共查询到20条相似文献,搜索用时 31 毫秒
1.
The extinction, integrated scattering, and absorption spectra of gold and silver nanorods with random and regular orientation are studied. The calculations are performed for spheroids, circular cylinders, circular cylinders with hemispherical ends (T-matrix method), and rectangular prisms (discrete dipole approximation). A new quadrupole resonance is discovered that arises between the usual plasmon dipole resonances excited by a field longitudinal or transverse with respect to the symmetry axis. The new resonance can be excited only by a TM incident wave and is the greatest for orientation of the symmetry axis of the particle at an angle of 54° with respect to the light beam. 相似文献
2.
Intersubband resonances in a semiconductor quantum well (QW) display fascinating features involving various collective excitations such as Fermi-edge singularity (FES) and intersubband plasmon (ISP). Using a density matrix approach, we treated many-body effects such as depolarization, vertex correction, and self-energy consistently for a two-subband system. We found a systematic change in resonance spectra from FES- to ISP-dominated features, as QW width or electron density is varied. Such an interplay between FES and ISP significantly changes both line shape and peak position of the absorption spectrum. We found that a cancellation of FES and ISP undresses the resonant responses and recovers the single-particle features of absorption for semiconductors with a strong nonparabolicity such as InAs, leading to a dramatic broadening of the absorption spectrum. 相似文献
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4.
Inelastic light scattering by a two-dimensional system of electrons in a conduction band with Rashba spinorbit coupling is
studied theoretically for the resonance case where the frequencies of the incident and scattered light are close to the effective
distance between the conduction band and spin-split band in a III–V semiconductor. It is shown that, in contrast to the case
of no spin-orbit coupling, the spectrum of the scattered light exhibits a plasmon peak even for strictly perpendicular polarizations
of the incident and scattered light. There exists a configuration where the scattering spectrum exhibits features originating
from single-particle transitions only. Furthermore, it is shown that, for the general case of elliptic polarizations of the
incident and scattered light, the amplitude of the plasmon peak depends on the sign of the effective Rashba spinorbit coupling
constant and the signs of the phases of the polarization vectors. This fact can be used to determine the sign of the Rashba
constant. 相似文献
5.
Light scattering by a small spherical particle with a low dissipation rate is discussed based upon the Mie theory. It is shown that if close to the plasmon (polariton) resonance frequencies the radiative damping prevails over dissipative losses, sharp giant resonances with very unusual properties may be observed. In particular, the resonance extinction cross section increases with an increase in the order of the resonance (dipole, quadrupole, etc.); the characteristic values of electric and magnetic near fields for the scattered light are singular in the particle size, while energy circulation in the near field is rather complicated, so that the Poynting vector field includes singular points whose number, types, and positions are very sensitive to fine changes in the incident light frequency. The results may provide new opportunities for a giant, controlled, highly frequency-sensitive enhancement and variation of electromagnetic field at nanoscales. 相似文献
6.
Cuiman Ma Ruifeng Zhang Jiunn-Woei Liaw Jui-Ching Cheng 《Applied Physics A: Materials Science & Processing》2014,115(1):31-37
The scattering, absorption, and extinction cross sections of Ag nanobox, nanocage, and nanoframe illuminated by a polarized plane wave are studied using the finite element method. Our numerical results show that the plasmon modes (dipole and quadrupole modes) of a single Ag nanocage are red-shifted as the thickness of the wall decreases. In addition, the plasmon modes of porous nanocage and nanoframe are red-shifted relative to the nanobox as the surface porosity of nanocage increases. In particular, the wavelengths at the peaks of these modes almost linearly depend on the surface porosity. Moreover, the scattering efficiency of the dipole mode is much higher than the absorption one. The former is broadband, while the latter narrowband. These modes are confirmed by their far-field scattering patterns, and the corresponding surface electric field distributions are also investigated. 相似文献
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8.
空心方形纳米结构能够激发更大面积的增强电场,故其可以作为衬底用于表面增强拉曼散射.应用离散偶极子近似算法研究了空心方形银纳米结构的消光光谱及其近场电场分布与入射光偏振方向之间的关系.研究表明,空心方形银纳米结构的表面等离子体共振峰不随入射光偏振方向的改变而移动,但是其表面增强电场分布却强烈地依赖于入射光的偏振方向.另外,还讨论了空心方形银纳米结构间的耦合作用对其表面等离子体共振模式的影响.结果发现,可以通过调节结构间的距离来改变结构间的耦合作用,同时改变了表面等离子体共振峰的位置.这些结果将为理解闭合纳米
关键词:
空心方形银纳米结构
表面等离子体
偏振
电场耦合 相似文献
9.
Jusserand B Vijayaraghavan MN Laruelle F Cavanna A Etienne B 《Physical review letters》2000,85(25):5400-5403
The contribution of elementary excitations in low-dimensional electron gases to resonant inelastic light scattering is found to be determined by interband transitions involving states at specific wave vectors. In modulation-doped GaAs/GaAlAs quantum wells, we detect only the single-particle excitations (SPE) at resonances with electron-hole transitions at the Fermi wave vector, and only plasmons at resonances with zone-center excitons. The plasmon cross section is comparable to the SPE when double electronic resonance is achieved by tuning the plasmon energy to a valence subband separation. 相似文献
10.
Changes in extinction spectra of nanostructured colloids of plasmon resonance particles are studied at different stages of their crystallization. The spontaneous crystallization is calculated by the method of Brownian dynamics, and the extinction spectra are calculated by the method of coupled dipoles. Based on the example of silver sols, we analyzed how separate parameters of the crystallizing disperse system affect the shape of the extinction contour in the plasmon absorption band. 相似文献
11.
Y. Fleger M. Rosenbluh Y. M. Strelniker D. J. Bergman A. N. Lagarkov 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(1):85-93
The extinction spectrum of a
dielectric film with periodic array of metallic
islands of different shapes and different
mutual distances
was studied both theoretically
and experimentally. It is shown, analytically,
numerically and experimentally, that the
positions of the surface plasmon resonances depend on
the nano-structural details.
We propose two ways of controlling plasmon resonance frequency:
changing the aspect ratio
of the elliptical (or rectangular) islands and changing their
mutual distances.
A new analytical asymptotic approach for calculating the optical
properties of such plasmonic systems is developed.
The results of our analytical and numerical studies are in
good qualitative agreement with experiment. 相似文献
12.
S. I. Pokutnii 《Physics of the Solid State》1997,39(4):528-531
It is shown in the dipole approximation that the cross section for resonance absorption and scattering of light by single-particle
local states of the charge carriers has different kinds of frequency and size dependence under different physical conditions.
Fiz. Tverd. Tela (St. Petersburg) 39, 606–609 (April 1997) 相似文献
13.
A. I. Parkhomenko A. M. Shalagin 《Journal of Experimental and Theoretical Physics》2008,106(5):858-868
The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation. 相似文献
14.
A. I. Parkhomenko A. M. Shalagin 《Journal of Experimental and Theoretical Physics》2005,100(2):283-293
The spectrum of weak probe field absorption (amplification) by two-level atoms experiencing collisions with buffer gas atoms in a strong resonance laser field is studied theoretically. Analysis is carried out for systems with a weak Doppler broadening under relatively mild constraints on the strong field intensity for the general case of an arbitrary change in the phase of the radiation-induced dipole moment in elastic collisions of gas particles. It is shown that, in spite of uniform broadening of the absorption line, the probe field spectrum exhibits a clearly manifested anisotropy to mutual orientation of the wavevectors of strong and probe radiation. It is found that the width of resonances in the probe field spectrum under definite conditions (that can easily be created in experiments) is proportional to the diffusion coefficient for atoms interacting with radiation. This fact can form the basis of the spectroscopic method for measuring the transport frequencies of collisions between particles absorbing radiation and buffer particles. It is shown that phase memory effects in collisions strongly modify the probe field spectrum both qualitatively and quantitatively. Simple operative formulas proposed for the probe field spectrum are convenient for experimental data processing. 相似文献
15.
Annealed Silver-Island Films for Applications in Metal-Enhanced Fluorescence: Interpretation in Terms of Radiating Plasmons 总被引:1,自引:0,他引:1
The effects of thermally annealed silver island films have been studied with regard to their potential applicability in applications
of metal-enhanced fluorescence, an emerging tool in nano-biotechnology. Silver island films were thermally annealed between
75 and 250∘C for several hours. As a function of both time and annealing temperature, the surface plasmon band at ≈420 nm both diminished
and was blue shifted. These changes in plasmon resonance have been characterized using both absorption measurements, as well
as topographically using Atomic Force Microscopy. Subsequently, the net changes in plasmon absorption are interpreted as the
silver island films becoming spherical and growing in height, as well as an increased spacing between the particles. Interestingly,
when the annealed surfaces are coated with a fluorescein-labeled protein, significant enhancements in fluorescence are osbserved,
scaling with annealing temperature and time. These observations strongly support our recent hypothesis that the extent of
metal-enhanced fluorescence is due to the ability of surface plasmons to radiate coupled fluorophore fluorescence. Given that
the extinction spectrum of the silvered films is comprised of both an absorption and scattering component, and that these
components are proportional to the diameter cubed and to the sixth power, respectively, then larger structures are expected
to have a greater scattering contribution to their extinction spectrum and, therefore, more efficiently radiate coupled fluorophore
emission. Subsequently, we have been able to correlate our increases in fluorescence emission with an increased particle size,
providing strong experiment evidence for our recently reported metal-enhanced fluorescence, facilitated by radiating plasmons
hypothesis. 相似文献
16.
金属纳米颗粒LSPR光纤生物传感DDA方法研究 总被引:1,自引:0,他引:1
研究了金属纳米颗粒的局部表面等离子体共振(LSPR)行为,并讨论了其在光纤生物传感领域的应用.采用离散偶极近似(DDA)的方法,从理论上分析了金属纳米颗粒的尺寸、形状对其传感灵敏度的影响.计算结果显示,金属纳米颗粒的等离子共振吸收峰同时受到颗粒尺寸和形状的影响,但形状对其传感灵敏度的影响最为明显,计算结果与实验数据能较好地吻合. 相似文献
17.
采用离散偶极子近似方法计算了内嵌圆饼空心方形银纳米结构的消光光谱以及其近场的电场强度分布,并进一步与空心方形纳米结构的消光光谱和表面电场做比较.结果表明,在耦合作用下内嵌圆饼空心方形银纳米结构不仅产生了新的共振模式,而且新的共振模式在传统表面增强拉曼散射的激发波长范围内,进而可以弥补由于实验上运用纳米切片法所制备的空心方形纳米结构尺寸较大导致其共振吸收峰在远红外波长范围的不足.此外,可以通过改变内嵌圆饼空心方形银纳米结构的形貌参数调节其表面等离子体共振峰的共振波长,以满足在表面增强拉曼散射、生物分子或化学分子探测上的应用. 相似文献
18.
银纳米棒光学性质的离散偶极近似计算 总被引:1,自引:0,他引:1
利用离散偶极近似 (Discretedipoleapproximation ,简称DDA)的方法 ,从理论上对粒子的形状、尺寸及周围介质等因素对银纳米粒子 ,特别是银纳米棒的光学性质的影响进行了较系统的研究 .计算表明 ,置于空气中的棒状银纳米粒子的光学性质与其形状密切相关 ,纵向表面等离子体共振吸收峰的位置随纳米棒长径比的增加呈现线性红移关系 .给出了空气中银纳米棒纵向表面等离子体共振吸收峰的位置随长径比变化的DDA拟合公式 .如果将金属纳米粒子置于折射率更高的介电环境中 ,其纵向等离子体共振吸收峰的位置进一步呈现线性红移关系 .合成的银纳米粒子的TEM图像及相关的UV VIS消光光谱显示DDA计算结果与实验值相当一致 .DDA算法与Mie′s理论在计算球状银纳米粒子的消光系数时给出很接近的结果 ,这表明用DDA的方法来分析银的光学性质是准确可靠的 ;而DDA算法对银纳米棒消光特性的成功拟合则表明 ,该算法相对Gans′理论而言 ,在研究纳米粒子的光学性质时具有更广的适用性及更高的准确性 . 相似文献
19.
The existence and nature of end and central plasmon resonances in a linear atomic chain, the 1D analog to surface and bulk plasmons in 2D metals, has been predicted by ab initio time-dependent density functional theory. Length dependence of the absorption spectra shows the emergence and development of collectivity of these resonances. It converges to a single resonance in the longitudinal mode, and two transverse resonances, which are localized at the ends and center of the atom chains. These collective modes bridge the gaps, in concept and scale, between the collective excitation of atomic physics and nanoplasmonics. It also outlines a route to atomic-scale engineering of collective excitations. 相似文献
20.
提出了一种同心椭圆柱-纳米管复合结构,该结构由金纳米管中内嵌椭圆形金柱构成,利用时域有限差分法分析了尺寸参数、周围环境及纳米管内核材料对该结构光学性质的影响.结果表明,调节椭圆柱芯的旋转角度可产生双重偶极-偶极Fano共振,其主要是由椭圆柱芯的纵向或横向偶极共振模式与纳米管的偶极成键和反成键模式杂化形成的超辐射成键模式和亚辐射成键模式之间的相互作用产生的,且共振特性可通过调节复合结构的尺寸参数控制,随椭圆柱长轴或短轴的增大而红移,随纳米管外径的增大或整体尺寸的减小而蓝移,当纳米管内径增大时高频Fano共振随着红移,而低频Fano共振先蓝移再红移,同时其对外界环境的变化不敏感,但对纳米管内核材料变化有着较好的响应.利用等离激元杂化理论对该现象进行了解释.这些结果可为构造其他类型的多波段Fano共振二维或三维纳米结构提供一种新的方式. 相似文献