共查询到18条相似文献,搜索用时 109 毫秒
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反常色散介质“超光速”现象研究的新进展 总被引:2,自引:0,他引:2
文章介绍了王力军等人的光脉冲在反常色散介质传播实验的测量结果,说明了实验测量的不完全性,因而它不能在是否超光速的问题的答案,文章还介绍了近一年来相应的理论研究工作,文章作者依据物理概念和理论研究结果论证了该实验所得的负群速度本身并不超光速;如果把负群速度看成是某种能量的传播那私超光速出现在负群速度开始时间间,因而它是超距作用,违反能量守恒或动量守恒,因此,负群速度只是表观速度,能流的研究结果也证明了这一点。这就是说,该实验并没有观察 到超观察到超光速传播。 相似文献
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运用数值模拟方法讨论了控制场的变化对M型五能级原子系统相对于探测场的吸收和色散等光学性质的影响.结果表明,改变控制场拉比频率时,系统的吸收和色散性质会发生规律性变化.在特定区域会呈现电磁感应透明窗口,其中透明窗口的数量与外加控制场数目成正比,而透明窗口宽度与拉比频率大小相关,拉比频率越大,透明窗口越平坦,当拉比频率减小,透明窗口变窄同时介质色散增强可获得慢光速光脉冲. 相似文献
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通过求解全波矢布洛赫方程研究了两能级原子与飞秒超快激光脉冲的相互作用过程,计算了不同拉比频率取值下原子所受光学偶极力和粒子数布居随时间的演化情况,分析了光场失谐量对光学势分布情况的影响.研究发现:由飞秒激光场产生的横向光力的时间平均值并不等于零,而是随着拉比频率的增加呈现振荡的增大趋势;纵向光力的时间平均作用也并非是拉比频率的单调函数,而是随着拉比频率的增加呈现周期性的振荡分布特性;光学势的分布对光场的失谐量具有明显的依赖性,随着失谐量的变化,光学势的性质也随之发生了改变. 相似文献
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利用飞秒脉冲自相关技术研究了高质量三维胶体光子晶体中的慢光速和超光速效应.实验中使用的胶体光子晶体是采用压力控制的绝热沉积技术(PCIHVD)制备的、由聚苯乙烯小球组成的人工蛋白石结构.由于其中的缺陷和位错密度很低,它们具有很高的通带透过率和陡峭的能带边缘.测量了从通带到带边直至带隙中央群速度的变化,在只有20层左右小球的样品中观察到低至0.43c的慢光速以及高至1.34c的超光速现象.此外,利用时域有限差分(FDTD)方法对短脉冲在三维光子晶体中的群速度进行了数值模拟,并且和
关键词:
三维胶体光子晶体
慢光速
超光速
脉冲自相关 相似文献
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Eu3+:Y2SiO5晶体中电磁感应透明及群速度减慢研究 总被引:2,自引:2,他引:2
利用光与物质相互作用的密度矩阵方程及其数值解研究了Eu3 :Y2SiO5晶体中一种A型的电磁感应透明(EIT)和群速度减慢(SGV),得到了探测场的透射率随着探测场的失谐与耦合场的拉比频率的变化关系.分析了自旋子能级非均匀线宽及光学跃迁非均匀线宽对电磁感应透明和群速度减慢的影响,这两个线宽的增加不同程度地抑制了电磁感应透明.根据浓度与非均匀线宽的关系发现中心透射率不是随着浓度的增加而单调变化,而是存在一个最佳浓度使电磁感应透明的效果更加明显.分析表明对某一耦合场强,光群速度存在一极小值. 相似文献
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M. Sahrai 《Laser Physics》2007,17(2):98-102
We propose a scheme to localize an atom in a three-level A-type configuration inside a classical standing wave field conditioned upon the measurement of frequency of a weak probe field. Inside the classical standing wave field, the interaction between atom and the field is position-dependent due to the Rabi frequency of the driving field; hence, as the absorption frequency of the probe field is measured, the position of an atom inside the classical standing wave field will be determined. Localizing of an atom via absorption spectrum occurs during its motion inside the standing wave field. An investigation of the probe field frequency shows that the degree of localization depends on interaction parameters such as detuning, phase difference between applied fields, and Rabi frequency of the driving field. 相似文献
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Influence of Doppler broadening and spontaneously generated coherence on propagation effect in a quasi lambda-type four-level system 下载免费PDF全文
In this paper we study influences of Doppler broadening, spontaneously generated coherence, and other system parameters on propagation effect in a quasi lambda-type four-level atomic system. It is shown that when the Doppler broadening is present, generally speaking, the values of gain and intensity of lasing without inversion (i.e. the probe field) in the co-propagating probe and driving fields case are much larger than those in the counter-propagating case; considerably larger gain and intensity of lasing without inversion than those without the Doppler broadening can be obtained by choosing appropriate values of the Doppler broadening width and spontaneously generated coherence strength. The gain and intensity of lasing without inversion increase with the increase of spontaneously generated coherence strength; when spontaneously generated coherence is present, much larger gain and intensity of lasing without inversion than those in the case without spontaneously generated coherence can be obtained. Choosing suitable values of the probe detuning, Rabi frequencies of the driving and pump fields at the entrance of the medium also can remarkably enhance the gain and intensity of lasing without inversion. 相似文献
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We investigate the nonlinear light propagation in InAs/InGaAs quantum-dot-in-a-well semiconductor optical amplifiers in the limit of strong optical excitation where Rabi oscillations are excited in the active medium. The amplifier is analyzed in a degenerate four-wave-mixing setup and characterized by its frequency conversion and creation performance. Our simulations show that the interplay between the nonlinear four-wave-mixing process and the coherent Rabi oscillations greatly influences the frequency conversion process. Rabi oscillations can be resonantly excited by the correct choice of the frequency detuning between pump and probe signals, which greatly enhances the nonlinear frequency conversion efficiency at frequencies up to several THz. We furthermore show that the coherent pulse shaping of ultrashort optical pulses in the quantum-dot medium can greatly enhance their spectral bandwidth, potentially allowing for ultra-broad-band frequency comb generation. 相似文献
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The quantum fluctuation spectra of phase quadratures of the fluorescent light from a coherently driven two-level atom damping in a common vacuum is investigated. We find that by optimally choosing the Rabi frequency of the driving field, detuning between the atom and the driving field, and phase of the local oscillator the strong sideband squeezing in the spectrum of the optimal phase quadrature can be created and the degree of squeezing in the sidebands can reach about 56%. 相似文献
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Clifford M. Krowne 《Physics letters. A》2008,372(21):3926-3933
A three-level atomic system, configured as either a gaseous medium or a solid state material, with a driving field establishing a Rabi frequency of control, is tested by a probe field. The medium has bianisotropic microscopic polarizability and magnetizability, from which the permittivity and permeability tensors are derived. Non-isotropy and polarization dependence for left-handedness (negative index of refraction) is demonstrated through examination of tensor components in the detuning frequency spectrum. These results have important implications for use in optical or electronic devices. 相似文献
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<正>We study the lasing without inversion in a four-level diamond configuration in the case of incoherent pumping field within the framework of the bare-state basis.With the strong fields limit,we obtain the approximate steady-state solution,and discuss the dependence of population distribution and system gain on probe detuning and auxiliary field Rabi frequency. 相似文献
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《理论物理通讯》2017,(6)
It is well known that an optical trap can be imprinted by a light field in an ultracold-atom system embedded in an optical cavity,and driven by three different coherent fields.Of the three fields coexisting in the optical cavity there is an intense control field that induces a giant Kerr nonlinearity via electromagnetically-induced transparency,and another field that creates a periodic optical grating of strength proportional to the square of the associated Rabi frequency.In this work elliptic-soliton solutions to the nonlinear equation governing the propagation of the probe field are considered,with emphasis on the possible generation of optical soliton trains forming a discrete spectrum with well defined quantum numbers.The problem is treated assuming two distinct types of periodic optical gratings and taking into account the negative and positive signs of detunings(detuning above or below resonance).Results predict that the competition between the self-phase and cross-phase modulation nonlinearities gives rise to a rich family of temporal soliton train modes characterized by distinct quantum numbers. 相似文献