混合表面等离子体光子晶体波导

构建了一种金属-绝缘体-半导体混合表面等离子体结构,基于时域有限差分法验证了该结构在归一化频率0.243~0.271 (a/λ) 范围内具有明显的TM模式带隙。在二维光子晶体层移除或改变中间行空气孔半径构成线缺陷,形成混合波导结构1和2。分析表明,入射光频率位于带隙内的光子能量被很好的局域在低折射率层中,且只能沿线缺陷传输。当入射波长为1550nm时,两种波导的传输距离分别为18.41μm和15.70μm,群速度极值分别为0.186c和0.166c,品质因数FoM达到384.74和1042.50。此波导能通过光子晶体层的线缺陷控制低折射率层SPP的传输路径,为波导器件的研究提供了有效的理论基础和依据。     

Manipulation and Steering of Hyperbolic Surface Polaritons in Hexagonal Boron Nitride

Hexagonal boron nitride (hBN) is a natural hyperbolic material that supports both volume‐confined hyperbolic polaritons and sidewall‐confined hyperbolic surface polaritons (HSPs). In this work, efficient excitation, control, and steering of HSPs are demonstrated in hBN through engineering the geometry and orientation of hBN sidewalls. By combining infrared nanoimaging and numerical simulations, the reflection, transmission, and scattering of HSPs are investigated at the hBN corners with various apex angles. It is also shown that the sidewall‐confined nature of HSPs enables a high degree of control over their propagation by designing the geometry of hBN nanostructures.     

Exploring Plasmonic Resonances Toward “Large-Scale” Flexible Optical Sensors with Deformation Stability

The next generation of sensors requires a simple yet compact lab on chip-based precise optical detection mechanism where data interpretation can be achieved with minimum effort. Hereby, cost-efficient strategies of manufacturing both propagating surface plasmon polariton (SPP) and localized surface plasmon resonance (LSPR) sensors on flexible platforms are explored via mechanical instabilities and oblique-angled metal evaporation. Centimeter scaled dielectric grating structures produced by plasma oxidation of pre-stressed polydimethylsiloxane film have comprised the substrates, thus imparting inherent flexibility. Subsequently, both continuous and discontinuous 1D-metallic lattices are obtained via vapor deposition of gold at different angles. The optical isotropy (gold surface-grating) and anisotropy (gold edge-grating) are distinctly observed as a difference between forward and backward diffraction efficiencies, backed by analytical correlation to the observed orders. Supported with electromagnetic modeling, the SPP and LSPR excitations are experimentally characterized under reflectance and transmittance measurements, along with a demonstration of their sensing capabilities. The LSPR supported flexible sensor provides superiority in terms of sensitivity, which is investigated under mechanical deformations to exhibit consistency of the resonant wavelength. Such consistency is strategically unraveled via “finite element method” based approaches, thus providing a new paradigm of cost-efficient, large-scaled flexible sensors.     

Anatomical analysis of the light transmission through a single subwavelength metal slit by the FDTD method

Transverse-magnetic (TM) polarized light transmission through a single subwavelength metal slit is re-examined with finite-difference time-domain (FDTD) simulations. In contrast to previous studies, we derive an anatomical view of the electromagnetic field distribution in different cross-sections and emphasize the generation of a field coupling mode in the slit. Numerical modeling reveals that both peak and dip transmissions are features of the field interference in the slit. The slit width and depth are mainly responsible for establishing the amplitude and phase, respectively, of the coupled mode. Moreover, it is found that the output energy dispensation between the radiative and surface components is actually determined by the slit width. Analysis of the physical properties of the slit, including the coupled mode structure in the transverse plane, the effective refractive index and Ohmic absorption losses, provides new insights into the light transmission processes.     

Propagation properties of an elliptical anisotropic metamaterial cylinder

The propagation characteristics were investigated of an open elliptical cylinder comprising a uniaxial anisotropic metamaterial. The dispersion relation for hybrid modes in this cylinder was examined theoretically. It is shown that forward and backward waves can be supported by such a metamaterial cylinder. Even and odd modes have different losses in a realistic anisotropic elliptical cylinder. The forward wave can propagate longer distances than the backward wave because of its lower loss. The light can propagate backward on the cylinder without the limit of structure size. The odd modes have higher operating wavelengths than the even modes. The extraordinary properties in this structure are identified as multilayer plasmons. The validity of the effective medium approximation of this structure is examined.     

Dual wavelength demultiplexer based on metal–insulator–metal plasmonic circular ring resonators

Abstract

In this paper, we investigated a plasmonic demultiplexer structure based on Metal–Insulator–Metal (MIM) waveguides and circular ring resonators. In order to achieve the structure of demultiplexer, two improved ring resonators have been used, which input and outputs MIM waveguides coupled by the ring resonators. To improve the transmission efficiency, a reflector was introduced at the right end of the input and output waveguides. By substituting the ring core with dielectric, the possibility of tuning the resonance wavelength of the proposed structure is illustrated, and the effect of various parameters such as radius and refractive index in transmission efficiency is studied in detail. This is useful for the design of integrated circuits in which it is not possible to extend the dimension of the ring resonator to attain a longer resonance wavelength. Transmission efficiency and quality factor of the single ring are 84% and 110, respectively. The simulation results using finite difference time domain method shows that in the proposed demultiplexer, which is composed of two rings with different core refractive indexes, the average power efficiency, bandwidth for each output channel, and the mean value of crosstalk are estimated 80%, 17 nm, and ?26.95 dB, respectively. It is revealed that the significant features of the device are high transmission efficiency, low crosstalk, high-quality factor, and tunability for desired wavelengths. Therefore, the proposed structure has the potential to be applied in plasmonic integrated circuits.     

硅棱镜耦合输出THz波参量振荡器的实验研究

利用一块MgO:LiNbO3晶体,采用Si棱镜耦合出射方式构成太赫兹(THz)波参量振荡器,实现了高效可调谐的THz波输出,调谐范围为0.95～2.10THz。在1.80THz处,当泵浦能量为101mJ时,产生的THz波平均功率为580nW,THz波单脉冲能量为58nJ,THz波能量转换效率为5.74×10-7;同时产生的Stokes能量为2.7mJ。实验中,观察到了一阶和二阶Stokes光,一阶Stokes光与泵浦光的频差等于产生的THz波的频率。     

填充比对金属光栅与介质光栅激发表面等离子波的不同影响

采用严格耦合波理论求解了不同填充比的金属光栅与金属平面覆盖介质光栅在角度调制下的共振衰减反射谱,以及它们在表面等离子体共振时的空间场分布,并对结果进行了对比分析。通过数值计算分析了金属表面等离子体波（Surface Plasmon Polariton, SPP）波矢的有效折射率 与光栅填充比的关系,结果表明对于Au金属光栅结构,SPP的 随着光栅填充比增加并无明显变化;而对于金属平面覆盖介质光栅结构,SPP的 随着介质光栅的填充比的增大单调递增。