有机材料EnBOD的放大自发发射性能研究

在紫外脉冲激光泵浦条件下,研究了有机材料EnBOD的放大自发发射(ASE)性能.EnBOD的甲苯稀溶液样品具有较窄的吸收和荧光光谱,主峰分别位于508 nm和527 nm.其ASE效率随着溶液浓度而变化,浓度为0.008 mol·L-的EnBOD样品具有最高的ASE效率,达到22.6％.其ASE主峰位于542 nm,阈值约为29.5 kW·cm-2.阈值后的ASE半宽约为12.4 nm.经紫外脉冲激光20万次泵浦后,ASE的光强衰减为初始强度的61.2％.结果表明EnBOD是一种ASE阈值较低、光稳定性良好的激光材料.     

左手介质矩形波导的吸收特性

采用微扰法研究了左手介质矩形波导的吸收特性。由于色散方程的限制,左手介质波导不能传输基模,它的吸收特性也与右手介质矩形波导明显不同。结果发现, 模式的衰减系数随长宽比(a/b)的增加而减小,而在右手介质波导中结果恰恰相反。除此之外,当不同模式的光波在同一左手介质矩形波导中传输时,每一模式都对应着相邻很近的吸收峰和吸收谷。同时高阶模的衰减系数较低阶模的大。但是,当不同模式的光波在同一右手介质矩形波导中传输时,它们的衰减曲线随着波导宽度的增加而振荡的变化,并且趋近于芯层衰减系数。另外一方面,在右手波导中,高阶模式的衰减系数较低阶模式小。     

左手材料阶跃型光纤的模场特性

从Maxwell方程组出发,讨论纤芯为左手材料,包层为右手材料阶跃型光纤,推导了矢量解的场方程.经过数学计算,求得了左手材料阶跃型光纤矢量解的特征方程.根据矢量模的分类,找到了TE模、TM模、HE模和EH模的特征方程.根据各模的特征方程,并且与右手材料光纤相关的特征方程,在靠近截止和远离截止两种情况下进行了比较,得到了左手材料光纤的某些奇异特性.     

含左手材料光纤的表面模特性

在弱导条件下,利用Maxwell方程组,对纤芯是左手材料,包层是右手材料的光纤表面模进行了研究,得到了TE (TM)、 EH和 HE表面模的色散方程,.根据色散方程,画出了相应表面模和含左手材料光纤导模的色散曲线.比较这些色散曲线,发现了含左手材料光纤表面模一些新的特性.     

Manipulation of Spontaneous Emission via Quantum Interference in an Elliptically Polarized Laser Field

Manipulation of spontaneous emission from an atom confined in three kinds of modified reservoirs has been investigated by means of an elliptically polarized laser field. Some interesting phenomena such as the multi-peak structure, extreme spectral narrowing, and cancellation of spontaneous emission can be observed by adjusting controllable system parameters. Moreover, these phenomena depend on the constructive or destructive quantum interference between multiple decay channels and which can be changed appreciably by varying the phase difference between the two circularly polarized components of the probe field. These results demonstrate the importance of an elliptically polarized laser field in controlling the spontaneous emission and its potential applications in high-precision spectroscopy.     

基于自发辐射光谱的超声速流场测速技术

等离子体状态参数测量是研究等离子体特性,开展等离子体模拟再入环境、等离子体隐身、等离子体减阻以及边界层控制等研究的重要基础.利用等离子体射流的自发辐射光谱,提出了一种基于光学多普勒频移效应的等离子体超声速射流测速的方法.首先,测量了等离子体中Ar原子产生的自发辐射光谱,选择696.54 nm的特征谱线,作为等离子体发生...     

Spontaneous Emission Originating from Atomic BEC Interacting with a Single-Mode Quantized Field

In this paper we present a general theoretical model for the interaction between a number of two-level atoms constituting Bose-Einstein condensate (BEC) and a single-mode quantized field. In addition to the usual interacting terms, we take into account interatom as well as higher-order atom-field interactions. To simplify the Hamiltonian of system, after using the Bogoliubov approximation we proceed to calculate the transformed operators of atoms and field. Then, to quantify the spontaneous emission, we get analytical expressions for the expectation value of ?_z as the atomic population inversion (API), in the cases of number and coherent states for the atomic subsystem. Our results show that the above-mentioned model interaction leads to the appearance of collapse-revival phenomenon in API. In more detail, the revival time may be tuned by adjusting the interatom interaction constant. Also, the damping process lowers the amplitude of API, but does not change the CR times for weak damping. Moreover, increasing the damping may decrease the number of CRs in a given interval of time such that no revival occurs. Briefly, it may be concluded that in the resonant case the revival times are insensitive to the change of the higher-order atom-field interaction constant and are affected only by the interatom interactions. Finally, we express that, how we can find a practical procedure to measure the quantum states of atoms in BEC.     

Spin-photon Entanglement in Spontaneous Emission

The two-pathway decay, spin-photon entanglement, and spontaneous generated spin coherence in a Lambdatype three-level system can be understood in a unified picture in terms of quantum entanglement of the electron spin, the photon polarization, and the photon waveform. Within such a unified picture, the spontaneous emission can be controlled to present a designated effect by external field, optical excitation, and quantum measurement. Various experiments are proposed to implement such control, with some of them already realized.     

各向异性色散左手材料平面波导的导模特性(英文)

对芯层为左手材料而内外包层都是普通材料的非对称三层平面波导TE振荡模进行了分析.在考虑左手材料色散和各向异性的情况下,从Maxwell方程组出发,得到了TE振荡模的色散方程和功率流分布,并且画出了相应的色散曲线.我们找到了8个TE振荡模,而且包括基模.随着模阶数的增加,模色散曲线右移,功率流曲线下移.但是,随着波导厚度的增加,色散曲线左移,功率流曲线上移.此外,TE振荡模有反常色散特性和负的群速,这正揭示了左手材料的本质特性.     

各向异性色散左手材料平面波导的导模特性

对芯层为左手材料而内外包层都是普通材料的非对称三层平面波导TE振荡模进行了分析.在考虑左手材料色散和各向异性的情况下,从Maxwell方程组出发,得到了TE振荡模的色散方程和功率流分布,并且画出了相应的色散曲线.我们找到了8个TE振荡模,而且包括基模.随着模阶数的增加,模色散曲线右移,功率流曲线下移.但是,随着波导厚度的增加,色散曲线左移,功率流曲线上移.此外,TE振荡模有反常色散特性和负的群速,这正揭示了左手材料的本质特性.     

左手材料光纤的标量解近似

从Maxwell方程组出发,讨论纤芯为左手材料,包层为右手材料的阶跃型光纤.在弱导的情况下,假定横向场的极化方向保持不变,推导了横向电场满足的Helmholtz方程,利用边界条件,经过数学计算,建立了左手材料光纤标量解的特征方程,画出了左手材料光纤LP01模和LP11模的色散曲线.比较左、右手材料光纤的特征方程及其相关曲线,得到了左手材料光纤的某些奇异特性.     

左手材料纤芯双包层光纤的传输特性

对纤芯为左手材料,内包层和外包层都为右手材料的双包层光纤进行了分析.在弱导情况下,且不考虑介质损耗,由亥姆霍兹方程出发,得到了HE、EH、TE和TM导模的色散方程,并在远离截止条件下,对其进行简化.所有的TE和TM模都是简并的.分别讨论了内包层折射率和厚度对该左手材料光纤最低阶导模的影响,画出了各自的色散曲线,并和右手材料光纤导模相应色散曲线进行了比较,发现左手材料光纤的低阶导模具有反常的色散特性.     

关于左手性介质几何光学的研究(一)

根据几何光学中的费马原理和完善成像原理研究了光线经过正负折射率界面时的传播特性,推导了单负折射率完善成像的曲面方程,讨论了单块负折射率透镜成像特性的一些缺陷及改进方案,依此指出了最短时间原理的适用范围的局限性和利用左手性介质制作光学器件的优越性,为进一步研究左手性介质的光学特性和相关光学器件设计提供了理论基础.     

Control of Spontaneous Emission from a Microwave Field Coupled Five-Level M-type Atom in Photonic Crystals

We investigate the spontaneous emission spectrum of a five-level M-type atom driven by a microwave field, in which one lower level is coupled by the same modified reservoir to two upper levels. The results show that a few interesting phenomena in spontaneous emission spectra, such as spectral-line shift, spectral-line enhancement and spectral-line suppression, which can be controlled by adjusting the proper parameters of the system. These phenomena can originate from quantum interference of the strong coupling system.     

含左手材料对称五层平面波导模场特性

对芯层为左手材料而内外包层都是普通材料的对称五层平面波导进行了探讨.得到了两类TE振荡模的色散方程,且在考虑材料色散的条件下,画出了相关模式的色散曲线.随着模阶数的增加,模色散曲线左移,它们的截止频率变小.其次,发现零阶TE振荡模的存在.除此以外,TE振荡模有三类色散特性：正常色散;反常色散;双模简并.     

含左手材料对称三层平板空气波导的模式特性

研究了左手材料作为衬底及覆盖层的对称三层平板空气波导的传输特性.快波和慢波都可以在这种波导中传播.快波不存在基模模式,只有0阶和1阶的TE或TM模才会出现慢波.当左手材料的相对介电常量和相对磁导率相等时,TE、TM模式完全简并,当其相异时简并消除.可以存在同阶模式的双传播模.     

含左手材料对称五层平面波导模场特性(英文)

对芯层为左手材料而内外包层都是普通材料的对称五层平面波导进行了探讨.得到了两类TE振荡模的色散方程,且在考虑材料色散的条件下,画出了相关模式的色散曲线.随着模阶数的增加,模色散曲线左移,它们的截止频率变小.其次,发现零阶TE振荡模的存在.除此以外,TE振荡模有三类色散特性:正常色散;反常色散;双模简并.     

Resolution Ability and Surface Bright Spots of a Lossy Left-handed Material Slab

The imaging quality of a lossy left-handed material （LHM） slab is studied. The exact solution is obtained for the interaction of a monochromatic source with a lossy LHM slab by Fourier integrals in wave number domain. It is found that a small amount of loss may have a strong suppression of the super-resolution ability. However, the resolution of a lossy slab can still be better than a conventional lens because the evanescent wave can still be partly restored if the loss is small enough. The localized field with large amplitude （surthce bright spots） near the interfaces of the slab is related to the resonance of the coupling between surface waves at the interfaces, The evanescent wave restoration and the surface bright spots are two relevant phenomena. The distance of the bright spots is close to the half of the resolution length.     

Distributional Modes for Scalar Field Quantization

We propose a mode-sum formalism for the quantization of the scalar field based on distributional modes, which are naturally associated with a slight modification of the standard plane-wave modes. We show that this formalism leads to the standard Rindler temperature result, and that these modes can be canonically defined on any Cauchy surface.     

左手系材料界面上的非线性TE电磁波

针对电磁波在非线性左手系材料中的传播性质, 分别研究了左、右手系材料界面以及两左手系材料界面上非线性TE表面波的传播行为讨论了导波的频率特性、色散关系以及群速度随频率的变化规律分析表明,两种界面上的非线性TE表面波均存在频率通带和禁带,且带宽是传播功率的函数揭示了在一定条件下,左、右手系材料界面上既可以支持正向传播的非线性TE表面波,也可以支持反向传播的非线性TE表面波;两左手系材料界面上表面波的传播性质因材料参量的变化差异较大,一定参量条件下,该界面上仅支持反向传播的非线性TE表面波.