从光子晶体效应到表面等离子波的实时演变

文章报道了激光诱导太赫兹表面等离子谐振效应。采用激光抽运-太赫兹波探测技术,实时改变单晶硅中的载流子浓度,使其介电特性从类绝缘体演变为类金属导体,以支持表面等离子谐振效应,进而实现太赫兹波在周期性亚波长单晶硅孔阵列中的实时可控制谐振增强传输。同时还通过实验观测到太赫兹波从光子晶体效应到表面等离子波的实时演变。文章作者采用Fano模型对实验结果进行模拟分析,获得了与实验数据一致的理论拟合。     

太赫兹波段表面等离子光子学研究进展

表面等离子光子学是研究金属、 半导体纳米结构材料独特的光学特性, 是目前光子学中最有吸引力、 发展最快的领域之一. 伴随着微/纳制造技术与计算机模拟技术的进步, 表面等离子光子学在可见光、 红外、 太赫兹以及微波频域得到了广泛研究, 在高灵敏生化传感、 亚波长光波导、 近场光学显微、 纳米光刻等领域有潜在的应用价值. 特别是人工超材料的发展, 为自然界长期缺乏响应太赫兹波的材料和器件奠定了基础, 从而也促进了太赫兹波段表面等离子光子学的研究. 本文从太赫兹表面等离子波的激发、 传导、 最新应用及未来发展趋势等几个方面进行了回顾和讨论, 将最新研究成果展示给读者.     

碳纳米管薄膜周期结构的太赫兹表面等离子波特性研究

在获得太赫兹波段碳纳米管薄膜的介电特性基础上,利用数值THz时域光谱技术研究了碳纳米管薄膜栅周期结构的表面等离子激元的传播特性和局域化现象. 研究结果表明,在栅周期为168 μm时,频率在0.5-2.5 THz之间出现两个等离子模式的共振峰值,分别位于0.99 THz和1.95 THz,这与理论计算结果相符合. 数值计算的表面等离子激元传播距离与理论预测值相一致,达到了146 μm. 此外,分析了栅厚度与栅宽度变化对表面等离子波特性的影响. 关键词： 太赫兹 碳纳米管 表面等离子波     

光子晶体对太赫兹波的调制特性研究

利用传输矩阵方法研究了掺杂半导体n-GaAs/聚碳酸脂一维光子晶体的太赫兹波透射谱.研究结果发现,与一般由两种介电材料组成的一维光子晶体不同,由于掺杂半导体中自由载流子对太赫兹波存在较强的吸收,所以这种材料组成的一维光子晶体除可形成光子带隙外,还可以增强n-GaAs对太赫兹波的透射.同时还提出了一种基于这种一维光子晶体的太赫兹波调制器,通过外加电压控制半导体中电子浓度的大小可实现对太赫兹透射波幅度的调制. 关键词： 掺杂半导体光子晶体 太赫兹波 太赫兹波的调制     

基于人工复合材料的太赫兹波双波段滤波

本文分别从实验和理论模拟两方面详细的讨论了金属双环和反双环两种亚波长阵列结构在太赫兹波段的双频率响应特性. 这两种双环结构都可以实现双频率调制,金属双环结构表现为两个明显的吸收峰,反双环结构则表现出明显的透过峰. 这两种结构不仅在物理结构上互补,在太赫兹波段的响应也表现为吸收和透过互补的特性. 其中高频响应来源于内环电子振荡,低频影响则来源于外环电子振荡,并且这种结构在太赫兹波段的响应与周期无关. 关键词： 太赫兹 滤波器 亚波长阵列 FDTD     

介质填充浅槽周期结构表面上的太赫兹表面等离子体激元

通过在金属表面刻成浅的垂直凹槽,并在槽内填充不同的介质,对金属表面浅槽周期结构上传播的表面等离子体激元的色散特性与填充介质的关系进行了研究.研究表明通过在周期凹槽内填充介质可以有效降低人工表面等离子体激元的渐近频率,并增强金属表面对电磁场的约束.分析了太赫兹波段金属的吸收损耗对人工表面等离子体激元特性的影响,结果显示基于填充介质的浅槽周期表面结构可以获得长距离传输以及场的亚波长约束.通过对波传输的数值仿真,验证了该表面结构在太赫兹波段良好的导波能力.这种表面结构对太赫兹波段新型集成导波器件的设计具有参考价值.     

介质填充浅槽周期结构表面上的太赫兹表面等离子体激元

通过在金属表面刻成浅的垂直凹槽,并在槽内填充不同的介质,对金属表面浅槽周期结构上传播的表面等离子体激元的色散特性与填充介质的关系进行了研究.研究表明通过在周期凹槽内填充介质可以有效降低人工表面等离子体激元的渐近频率,并增强金属表面对电磁场的约束.分析了太赫兹波段金属的吸收损耗对人工表面等离子体激元特性的影响,结果显示基于填充介质的浅槽周期表面结构可以获得长距离传输以及场的亚波长约束.通过对波传输的数值仿真,验证了该表面结构在太赫兹波段良好的导波能力.这种表面结构对太赫兹波段新型集成导波器件的设计具有参考价值.     

亚波长金属块阵列中太赫兹波的传输特性研究

利用太赫兹时域光谱技术,研究了亚波长金属块阵列的太赫兹透射光谱特性及金属阵列结构的周期、金属块尺寸等因素对太赫兹透射特性的影响.结合时域有限差分方法,对实验结果进行了数值模拟,并分析了影响太赫兹透射的因素.结果表明:亚波长金属块阵列结构中,THz波的透射极小的位置由金属块的尺寸和周期决定,其透射谷的半高宽随其周期的增大而减小;透射峰值的位置由阵列的周期结构决定,其频率随周期的增加而减小;亚波长金属块结构的透射极小来源于金属块表面局域化电场等离子体的本征频率反射,该局域化电场与金属块结构密切相关,通过改变金属块结构,可以改变其表面电场分布与局域化.研究结果为研制太赫兹波段带阻滤波器提供了有益的参考.     

亚波长金属块阵列中太赫兹波的传输特性研究

利用太赫兹时域光谱技术,研究了亚波长金属块阵列的太赫兹透射光谱特性及金属阵列结构的周期、金属块尺寸等因素对太赫兹透射特性的影响.结合时域有限差分方法,对实验结果进行了数值模拟,并分析了影响太赫兹透射的因素.结果表明:亚波长金属块阵列结构中,THz波的透射极小的位置由金属块的尺寸和周期决定,其透射谷的半高宽随其周期的增大而减小;透射峰值的位置由阵列的周期结构决定,其频率随周期的增加而减小;亚波长金属块结构的透射极小来源于金属块表面局域化电场等离子体的本征频率反射,该局域化电场与金属块结构密切相关,通过改变金属块结构,可以改变其表面电场分布与局域化.研究结果为研制太赫兹波段带阻滤波器提供了有益的参考.     

基于光子晶体的双波长太赫兹波功分器研究

太赫兹波技术和光子晶体技术相结合为设计太赫兹波功能器件提供了新的思路和方法.本文提出了一种基于二维光子晶体的双波长太赫兹波功分器.在光子晶体中引入由三个相互平行的单模波导形成的定向耦合型分束器和Y型结构的1×2型分束器,同时,在Y型结构的分支处分别引入两个介质柱.利用平面波展开法和定向耦合原理计算了在不同入射波频率下,耦合波导的耦合长度,并采用时域有限差分法对功分器的传输特性进行了模拟仿真分析.结果表明,在频率f1=1.0THz时,实现了端口1和端口2的能量均分输出;在频率f2=0.893THz时,通过非对称改变两个介质柱的折射率,可以实现端口3和端口4输出能量的自由分配.     

High sensitivity refractive index gas sensing enhanced by surface plasmon resonance with nano-cavity antenna array

The surface plasmon resonance gas sensor is presented for refractive index detection using nano-cavity antenna array.The gas sensor monitors the changes of the refractive index by measuring the spectral shift of the resonance dip,for modulating the wavelength of incident light.It is demonstrated that minute changes in the refractive index of a medium close to the surface of a metal film,owing to a shift in the resonance dip of the wavelength,can be detected.The average detection sensitivity is about 3200 nm/RIU(refractive index units),which is more than twice that of a metal grating-based gas sensor.The reflectivity of the surface plasmon resonance dip is only ～ 0.03%,and the full widths at half maximum(FWHMs) of bandwidth of the angle and wavelength are ～ 0.20° and 4.71nm,respectively.     

Direct observation of a transition of a surface plasmon resonance from a photonic crystal effect

Transition of surface-plasmon resonance from out-of-plane photonic crystal effect is observed in a semiconductor array of subwavelength holes by optical pump-terahertz probe measurements. The dielectric properties of the photoexcited array are essentially altered by the intense optical excitation due to photogenerated free carriers. As a result, the array becomes metallic and favors the coupling and propagation of surface plasmons. The photoinduced resonant extremes agree well with the Fano model.     

Highly sensitive selectively coated D-shape photonic crystal fibers for surface plasmon resonance sensing

We propose a design for a high sensitivity plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) and analyze the sensor using finite element software (FEM). By introducing a D-shape hole instead of a circular hole in the first ring of the photonic crystal fiber, which increases the coupling effect and proficient infiltration of the sensing, resulting in enhance the performance of the sensor due to the flat structure of the D-shape hole and the homogeneous metal coating facility. We study the influence of the parameters of the D-shape hole on the sensing performance and analyze the sensor performance based on the wavelength and amplitude sensitivity. The results show that the proposed sensor is capable of detecting analyte refractive index ranging from 1.30 to 1.42, and the maximum sensitivities of 14,600 nm/RIU and 1475 RIU^?1 can be achieved in this sensing range, respectively. The largest sensor resolutions for wavelength and amplitude sensing are $6.84\times {10}^{?6}$ and $6.78\times {10}^{?6}\text{ RIU}$, and the maximum figure of merits (FOM) of the proposed sensor being 618.     

表面等离子体亚波长光学前沿进展

目前表面等离子体激元(surface plasmon polaritons，SPPs)在光存储、光激发、显微术以及生物光子学等领域中的应用前景受到了广泛的关注．文章介绍了SPPs的基本性质和表面等离子体亚波长光学(surface plasmons subwavelength optics)研究中的热点问题及发展方向．     

The influence of hole shape on enhancing transmission through subwavelength hole arrays

The extraordinary light transmission through a 200-nm thick gold film when passing through different subwavelength hole arrays is observed experimentally. The sample is fabricated by electron beam lithography and reactive ion etching system. A comparison between light transmissions shows that the hole shape changing from rectangular to diamond strongly affects the transmission intensity although both structures possess the same lattice constant of 600,nm. Moreover, the position of the transmission maximum undergoes a spectral red-shift of about 63,nm. Numerical simulations by using a transfer matrix method reproduce the observed transmission spectrum quite well.     

基于导模共振效应提高石墨烯表面等离子体的局域特性

本文构建了一种包含石墨烯和亚波长光栅的复合结构, 借助衍射光栅的导模共振效应, 在石墨烯表面激发高局域性表面等离子体激元, 研究了石墨烯与光栅结构对表面等离子体激元局域特性的影响规律, 并借助基于有限元法的COMSOL软件, 分析了缓冲层厚度、光栅周期、载流子迁移率和费米能级对石墨烯的表面电场、品质因子Q和有效模式面积S_eff的影响. 结果表明, 石墨烯表面等离子体激元的局域性在特定的参数点获得显著提高: 当μ = 0.7 m²/(V·s)时, 品质因子达到最大值Q_max = 1793; 当p = 235 nm或E_F = 0.72 eV时, 表面电场达到了入射光的3000倍以上. 强烈的局域性导致强烈 的光-物质相互作用, 因而本文提出的复合结构可实现高灵敏度传感器和高效率的非线性光学设备, 极大地扩展了石墨烯在纳米光学领域中的应用.     

Compact surface plasmon amplifier in nonlinear hybrid waveguide

Surface plasmon polariton(SPP), a sub-wavelength surface wave promising for photonic integration, always suffers from the large metallic loss that seriously restricts its practical application. Here, we propose a compact SPP amplifier based on a nonlinear hybrid waveguide(a combination of silver, LiNbO_3, and SiO_2), where a couple of Bragg gratings are introduced in the waveguide to construct a cavity. This special waveguide is demonstrated to support a highly localized SPP-like hybrid mode and a low loss waveguide-like hybrid mode. To provide a large nonlinear gain, a pumping wave input from the LiNbO_3 waveguide is designed to resonate inside the cavity and satisfy the cavity phase matching to fulfill the optical parametric amplification(OPA) of the SPP signal. Proper periods of gratings and the cavity length are chosen to satisfy the impedance matching condition to ensure the high input efficiency of the pump wave from the outside into the cavity. In theoretical calculations, this device demonstrates a high performance in a very compact scheme(~3.32 μm) and a much lower pumping power for OPA compared with single-pass pumping. To obtain a comprehensive insight into this cavity OPA, the influences of the pumping power, cavity length, and the initial phase are discussed in detail.     

准晶体结构光纤表面等离子体共振传感器特性研究

光纤表面等离子体共振传感器在高灵敏度传感和在线实时监测等领域具有重要意义. 设计了一种六重准晶体结构环形通道光纤表面等离子体共振传感器, 基于有限元法对该传感器的传感特性进行了数值模拟. 研究了光纤各结构参量对传感器特性的影响规律. 研究结果表明: 待测液折射率的有效监测范围为1.25–1.331, 最高灵敏度可达26400 nm·RIU^-1, 传感器具有损耗谱杂峰少、探测范围广、灵敏度高、设计灵活性高和光路可弯曲等特点, 在生化检测、公共安全、环境污染监测以及高灵敏度传感等领域具有广泛的应用前景.     

Polarization-insensitive surface plasmon resonance sensor by cross-slit metallic periodic arrays

We propose a plasmonic structure to obtain polarization-insensitive localized surface plasmon resonance (LSPR) sensor, which consists of cross-slit metallic periodic arrays embedded in the background material. Numerical simulation illustrates that the mechanism of the LSPR sensor is based on the shift of the Fabry–Perot cavity mode resonance peak in the spectrum as the change of the dielectric material properties for the near fields. And one of the transmission dips of the structure is very sensitive to the background materials; the structure could gain the sensitivity (nm/RIU) more than 500 nm/RIU. Meanwhile, the structure holds great potential to achieve high-performance sensors in practical application due to polarization-insensitive virtue.