共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Zhu Z. Sun J.-J. Li J.-W. Zhao 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):311-314
Under quasi-steady-state conditions, we investigated the photo-heat
conversion in a gold nanoshell by calculating the local equilibrium
temperature distribution. In a thinner gold shell, the hot spots take place
near the poles of both shell-surrounding and core-shell interface,
perpendicularly to the incident field. In a thicker gold shell, the hot
spots only take place near the core-shell interface. The maximum local
temperature also depends greatly on the core media and shell thickness.
Optimal heat generation can be obtained with small core dielectric constant
and thin shell thickness. The mechanism of this local heating distribution
is explained by the local field enhancement that is induced by the plasmon
coupling. 相似文献
2.
J. Ferber U.C. Fischer N. Hagedorn H. Fuchs 《Applied Physics A: Materials Science & Processing》1999,69(6):581-589
An internal reflection mode is introduced for scanning near-field optical microscopy (SNOM) with the tetrahedral tip. A beam
of light is coupled into the tip and the light specularly reflected out of the tip is detected as a photosignal for SNOM.
An auxiliary STM mode is used to control the distance during the scanning process and to record the topography of the sample
simultaneously with the SNOM image. Images were obtained of different metallic samples which show a contrast in the order
of 10% of the total reflected photosignal. In images of metallic samples an inverted contrast is consistently obtained compared
to images previously obtained of comparable samples in a transmission mode. The contrast shows a pronounced dependence on
the polarization of the incident beam with respect to the orientation of the edges of the tip. In the case of gold surfaces,
the photosignal as a function of distance between the tip and the surface shows a pronounced peak in the near-field range
of 0–20 nm which is tentatively attributed to the excitation of surface plasmons on the gold surface. The pronounced near-field
effects and the strong contrast in the near-field images and the resolution well below 50 nm are an indication of a highly
efficient coupling of the incident beam to a local excitation of the tip apex which is essential for the function of the tip
as a probe for SNOM.
Received: 17 May 1999 / Accepted: 18 May 1999 / Published online: 21 October 1999 相似文献
3.
P. Sarriugarte M. Schnell P. Alonso-González L. Arzubiaga F. Golmar F. Casanova L.E. Hueso R. Hillenbrand 《Optics Communications》2012,285(16):3378-3382
We study the propagation of mid-infrared surface plasmons on non-tapered and tapered two-wire transmission lines on Si and CaF2 substrates, the two materials representing substrates with large and small refractive index, respectively. A comparative numerical study predicts a larger effective wavelength and an increased propagation length (i.e. weaker damping) for the CaF2 substrate. By near-field microscopy we image the near-field distribution along the transmission lines and experimentally verify surface plasmon propagation. Amplitude- and phase-resolved near-field images of a non-tapered transmission line on CaF2 reveal a standing wave pattern caused by back-reflection of the surface plasmons at the open-ended transmission line. Calculated and experimental near-field images of tapered transmission lines on Si and CaF2 demonstrate that for both substrates the mid-IR surface plasmons are compressed when propagating along the taper. Importantly, the nanofocus at the taper apex yields a stronger local field enhancement for the low-refractive index substrate CaF2. We assign the more efficient nanofocusing on CaF2 to the weaker damping of the surface plasmons. 相似文献
4.
In this paper, the enhanced optical transmission through a special type of aperture of a bowtie shape is investigated through
near-field imaging and finite-difference numerical analysis. Under linear polarizations in two orthogonal directions, the
optical near fields of the bowtie aperture and comparable square and rectangular apertures made in gold and chromium thin
films are measured and compared. The bowtie aperture is able to provide a nanometer-sized optical spot when the incident light
is polarized across the bowtie gap and delivers a considerable amount of light. Localized surface plasmons are clearly observed
in the near-field images for both bowtie and rectangular apertures in gold, but invisible in chromium. Finite-difference time-domain
calculations reveal that, depending on the polarization of the incident light, the unique optical properties of the bowtie
aperture are a result of either the optical waveguide and the coupled surface plasmon polariton modes existing in the bowtie
gap or the coupling between the two open arms of the bowtie aperture.
PACS 81.07.-b; 07.79.Fc; 71.36.+c; 78.66.Bz; 42.79.Gn; 42.79.Vb 相似文献
5.
Shijie Liu Zicai Shen Weijing Kong Jian Shen Zhenxia Deng Yuanan Zhao Zhengxiu Fan 《Optics Communications》2006,267(1):50-57
Multi-layer dielectric (MLD) gratings for pulse compressors in high-energy laser systems should provide high diffraction efficiency as well as high laser induced damage thresholds (LIDT). Nonuniform optical near-field distribution is one of the important factors to limit their damage resistant capabilities. Electric field distributions in the gratings and multi-layer film region are analyzed by using Fourier modal method. Optimization of peak electric field in the gratings ridge is performed with a merit function, including both diffraction efficiency and electric field enhancement when the top layer material is HfO2 and SiO2, respectively. A set of optimized gratings parameters is obtained for each structure, which reduce the peak electric field within the gratings ridge to being respective 1.39 and 1.84 times the value of incident light respectively. Finally, we also discuss the effects of gratings refractive index, gratings sidewall angle and incident angle on peak electric field in the gratings ridge. 相似文献
6.
We investigated near-field optical (NFO) imaging characteristics of a small object placed on a dielectric slab by a computer-code using a three-dimensional volume integral equation with an effective iteration technique called the generalized minimal residual method. A simplified three-dimensional NFO microscope that consists of a small dielectric object placed on the dielectric substrate and a small dielectric sphere as a scanning probe-tip was considered. Calculating two-dimensional output images obtained from scattered far fields, we studied the effect of the substrate on NFO output images, the comparison of NFO output images with electrostatic field around the small object, the dependence of output image characteristics on the wavelength and the difference of imaging characteristics between incident plane waves and incident evanescent waves. 相似文献
7.
S. Grésillon R. Lecaque L. Williame J.C. Rivoal 《Applied physics. B, Lasers and optics》2006,84(1-2):167-173
Simultaneous topographical and near-field optical imaging have been performed on single gold particles of diameters close
to 12 nm. The optical source is a linearly polarized laser diode operating at λ=780 nm away from the plasmon resonance of
the particles. The experimental optical image is recorded with an apertureless scanning near-field optical microscope (ASNOM)
operating in transmission mode. It is compared to the components of the polarized scattered electric field around a single
cluster calculated using Mie formalism. We show that the tip used in the experiments is sensitive to the axial component of
the scattered field, thus allowing us to obtain the amplitude and the phase of the local field. Our derivation brings out
new information, usually shaded when applied to an ensemble of particles. In particular, the dipole model widely used to describe
the scattered field by a spherical particle is not suitable to describe the three components of the scattered field in the
near zone. Our results are of interest for fundamental studies of the optical properties of single metal clusters and the
control of local phenomena such as enhancement, extinction, etc.
PACS 07.79.Fc; 78.67.Bf; 78.35.+c 相似文献
8.
Ji-Young Kim Vladimir P. Drachev Hsiao-Kuan Yuan Reuben M. Bakker Vladimir M. Shalaev 《Applied physics. B, Lasers and optics》2008,93(1):189-198
Periodic arrays of paired and single gold nanorods were imaged in the near field using reflection and transmission modes of
a near-field scanning optical microscope at various wavelengths and polarizations of light in the visible range. The paired
nanorods act like nanoantenna, and an array of them was initially designed as a negative-index material for the near infrared.
Reverse contrast in reflection and transmission images is observed under illumination from the small aperture of a metal-coated
fiber probe. By changing the relative orientation of the rods to the polarization, the reverse contrast switches to the normal
contrast of near-field imaging. Coupling between the aperture and the nanorod array makes the contrast higher. Transmission
through the aperture is enhanced if the aperture probe is positioned between the nanorods. The average near-field transmission
exhibits an opposite sign of anisotropy relative to the far-field case. Aperture probes with larger diameters always show
normal imaging contrast. The results demonstrate that the broad angular spectra of small-aperture sources play a crucial role
in near-field interactions with nanorod arrays. The results also show that angular redistributions of these spectra after
transmission or reflection from the nanorod array are likely due to excitation of localized and propagating plasmons. 相似文献
9.
V. Lozovski Yu. Nazarok S. I. Bozhevolnyi 《Physica E: Low-dimensional Systems and Nanostructures》2001,11(4):2077
An exact analytical solution of the self-consistent equation for the local field is used to calculate the near-field optical images of pyramid-like nano-objects placed at a surface of a solid. The diagram method developed previously for near-field image formation is generalized in order to describe layered objects, which are treated as many-body systems. The near-field optical images of triangular and square pyramids are calculated for the illumination configuration as well as those of triangular and square prisms. It is found that the near-field images of nanoparticles having the dielectric constant close to that of the substrate change rapidly and in a complicated manner with the probe–sample distance. 相似文献
10.
It is shown that the polarization states of optical spots at the nanoscale can be manipulated to various points on the Poincaré
sphere using a plasmonic nanoantenna. Linearly, circularly, and elliptically polarized near-field optical spots at the nanoscale
are achieved with various polarization states on the Poincaré sphere using a plasmonic nanoantenna. A novel plasmonic nanoantenna
is illuminated with diffraction-limited linearly polarized light. It is demonstrated that the plasmonic resonances of perpendicular
and longitudinal components of the nanoantenna and the angle of incident polarization can be tuned to obtain optical spots
beyond the diffraction limit with a desired polarization and handedness. 相似文献
11.
T. Brixner F.J. García de Abajo C. Spindler W. Pfeiffer 《Applied physics. B, Lasers and optics》2006,84(1-2):89-95
We theoretically demonstrate the control of electromagnetic field properties on a sub-diffraction length scale, by polarization
shaping of tightly focused femtosecond laser pulses. The field distribution in a tight focus is represented as a superposition
of plane waves. The near-field of a model nanostructure is then obtained as a sum of the near-field distributions induced
by the planar waves components. A self-consistent solution of Maxwell’s equations in the frequency domain yields the near-field
distributions for planar wave illumination. Adaptive optimization of the incident polarization pulse shape using an evolutionary
algorithm allows controlling of a number of observables, such as local nonlinear flux, simultaneous spatial and temporal control
of the intensity evolution, and control of the local spectrum. The tight focusing reduces the controllability of the flux
distribution in comparison to plane wave illumination. However, it is still possible to control the spatial and temporal field
evolution for particular locations in the vicinity of the nanostructure.
PACS 42.65.Re; 78.47.+p; 78.67.-n; 82.53.-k 相似文献
12.
Multipolar plasmon optical excitations at spherical gold nanoparticles and their manifestations in the particle images formatted
in the particle surface proximity are studied. The multipolar plasmon size characteristic: plasmon resonance frequencies and
plasmon damping rates were obtained within rigorous size dependent modelling. The realistic, frequency dependent dielectric
function of a metal was used. The distribution of light intensity and of electric field radial component at the flat square
scanning plane scattered by a gold sphere of radius 95 nm was acquired. The images resulted from the spatial distribution
of the full mean Poynting vector including near-field radial components of the scattered electromagnetic field. Monochromatic
images at frequencies close to and equal to the plasmon dipole and quadrupole resonance frequencies are discussed. The changes
in images and radial components of the scattered electromagnetic field distribution at the scanning plane moved away from
the particle surface from near-field to far-field region are discussed. 相似文献
13.
I. L. Garzón M. R. Beltrán G. González I. Guterrez-González K. Michaelian J. A. Reyes-Nava J. I. Rodrguez-Hernández 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):105-109
Theoretical and experimental information on the shape and
morphology of bare and passivated gold clusters is fundamental
to predict and understand their electronic, optical, and other
physical and chemical properties. An effective theoretical
approach to determine the lowest-energy configuration (global
minimum) and the structures of low energy isomers (local minima)
of clusters is to combine genetic algorithms and many-body
potentials (to perform global structural optimizations), and
first-principles density functional theory (to confirm the
stability and energy ordering of the local minima). The main
trend emerging from structural optimizations of bare Au clusters
in the size range of 12-212 atoms indicates that many
topologically interesting low-symmetry, disordered structures
exist with energy near or below the lowest-energy ordered
isomer. For example, chiral structures have been obtained as the
lowest-energy isomers of bare Au28 and
Au55 clusters, whereas in the size-range
of 75-212 atoms, defective Marks decahedral structures are
nearly degenerate in energy with the ordered symmetrical
isomers. For methylthiol-passivated gold nanoclusters
[Au28(SCH3)16
and
Au38(SCH3)24],
density functional structural relaxations have shown that the
ligands are not only playing the role of passivating molecules,
but their effect is strong enough to distort the metal cluster
structure. In this work, a theoretical approach to characterize
and quantify chirality in clusters, based on the Hausdorff
chirality measure, is described. After calculating the index of
chirality in bare and passivated gold clusters, it is found that
the thiol monolayer induces or increases the degree of chirality
of the metallic core. We also report simulated high-resolution
transmission electron microscopy (HRTEM) images which show that
defects in decahedral gold nanoclusters, with size between 1-2
nm, can be detected using currently available experimental HRTEM
techniques. 相似文献
14.
研究光在微纳结构中的分布与传播, 实现在纳米范围内操纵光子, 对于微型光学芯片的设计有着重要意义. 本文利用聚焦离子束刻蚀方法, 在基底为石英玻璃的150 nm厚金膜上刻制了不同参数的阿基米德螺旋微纳狭缝结构, 通过改变入射光波长、手性、及螺旋结构手性和螺距等方式, 在理论和实验上系统地研究了阿基米德螺旋微纳结构中的表面等离激元聚焦性质. 我们发现, 除了入射激光偏振态、螺旋结构手性之外, 结构螺距与表面等离激元波长的比值也可以用来控制结构表面电场分布, 进而在结构中心形成0阶、1阶乃至更高阶符合隐失贝塞尔函数的涡旋电场. 通过相位分析, 我们对涡旋电场的成因进行了解释. 并利用有限时域差分的模拟方法计算了不同螺距时, 结构中形成的电场及相应空间相位分布. 最后利用扫描近场光学显微镜, 观测结构中不同的光场分布, 在结构中心得到了亚波长的聚焦光斑及符合不同阶贝塞尔函数的涡旋形表面等离激元聚焦环. 相似文献
15.
Resonantly enhanced transmission of light through subwavelength apertures with dielectric filling 总被引:1,自引:0,他引:1
Huizhong Xu 《Optics Communications》2009,282(7):1467-4809
Using both analytical and numerical methods to study transmission of light through dielectric-filled subwavelength apertures in a real metal, we have found that a propagating mode can in principle exist inside a waveguide of arbitrary small size if a particular relationship between the dielectric constants of the cladding and filling materials at the incident frequency is satisfied. Practical transmission through a subwavelength aperture of finite depth can be enhanced when the depth is such that Fabry-Pérot-like resonances are excited. For 810 nm light incident on a silicon-filled 50-nm-diameter aperture in a 200-nm-thick gold film, we found that a normalized near-field intensity ratio of 1.6 at the exit can be achieved. This resonantly enhanced transmission phenomenon may be advantageously applicable to near-field scanning optical microscopy and single-molecule spectroscopy. 相似文献
16.
T. Miyanishi T. Sakai N. N. Nedyalkov M. Obara 《Applied Physics A: Materials Science & Processing》2009,96(4):843-850
Nanohole fabrication process with gold nanoparticles irradiated by femtosecond laser at different incident angles is investigated.
Nanoparticles with diameter of 200 nm and laser irradiation with center wavelength of 800 nm are used in the present study.
The analysis of the electromagnetic field distribution in the near-field zone of the particle is made by simulations based
on finite-differential time domain (FDTD) method. It is shown that when gold nanoparticle is irradiated by laser pulse surface
plasmon excitation can be induced, and associated with it, high-intensity near field is produced in a limited area around
the particle. It is found that the change of the irradiation conditions by means of irradiation from various incident directions
gives a possibility of laser nanoprocessing with tunable characteristics. Our results show that enhanced optical intensity
is able to be induced on the substrate surface regardless of incident direction of the laser due to the image charge interaction with the substrate. Furthermore, the use of p-polarized
laser irradiation at a certain angle gives a minimum of the spatial dimensions of the enhanced zone on the substrate which
is about two times smaller than that obtained at normal incidence. 相似文献
17.
J.-Y. Chu T.-J. Wang J.-T. Yeh M.-W. Lin Y.-C. Chang J.-K. Wang 《Applied Physics A: Materials Science & Processing》2007,89(2):387-390
We report a near-field study of the excitation and propagation of surface plasmon on ordered Ag elliptical hole arrays with
a scattering-type scanning near-field optical microscope. Strong dipole-like local plasmon is identified at each individual
hole from near-field optical intensity and phase images. The excitation of the local plasmon at the elliptical hole is found
to follow polarization excitation constraint. The coherent superposition of these local plasmon waves to form an extended
surface plasmon wave propagating to an adjacent hole array is observed directly. The near-field results are consistent with
the results obtained from far-field extraordinary transmission measurements.
PACS 42.25.Bs; 42.25.Hz; 42.25.Ja; 42.25.Kb; 07.79.Fc 相似文献
18.
采用相对论有效原子实势(RECP)近似和密度泛函(B3LYP)方法,选择LANL2DZ基组,优化得到了AunY(n=1—9)二元掺杂团簇稳定的基态结构和电子性质.研究结果表明,掺杂Y原子的AunY(n=1—9)团簇随n的变化,其电离势、电子亲合能和费米能级与Aun(n=2—9)一样具有“奇-偶”振荡效应;团簇离子的稳定性具有“幻数”现象,Au2Y+和Au6Y+比其他团簇离子更稳定,与质谱实验结果一致;同一团簇中,团簇最稳定的异构体(基态)是趋于Y原子有最大的邻近的Au原子数.
关键词:
Au-Y团簇
密度泛函
平衡几何结构
电子性质 相似文献
19.
Go Obara Yuto Tanaka Tomoya Miyanishi Minoru Obara 《Applied Physics A: Materials Science & Processing》2011,102(3):551-557
We present localized optical field distribution properties in the vicinity of gold particles on a silicon substrate by backward
and forward irradiation. It is technically difficult to fabricate nanostructures on the surface by a conventional forward
laser incident to the substrate because gold nanoparticles easily aggregate to form double-layered particle arrays. We calculated
enhanced optical field properties in order to pattern the substrate surface only with a template of the bottom-layered particle
arrays in the case that the backward irradiation of a femtosecond laser is used in the system of aggregated double-layered
gold nanoparticle arrays. With the backward irradiation, the optical field intensity in the substrate for the double-layered
hexagonal arrays is found to be only 30% lower than the mono-layered system. Moreover, a near field cannot be generated with
the forward irradiation. As a result, only the backward irradiation scheme is found to be effective for uniform surface nanopatterning
at enhanced plasmonic near-field zones. 相似文献
20.
The surface plasmon enhanced ultra-low threshold second harmonic generation is observed, designed and simulated in whispering gallery resonator made of MgO doped periodically poled LiNbO3. Here the electric field associated with incident optical radiation of picowatt level is amplified to milliwatt level through surface plasmon resonance in Kretschmann geometry which is formed by a BK7 prism plane, 29 nm thin gold layer and 20 nm thin GaAs layer. This enhanced electric field then coupled to a whispering gallery resonator, which facilitated the generation of second harmonic for an incident laser radiation of picowatt level. In this proposed configuration with an incident optical power of 94.6 pW, generated second harmonic through whispering gallery resonator is found to be 14.6 mW. 相似文献