半导体增益介质对MSM 等离子体波导的传输损耗补偿研究

为了深入地研究在紫外波长范围内利用增益介质补偿等离子传输损耗,设计了具有半导体增益介质的金属-半导体-金属（Metal-Semiconductor-Metal,MSM）等离子体光波导结构。基于时域有限差分法（FDTD）,对该波导结构的传输损耗、有效折射率随几何结构的依赖关系进行了分析。进一步研究了利用II-VI 族半导体ZnO 作为增益介质时的无损传播条件。结果表明,当ZnO 宽度为80 nm 时,MSM 等离子波导可以实现紫外波长范围的无损传播;当ZnO 宽度大于80 nm 时,传播增益明显大于损耗,可以实现等离子极化波的传播放大,为表面等离子体基元纳米激光器技术提供理论依据。     

银纳米线表面等离子体波导的传输损耗特性研究

通过远场聚焦光斑激发银纳米线表面等离子体激元(SPP: Surface Plasmon Polariton),并搭建银纳米线路由传输结构改变SPP的传输距离,研究了SPP的传输损耗特性。实验上测量了置于玻璃衬底表面的银纳米线在不同激发波长时SPP的传输损耗系数,发现SPP的传输损耗具有波长依赖性：632.8nm激光激发时,传输损耗系数为0.115 ,780nm激光激发时,传输损耗系数为0.0923 ,即传输损耗系数在长波激发时小,而在短波激发时大。测量结果对基于银纳米线波导的集成微纳光学系统设计有很好的指导作用。     

248 nm imaging photolithography assisted by surface plasmon polariton interference

A new photolithography technique for 248 nm based on the interference of surface plasmon waves is proposed and demonstrated by using computer simulations.The basic structure consists of surface plasmon polariton（SPP）interference mask and multi-layer film superlens.Using the amplification effect of superlens on evanescent wave,the near field SPP interference pattern is imaged to the far field,and then is exposed on photo resist（PR）.The simulation results based on finite difference time domain（FDTD）method show that the full width at half maximum（FWHM）of the interference pattern is about 19 nm when the p-polarization light from 248 nm source is vertically incident to the structure.Meanwhile,the focal depth is 150 nm for negative PR and 60 nm for positive PR,which is much greater than that in usual SPP photolithography.     

Manipulable and Hybridized,Ultralow‐Threshold Lasing in a Plasmonic Laser Using Elliptical InGaN/GaN Nanorods

Manipulating stimulated‐emission light in nanophotonic devices on scales smaller than their emission wavelengths to meet the requirements for optoelectronic integrations is a challenging but important step. Surface plasmon polaritons (SPPs) are one of the most promising candidates for sub‐wavelength optical confinement. In this study, based on the principle of surface plasmon amplification by the stimulated emission of radiation (SPASER), III‐Nitride‐based plasmonic nanolaser with hybrid metal–oxide–semiconductor (MOS) structures is designed. Using geometrically elliptical nanostructures fabricated by nanoimprint lithography, elliptical nanolasers able to demonstrate single‐mode and multimode lasing with an optical pumping power density as low as 0.3 kW cm^?2 at room temperature and a quality Q factor of up to 123 at a wavelength of ≈490 nm are achieved. The ultralow lasing threshold is attributed to the SPP‐coupling‐induced strong electric‐field‐confinement in the elliptical MOS structures. In accordance with the theoretical and experimental results, the size and shape of the nanorod are the keys for manipulating hybridization of the plasmonic and photonic lasing modes in the SPASER. This finding provides innovative insight that will contribute to realizing a new generation of optoelectronic and information devices.     

Recent advancements in surface plasmon polaritons-plasmonics in subwavelength structures in microwave and terahertz regimes

This paper presents a review of recent investigational studies on exciting Surface Plasmon Polaritons (SPPs) in MicroWave (MW) and TeraHertZ (THz) regimes by using subwavelength corrugated patterns on conductive or metal surfaces. This article also describes SPP Microstrip (MS) structures at microwave and terahertz frequencies, and compares their significance with that of conventional MS Transmission Lines (TL), in order to tackle the key challenges of high gain, bandwidth size, compactness, TL losses, and signal integrity in high-end electronic devices. Because they have subwavelength properties, surface plasmon polaritons are gaining attention for their improved performance and ability for miniaturization in high-speed dense circuits. They possess comparably minuscule wavelength compared to incident light (photons). Consequently, they can demonstrate stronger spatial confinement and higher local field intensity at optical frequencies. In addition to engineering spoof SPP waveguides, which are created by engraving grooves and slits on metal surfaces to allow operation on at low frequencies (microwave and terahertz), semiconductors with smaller permittivity values and thus lower free charge carrier concentration have been demonstrated as a potential candidate in plasmonic devices. If necessary, further tuning of semiconductor-based SPP structures is aided by controlling the charge carrier concentration through doping, or by external stimuli such as optical illumination or thermal excitation of charge carriers from valence to conduction bands. This article conclusively covers previously elucidated perspectives on manipulating SSPPs in the MW and THz ranges, and emphasizes how these could steer next-generation plasmonic devices.     

Thermosensitive Plasmonic Color Enabled by Sodium Metasurface

Active plasmonic nanostructures have attracted tremendous interest in nanophotonics and metamaterials owing to the dynamically switchable capabilities of plasmonic resonances. In this study, tunable hybrid plasmon resonances (HPR) of sodium metasurfaces through heat-initiated structural transformation is experimentally demonstrated. A HPR is formed by coupling surface plasmon polaritons (SPP) and gap plasmon resonances (GPR), whose resonant wavelengths are highly sensitive to gaseous nanogaps. By carefully manipulating the thermo-assisted spin-coating process and post-thermal treatment, tuning of the HPR is achieved because of the phase transition between the antidome and nanodome structural profiles of liquid sodium inside the patterned fused silica substrates. Furthermore, the figure of merit of the heat initiated variable structure-spectrum is demonstrated that is highly dependent on the size of the substrate patterns, based on which temperature-sensitive plasmonic color and “invisible ink” of sodium metasurfaces are demonstrated. These findings can lead to new solutions for manipulating low-cost and high-performance active plasmonic devices.     

MDM光波导激发高阶SPP模的传输特性

研究了金属-介质-金属(MDM)型表面等离子体激元(SPP)光波导的电磁特性。理论计算结果表明,对于633nm的TM偏振入射光,当介质膜层厚度小于85nm时,波导中只能激发产生一阶SPP模(基模),其余高阶模全部截止。随着介质膜厚度增加,高阶SPP模逐渐被激发产生。当介质膜层厚度较小时,SPP模的有效折射率的实部随阶数的增加而减小,而虚部则随阶数的增加而增加,SPP基模具有最大传输距离。然而,当MDM波导中的介质层厚度超过0.555μm时,由于三阶SPP模的电磁场主要集中在离金属层相对较远的介质层中,其有效折射率的虚部具有最小值,具有最大的传输距离,而非基模。当入射光波长为633nm介质层厚度为0.9μm时,Ag/SiO2/Ag光波导中三阶SPP模的传输距离达到约150μm。     

MIM 结构中腔的物理性质对SPP传播的分析

为了研究MIM 结构中腔的物理性质对SPP 传播的影响,采用了对波导模式、谐振和反射系数以及相位分析的理论方法,讨论了腔长和厚度对SPP 传播的相关参数的影响,仿真了MIM 波导中电动势、腔长和反射系数等参数在结构中作用.结果表明,SPP 传播产生的电动势能达到相对较大的1V,激发产生的能场会有放大的作用;腔的有效功率变化与腔长变化一致,不同的腔厚度中腔长对SPP 传播的结果趋势相同;近场中传播系数存在一个最大值.这一问题的分析与讨论对非线性THz光谱研究、纳米级光电探测、SPP 模式的发生器、强局域场都具有一定的意义.     

Photocontrollable Chiral Switching and Selection in Self‐Assembled Plasmonic Nanostructure

Reversible photocontrol of dynamic chirality in self‐assembly systems is of great importance in exploitations of artificial nanomachines for scientific and industrious applications. Here, a new strategy is proposed for achieving optically chiral controls based on photoswitchable plasmonic nanostructures. Chiral plasmonic nanoassemblies that are responsive to optomechanical perturbations exerted by circular polarized light (CPL) in the visible (vis)/near infrared (NIR) region are designed. The reversible photoswitching between opposite chiral states is verified by circular dichroism (CD) spectral signals. Theoretical simulations reveal the key role of optical torques in driving this chiral switching. By regulating light polarization or tuning light frequency to excite different plasmonic modes of the nanostructures, such an optomechanically driven chiral switching can enable a directed mirror‐symmetry breaking and selective chiral amplification in nanoassemblies. This plasmon‐based photoswitching nanosystem can operate at the optical transparent window, showing particular advantages over most of the molecular photoswitches for applications in living systems.     

Finite Element Analysis of Lossless Propagation in Surface Plasmon Polariton Waveguides With Nanoscale Spot-Sizes

We present simulation results on the propagation characteristics of active plasmonic waveguides at 1.55 mum wavelength based on semiconductors as the active gain media. Three waveguide structures were investigated: metal rib, metal-semiconductor-metal (MSM), and triangular metal groove. In all three structures, we observed strong plasmon mode confinement with nanoscale spot-sizes and corresponding simulated gain values compatible with existing semiconductor technology. We show the effect of systematic modification of waveguide geometry on the required gain for achieving lossless propagation in all the three plasmonic waveguide structures. We demonstrate that lossless propagation with subwavelength spot sizes well below the diffraction limit of light can be obtained by controlling the geometrical parameters of the proposed waveguides.     

Heavily doped silicon:A potential replacement of conventional plasmonic metals

The plasmonic property of heavily doped p-type silicon is studied here.Although most of the plasmonic devices use metal-insulator-metal(MIM)waveguide in order to support the propagation of surface plasmon polaritons(SPPs),metals that possess a number of challenges in loss management,polarization response,nanofabrication etc.On the other hand,heavily doped p-type silicon shows similar plasmonic properties like metals and also enables us to overcome the challenges pos-sessed by metals.For numerical simulation,heavily doped p-silicon is mathematically modeled and the theoretically obtained re-lative permittivity is compared with the experimental value.A waveguide is formed with the p-silicon-air interface instead of the metal-air interface.Formation and propagation of SPPs similar to MIM waveguides are observed.     

Influence of Mode Loss on the Feasibility of Grating-Assisted Optical Fiber Surface Plasmon Resonance Refractive Index Sensors

In this paper, the influence of mode loss on the feasibility of grating-assisted optical fiber surface plasmon resonance (SPR) refractive index (RI) sensors is investigated. The loss of surface plasmon polarition (SPP) mode plays a key role in the design and implementation of such sensors. It is demonstrated through simulation that the grating length should be smaller than or comparable with the propagation length of SPP mode in order to achieve effective coupling. The loss of SPP mode is the severe limiting factor for the implementation of the grating-assisted SPR-RI sensors. More generally, in order to achieve effective mode coupling with the help of waveguide grating, the grating length is bounded by the shortest propagation length of the modes in lossy waveguides.     

High System Performance with Plasmonic Waveguides and Functional Devices

Photonics offers a solution to data communication between logic devices in computing systems; however, the integration of photonic components into electronic chips is rather limited due to their size incompatibility. Dimensions of photonic components are therefore being forced to be scaled down dramatically to achieve a much higher system performance. To integrate these nano‐photonic components, surface plasmon‐polaritons and/or energy transfer mechanisms are used to form plasmonic chips. In this paper, the operating principle of plasmonic waveguide devices is reviewed within the mid‐infrared spectral region at the 2 µm to 5 µm range, including lossless signal propagation by introducing gain. Experimental results demonstrate that these plasmonic devices, of sizes approximately half of the operating free‐space wavelengths, require less gain to achieve lossless propagation. Through optimization of device performance by means of methods such as the use of new plasmonic waveguide materials that exhibit a much lower minimal loss value, these plasmonic devices can significantly impact electronic systems used in data communications, signal processing, and sensors industries.     

基于SPP的1550纳米光波导的超长传输特性

采用严格电磁理论研究了介质-金属-介质型光波导激发表面等离子激元(SPPs)的电磁特性,对比分析了SPP波在SiO2/Ag/SiO2和Si/Ag/Si光波导的传输距离。研究表明,对于1550nm光通信波长入射光及10nm厚的金属银膜层,SiO2/Ag/SiO2光波导中非对称SPP的传输距离可达40cm,明显高于对称SPP波的传输距离,也显著高于非对称SPP波在Si/Ag/Si波导中的传输距离,具有超长传输距离;随着金属层厚度的增加SPP波的传输距离明显减小,当银层厚度超过50nm后,非对称的SPP在SiO2/Ag/SiO2及Si/Ag/Si波导中的传输距离趋于一致,约为200nm;此时银层厚度变化对SPP波传输距离的影响明显减弱。     

AMM cladding fiber for coupled plasmonic propagation and core guidance

Dual effect of surface plasmon propagation and classical core guidance is made possible in this work with the integration of metamaterial in a fiber. Here, the alternate layers of \(\hbox {TiO}_{2}\) and Ag form anisotropic metamaterial that helps in plasmonic propagation. The designed fiber with the proposed metamaterial as a cladding supports both normal core guidance and surface guidance at different wavelength based on their anisotropy. Parameters such as dispersion and confinement loss are analyzed at different wavelength. Simulation results are obtained to confirm the proper propagation of modes.     

任意拓扑荷光学旋涡的产生及应用

光学旋涡在很多领域开展了广泛的研究和应用。介绍了一种基于涡旋波片的光学旋涡产出方法,并通过波片组合的方法可以产生任意拓扑荷的光学旋涡,该方法具有很好的灵活性。同时由于波片的透过率非常高,实验中拓扑荷为3 的光学旋涡的产生效率高达93%以上。通过干涉产生的叉形光栅叉数和方向进一步检测了产生光学旋涡的拓扑荷。利用产生的光学旋涡还进行了初步的光学操控实验,验证了轨道角动量对于微颗粒的动态操控作用。该方法将在更多领域得到推广和应用。     

形状双折射金属表面等离激元的特征长度

针对p偏振,研究形状双折射金属和常规介电材料界面的表面等离激元(SPP)。基于形状双折射金属介电常数的双轴各向异性和SPP的色散关系,分别在X方向和Y方向讨论SPP波长、传播距离以及在两种介质中的穿透深度等特征长度的变化规律。另外,分别讨论形状双折射金属的3个结构参数对SPP特征长度的影响,发现X方向的结构周期变化只影响Y方向的SPP特征长度,Y方向的结构周期变化只影响X方向的SPP特征长度,纳米孔半径的变化同时影响X方向和Y方向的SPP特征长度。     

Parametric amplification in spatially extended media and application to the design of tuneable oscillators at optical frequencies

A theory of travelling- and backward-wave variable parameter amplification appropriate to the amplification of a light beam is developed. It is an extension of the theory of Tien and Suhl for one-dimensional propagation to the case in which the pump wave, signal wave and idler waves have different directions of propagation. The theory is then applied to the design of a tuneable oscillator at optical wavelengths. The device is tuned by changing the orientation of a parallel mirror system. It appears that currently available pulsed laser powers are sufficient to drive such devices and that a continuous tuning range over a three to one interval in frequency is possible.     

An Electromagnetic Crystal Green Function Multiple Scattering Technique for Arbitrary Polarizations, Lattices, and Defects

A generalized electromagnetic crystal (EC) Green function (GF) multiple scattering technique (MST) that permits the simulation of transverse electric and magnetic waves in 2-D EC devices created by replacing crystal cylinders by nonconforming ones is presented. The EC may be defined on a square or triangular lattice. Both EC and nonconforming cylinders can be of arbitrary shape and composition. Integral equations in terms of equivalent currents residing on circular surfaces centered about the nonconforming cylinders are constructed using GFs innate to the background EC. Contrary to the (conventional) free-space GF MST, the proposed generalized EC GF MST yields sparse systems of equations that can be solved efficiently by multifrontal methods. A combination of the generalized EC GF MST with a volume integral-equation- and/or finite-element-based scheme to calculate scattering matrices of noncircular/inhomogeneous/plasmonic cylinders yields a very powerful tool that permits simulating wave propagation in a very broad class of EC devices. The generalized EC GF MST is applied to the analysis of a wide variety of practical EC devices, including a third-order Chebyshev bandpass filter, a pair of power dividers, two channel drop filters, a large multiplexer-demultiplexer, a set of bended waveguides, and waveguide filters comprising noncircular or plasmonic cylinders     

On the interplay of cell thickness and optimum period of silicon thin‐film solar cells: light trapping and plasmonic losses

Light trapping and photon management in honeycomb‐textured microcrystalline silicon solar cells are investigated experimentally and by modeling of the manufacturing process and the optical wave propagation. The solar cells on honeycomb‐textured substrates exhibit short circuit current densities exceeding 30 mA/cm² and energy conversion efficiencies of up to 11.0%. By controlling the fabrication process, the period and height of the honeycomb‐textured substrates are varied. The influence of the honeycomb substrate morphology on the interfaces of the individual solar cell layers and the quantum efficiency is determined. The optical wave propagation is calculated using 3D finite difference time domain simulations. A very good agreement between the optical simulation and experimental results is obtained. Strategies are discussed on how to increase the short circuit current density beyond 30 mA/cm². In particular, the influence of plasmonic losses of the textured silver (Ag) reflector on the short circuit current and quantum efficiency of the solar cell is discussed. Finally, solar cell structures with reduced plasmonic losses are proposed. Copyright © 2015 John Wiley & Sons, Ltd.