Surface plasmon polariton scattering by small ellipsoid particles

Scattering of surface plasmon polaritons (SPP’s) by small ellipsoid particles placed near a dielectric–metal interface is theoretically considered. Using the Green’s function formalism and the dipole approximation, we consider the differential and total scattering cross-sections associated with the SPP-to-SPP scattering as well as with the SPP scattering into waves propagating away from the interface, analyzing the influence of system parameters. As an example, scattering cross-sections of differently shaped gold spheroid particles placed near an air–gold interface are evaluated at the light wavelength of 800 nm. It is shown that the differential and total cross-sections depend strongly upon the particle-to-surface distance, the ratio between the major and minor axes and their orientation with respect to both the interface and the direction of SPP incidence. Implications of the obtained results to the design of SPP micro-optical components are also discussed.     

Pulsed microwave-driven argon plasma jet with distinctive plume patterns resonantly excited by surface plasmon polaritons

Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air.The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes.The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons.Moreover,for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave,the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas,frequencies of pulsed modulator,duty cycles of pulsed microwave,peak values of input microwave power,and even by using different materials of dielectric tubes.In addition,the emission spectrum,the plume temperature,and other plasma parameters are measured,which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.     

Effective-medium approach for surface-localized magnetic polaritons in magnetic (ferromagnetic and antiferromagnetic) superlattices

The general effective-medium dispersion relations are derived for surface-localized magnetic polaritons which propagate parallel to the surface between a superlattice and semi-infinite bulk material, as applied to ferromagnetic and antiferromagnetic superlattices, in the situation when a static magnetic field is applied in the plane of the layers and parallel to the magnetization. The dependence of the energy of the surface waves on the volume fraction of the ferromagnetic superlattice component and the influence of the external magnetic field on the spectrum of the surface magnetic polaritons for the antiferromagnetic superlattice are investigated. The spectrum of the surface-localized magnetic polaritons which appear at the junction of the magnetic (ferromagnetic and antiferromagnetic) superlattice with the magnetic material are more complex, in contrast to the cases of semi-infinite magnetic material or semi-infinite magnetic SL. It is essential that in all cases in the presence of the external magnetic field the spectrum of the magnetic polaritons are non-reciprocal. The properties of surface polaritons are discussed in detail for the system ferromagnetic superlattice (YIG/non magnet)/YAG and the antiferromagnetic superlattice (MnF₂/ZnF₂)/FeF₂.     

ZnO based planar and micropillar resonators

In this paper we report on planar and microscopic cylindrical resonators with ZnO as the cavity and active medium surrounded with ZrO₂/MgO Bragg reflectors. We have observed resonator behaviour of these structures and, for the planar resonators, exciton–polariton coupling with a mode splitting of about 50 meV.     

基于表面等等离波子的新型Y分支波导

新型高效的纳米光波导器件的研制纳米集成光学的核心技术之一。Y分支波导作为最基本的分光和光路连接元件是纳米光学器件设计与制备的基础。运用时域有限差分(FDTD)法,模拟计算了基于表面等等离波子(SPP)的纳米Y分支波导的传输特性。结果表明,该新型Y分支波导在光通信波段可以实现大角度的分光功能,且在180°分支情况下,传输效率仍高达92.8%以上。另外,该波导还具有导波性能良好、对分叉处间隙缺陷大小不敏感及制作容差较大和器件尺寸在纳米量级等特点。对该新型光波导器件的研究为未来纳米集成光学器件的研制和应用有一定的指导意义。     

Rainbow trapping based on long-range plasmonic Bragg gratings at telecom frequencies

The group velocity of long-range surface plasmon polaritons (LRSPPs) in a wide frequency bandwidth at infrared frequencies is significantly reduced by dielectric gratings of graded thickness on both sides of a thin metal film. This structure can reduce the propagation loss of slow surface plasmons in "rainbow trapping" systems based on plasmonic Bragg gratings. Compared with dielectric gratings of graded thickness on a single side of a metal film, the proposed structure is able to guide slow light with a much longer propagation distance for the same group index factor. Finite- difference time-domain simulation results show that slow LRSPPs with the group velocity of c/14.5 and the propagation distance of 10.4 μm are achieved in dielectric gratings of uniform thickness on both sides of a thin metal film at 1.62 μm.     

Spatial condensation of trapped polaritons in graphene and semiconductor structures

The theoretical and experimental status of the Bose–Einstein Condensation (BEC) of trapped quantum well (QW) polaritons in a microcavity is presented. The results of recent experiments that have shown the possibility to create an in-plane harmonic potential trap for a two-dimensional (2D) exciton polaritons in a cavity are discussed. We report the theory of BEC and of the trapped QW exciton polaritons in a microcavity. In addition, we study the BEC of trapped magnetoexciton polaritons in a graphene layer (GL) embedded in an optical microcavity in high magnetic field. In both cases the polaritons are considered to be in a harmonic potential trap. We compare the theoretical results with the existing experiments and discuss the experimental observation of predicted phenomena.     

Effects of the piezoelectric field on the modulation of exciton–polaritons by surface acoustic waves

Surface acoustic waves (SAWs) provide a powerful tool for the modulation of polaritons in GaAs-based microcavities. In this contribution, we compare the modulation introduced by SAWs propagating along piezoelectric and non-piezoelectric crystal directions of the sample surface. Strain calculations reveal that the type-I band-gap modulation induced by the strain field is comparable for both SAW types. Piezoelectric SAWs have, however, an intrinsic longitudinal electric field, which can dissociate quantum well (QW) excitons and, thus, degrade the modulation. Images of the polariton far-field photoluminescence reveal this behavior for different excitation conditions.     

一维金属光栅的光学反射吸收

利用RCWA(rigid coupled-wave analysis)方法研究了一维金属光栅的反射特性,考察了 瑞利反常、表面等离激元驻波共振和几何共振三种共振吸收机理,分析了这三种机理的相互作用,如表面等离激元驻波共振和几何共振可以形成混合模式. 在反射式复合金属光栅中,确认了第四种共振形式,即相位共振. 数值计算表明相位共振对光学吸收的影响有两种形式: 当光栅周期大于一个波长时,相位共振导致尖锐的吸收峰,峰位在几何共振吸收峰一侧;当光栅周期小于一个波长时,相位共振导致混合模式的共振吸收峰发生劈裂. 对一维金属光栅反射特性的研究增加了对金属光栅共振吸收模式及其相互作用的认识. 关键词： 一维金属光栅 瑞利反常 表面等离激元 相位共振     

干涉高斯光诱导的表面等离子激元驻波场的分析

考虑到实际入射光强的空间分布不均匀,基于Kretschmann模型并采用角谱方法分析模拟了两束高斯光干涉诱导表面等离子激元(SPP)驻波场。与理想平面波不同,高斯光诱导的SPP干涉条纹幅值大小不等,分布复杂,这表明光强空间非均匀程度会严重地影响到曝光深度的分布。还分析了金属薄膜的厚度、损耗以及光刻胶的介电常数对SPP驻波场的影响,并得出不恰当的金属板厚和细微损耗都会极大削弱SPP驻波场,而如果光刻胶的介电常数过大则有可能产生不了表面等离子体共振的结论。