共查询到20条相似文献,搜索用时 93 毫秒
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本文利用一维有限光子晶体的模函数展开场算符,确定光与物质相互作用的Hamilton量,从而得到两能级原子自发辐射衰减的动力学方程。未借助马尔科夫近似,我们用数值计算的方法直接求解了原子与场随时间演化的动力学方程,发现在自发辐射过程的最初几个光学周期的时间内,自发衰减速率随时间的变化存在一系列脉冲形状的峰。由于作用于原子的场是一维光子晶体中历经多重反射的场的相干迭加的结果,原子的衰减行为敏感地依赖于多重反射场在原子所在位置的干涉。这种干涉性质依赖于光子晶体的结构。改变光子晶体的结构,使原子的跃迁频率位于光子晶体的禁带中、导带中或缺陷模频率处,可使原子的自发辐射得到抑制或增强。 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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单一原子(分子)的自发辐射衰变的动力学性质强烈地依赖于其在光子晶体中的位置及其辐射偶极矩与所处位置场的相对方向.测量单一原子(分子)的自发辐射衰变特性只能反映光子晶体的局域态密度特征,而不能反映光子晶体的全态密度特征.理论上研究发现,通过引入含不同密度分布的发光分子可以探测到光子晶体的全态密度的部分细节甚至全部信息.按来源首次将全态密度分为两个部分,证明了特定的发光分子分布可以完善地反映其中的一部分或者全部,这为解释、设计加速或抑制原子(分子)自发辐射的实验提供了有益的指导.
关键词:
光子晶体
自发辐射
态密度
密度分布 相似文献
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研究了动态各向同性光子晶体中二能级原子自发辐射的性质,主要讨论了光子晶体能带带边频率随时间作阶跃调制和三角函数周期调制两种情况下,原子上能级占据数随时间的演化特性.当光子晶体能带带边频率随时间作阶跃调制时,原子上能级占据数随时间的演化不仅和上能级与能带带边的相对位置δ有关,更依赖于阶跃调制发生的时刻.调制发生时刻不同,调制后原子上能级占据数随时间的演化也不同.当光子晶体能带带边频率随时间作三角函数周期调制时,二能级原子上能级占据数随时间作总体衰减的准周期振荡.通过选择调制频率和调制初相位可调控准周期振荡的频率、峰值与谷值的大小以及占据数的总体衰减速度等. 相似文献
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研究了双带型光子晶体中双V型四能级原子自发辐射的辐射谱.双V型四能级原子同时与真空热库和双带型光子晶体热库耦合.研究发现双V型四能级原子自发辐射谱中有三种不同原因可能引起的黑线:第一种是由于量子干涉效应;第二种是由于各向同性光子晶体带边处态密度具有奇异性;第三种是真空场中的量子干涉和光子晶体禁带内态密度为零共同作用的结果.通过移动光子晶体的带边位置,在各向同性光子晶体带边引入光滑因子,以及在光子晶体中引入缺陷等对这三种黑线的影响,对上述结果进行了分析和讨论.
关键词:
双带型光子晶体
双V型四能级原子
黑线 相似文献
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A model of the propagation of a quantized electromagnetic field in a one-dimensional photonic crystal that contains two-level atoms that interact with the field is proposed. The model separately considers the interaction of the quantized radiation with the quantum system and with the photonic crystal. The use of the model is exemplified by its application to the study of the decay of excited states of one- and two-level atoms placed in the photonic crystal. The possibility of the transformation of the front of a single photon by a finite dielectric is demonstrated. 相似文献
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Spontaneous decay behaviors from an assembly of atoms (or molecules) in 3D photonic crystals (PC's) with pseudogaps are investigated. Theoretically, a lifetime distribution function for these atoms or molecules is defined to reveal decay kinetics. Our calculations show that quite wide or narrow lifetime distributions can occur for different spread configurations of the atoms (or molecules). The pure PC effect may lead to coexistence of both accelerated and inhibited decay processes. These results provide theoretical clarification for substantial discrepancies in the recent reported experiments. 相似文献
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Spontaneous emission from GaAs/AlGaAs quantum dots (QDs) embedded in photonic crystals with a narrow photonic band gap is studied theoretically. The results show that the decay lifetime is very sensitive to the sizes of QDs, and both inhibited and accelerated emission can occur, which had been indicated in a previous experiment. The Weisskopf–Wigner approximation, good for atoms and molecules, may be incorrect for QDs. A damped Rabi oscillation of the excited state with the transition frequency outside the photonic band gap may appear, which is impossible for atoms and molecules. 相似文献
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Spontaneous emission behavior from atoms (or molecules) in one-dimensional photonic crystal with a defect is investigated. Taken all the TE and TM modes into account, the normalized spontaneous emission rate of the atom is calculated as a function of the position of the atom in the crystal. Results for both nonabsorbing dielectric structure and absorbing dielectric structure are presented. With the increase of the thickness of the defect in which the atoms are embedded, the oscillations of the spontaneous emission rate versus the position of the atom become dense and the lifetime distribution becomes narrow and sharp. The PC effect may lead to the coexistence of both accelerated and inhibited decay processes. 相似文献
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M. Konôpka V. Bužek 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(2):285-293
We propose a method for entangling a system of two-level atoms in photonic crystals. The atoms are assumed to move in void
regions of a photonic crystal. The interaction between the atoms is mediated either via a defect mode or via a resonant dipole-dipole interaction. We show that these interactions can produce pure entangled atomic states. We analyze the problem with parameters typical
for currently existing photonic crystals and Rydberg atoms and we show that the atoms can emerge from photonic crystals in
entangled states. Depending on the linear dimensions of the crystal we estimate that a pair of atoms entangled in a photonic
crystal can be separated by tens of centimeters.
Receive 11 June 1999 and Received in final form 4 October 1999 相似文献
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Sun HB Xu Y Juodkazis S Sun K Watanabe M Matsuo S Misawa H Nishii J 《Optics letters》2001,26(6):325-327
We used voxels of an intensely modified refractive index generated by multiphoton absorption at the focus of femtosecond laser pulses in Ge-doped silica as photonic atoms to build photonic lattices. The voxels were spatially organized in the same way as atoms arrayed in actual crystals, and a Bragg-like diffraction from the photonic atoms was evidenced by a photonic bandgap (PBG) effect. Postfabrication annealing was found to be essential for reducing random scattering and therefore enhancing PBG. This technique has an intrinsic capability of individually addressing single atoms. Therefore the introduction of defect structures was much facilitated, making the technique quite appealing for photonic research and applications. 相似文献
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We propose a concentration scheme of the W class state via cavity QED technique. In our scheme the influences of cavity decay and atomic spontaneous emission have been considered. Furthermore, the atomic spontaneous emission has been suppressed by using non-radiative transitions in atoms with three-level structure, and the photonic qubit is used as flying qubit and atomic qubit as stationary qubit. Therefore our scheme is comparatively easy to realize within techniques presently available. 相似文献
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Yaping Yang Xianshan Huang Shi-Yao Zhu 《量子光学学报》2006,12(B08):69-70
The measurement-induced suppression and acceleration effects on A-type atomic decay in three-dimensional anisotropic photonic crystals are investigated. We consider the two cases, only one or both of the two atomic resonant frequencies being near the band edge of a photonic crystal. Due to the deformation of the electromagnetic density of states, the repeated projection onto the excited state can lead to decay suppression or acceleration effect already at rather low repetition rates. Such measurement-induced effects are dependent on the frequency of measurements and the relative position of the atomic upper level from the band edge of photonic crystals. The behaviors of instant and effective decay rates are studied in detail, which are different from the case of isotropic photonic crystals. 相似文献
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《中国物理快报》2016,(7)
We discuss the evolution dynamics of a quantum system consisting of two two-level atoms separately embedded within two strongly coupled photonic crystal cavities.Although the quantum system is subjected to dissipation and decoherence from the cavity leakage and the atomic decay,it does allow for eigenstates that are not influenced by one of the two dissipation channels and results in dissipation-inhibition quantum states.These dissipationfree quantum states can help to achieve an extremely long photon and atom storage lifetime and provide a new perspective to realize efficient quantum information storage via reducing the negative influence of the dissipation from the environment. 相似文献