子或分子的自发辐射行为.
关键词:
光子晶体
自发辐射
态密度
光子赝带隙 相似文献
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This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence (SGC). It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags π/2 than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always 2π; the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence. 相似文献
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Zhen-Kun Wu Kai-Ge Chang Yi Hu Yun-Zhe Zhang Zi-Hai Jiang Yan-Peng Zhang 《Frontiers of Physics》2014,9(5):665-670
The dressed four-wave mixing (FWM) in a four-level S5Rb atomic system, experimentally demon- strated in this paper, is comprised by two coexisting processes. One is emission signal due to enhanced nonlinear via electromagnetically induced transparency (EIT). The other is the Bragg reflection of probe beam because of the created photonic band gap (PBG), which is affected by both linear and third-order nonlinear susceptibility. Moreover, we have demonstrated that different experimental parameters can significantly influence the measured signal with flexibly controlled PBG. These studies are found useful for understanding the fundamental mechanisms in generated FWM processing. 相似文献
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We investigate the reversible storage of a weak single-mode light signal in a Λ-type three-level atomic system with spontaneously generated coherence (SGC) and pumped by an incoherent field.The scheme is phase-dependent.If the phase of the controlling field is set oppositely to that of the signal field,the combination of SGC with weak pump overcomes the drawback of incompletely retrieval in the conventional scheme,leading to 100% retrieval fidelity or even to the amplification of the retrieved signal with respect to its initial one. 相似文献
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We present a comparative study of the control of-group velocity in three-level atomic systems including $\Lambda{}$-, Ladder-, and-V-types via spontaneously generated coherence (SGC) and relative phase of laser-fields. In the steady regime, expressions of group index are derived as an-analytical function of controllable parameters related to SGC and relative phase.-It is shown that the group velocity can be further slowed down or speeded up-under SGC in which modifications of group velocity due to the SGC in $\Lambda{}$--and V-systems are stronger than that in Ladder-system. In particular, when-interference strength of SGC p increases from 0.7 to 1.0, the light-propagation is switched from superluminal to subluminal modes (for $\Lambda{}$--and Ladder-systems) or from subluminal to superluminal modes (for V-system). In-the presence of relative phase, the group velocity changes between subluminal and-superluminal modes with a period of 2$\pi{}$. In resonant region, the largest-positive value of group index reaches at the relative phase $\varphi{}$ = $\pi{}$-while the largest negative value of group index reaches at $\varphi{}$ = 0 and-2$\pi{}$ for the $\Lambda{}$- and Ladder-systems, otherwise, for the V-system the-largest positive group index occurs at $\varphi{}$ = 0 and 2$\pi{}$, and the largest-negative group index occurs at $\varphi{}$ = $\pi{}$. 相似文献
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WANG Chun-liang 《中国光学》2010,3(1):11-26
Spontaneously Generated Coherence(SGC) refers to a kind of quantum coherence induced by the process of spontaneous emission. It can greatly affect the dynamics of a quantum system, and accounts for a variety of important phenomena. Many efforts have been devoted to this topic, aiming to investigate the essence of quantum coherence and advanced technologies. However, the existence of SGC needs rigorous requirements which can hardly been fulfilled in atoms placed in a free space. Therefore we must give particular considerations to investigate this coherence experimentally. In this paper, a few interesting phenomena related to SGC are summarized, such as gain without inversion, coherent population trapping, phase sensitive spec- tra, and modifications of absorption, emission, and refraction. We also review the investigations on the reali- zation of SGC, such as modifying the vacuum, coupling levels with static fields, simulating SGC with coherence induced by coherent fields, and studying SGC in special materials. 相似文献
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The modal characteristics of planar waveguides with photonic band gap guiding properties are studied. It is demonstrated that a slight deviation from the periodicity in the photonic band gap multilayers can result in multimode transmission within the guiding layer. Possible applications of the results for avoiding single mode regime destruction due to fabrication process imperfection, as well as for designing such waveguides for conventional and emerging new applications of multimode photonic devices, are pointed out. 相似文献