Mixing properties of mim diodes in the infrared

Point contact MIM diodes of different materials have been tested as harmonic mixers at 29 THz and 88 THz. From the analysis of the I-V static characteristic quantitative informations have been obtained about the effectiveness of the diodes as high order mixers.     

Hole arrayed metal-insulator-metal structure for surface enhanced Raman scattering by self-assembling polystyrene spheres

A fabrication process based on the self-assembling polystyrene spheres is proposed to obtain hole arrayed metal-insulator-metal （HA-MIM） structure for surface enhanced Raman scattering （SERS）. The localized field enhancement aroused by the gap resonance in the HA-MIM structure is analyzed by finite-different time domain （FDTD） method. With reference to the theory result, the structure is experimentally fabricated and the Raman scattering spectrum of rhodamine 6G （R6G） is measured by a miniaturized Raman spectrometer. The results shows that the enhancement factor is 3.85 times higher than the control sample with single layered metal hole array. The fabrication process to obtain the HA-MIM SERS substrate is reproducible, fast, large area and low cost.     

Design of periodic metal-insulator-metal waveguide back structures for the enhancement of light absorption in thin-film solar cells

To increase the absorption in a thin layer of absorbing material (amorphous silicon, a-Si), a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enhance the optical path length of light within the solar cells. The new design can result in broadband optical absorption enhancement not only for transverse magnetic (TM)-polarized light, but also for transverse electric (TE)-polarized light. No plasmonic modes can be excited in TE-polarization, but because of the coupling into the a-Si planar waveguide guiding modes and the diffraction of light by the bottom periodic structures into higher diffraction orders, the total absorption in the active region is also increased. The results from rigorous coupled wave analysis show that the overall optical absorption in the active layer can be greatly enhanced by up to 40%. The designed structures presented in this paper can be integrated with back contact technology to potentially produce high-efficiency thin-film solar cell devices.     

基于金属-电介质-金属波导结构的等离子体滤波器的数值研究

基于金属-电介质-金属波导结构, 提出了一种含双侧多支节型等离子波导滤波器, 采用有限元法研究了其透射特性. 在该结构的透射谱中观察到了基于电磁诱导透明效应的四个窄带透射峰, 并通过模场分布有效阐释了透射谱线中峰值、谷值的产生的物理机理. 数值研究同时表明当每个支节长度线性增加时, 透射峰中心波长也将线性增加. 这一结果可用于指导可调谐、多通道窄带滤波器的设计.     

Novel high-quality Fano resonance based on metal-insulator-metal waveguide with L-shaped resonators

Developing a convenient method that can be routinely applied for ascertaining proportions of different vegetable oils employed in commercial blended edible oils remains a significant challenge. We address this issue by proposing a novel method for detecting volume fraction of different oils based on the fact that these oils are optically transparent and have slightly different indices of refraction at a given temperature and wavelength. Accordingly, we develop a highly sensitive sensor for measuring the index of refraction of oil blends based on Fano resonance spectra obtained using a metal-insulatormetal(MIM) waveguide structure comprising a gapped straight waveguide coupled with two L-shaped resonators. The index of refraction sensitivity and figure of merit of the structure are calculated based on modeling using the finite element method, and the waveguide structure is accordingly optimized by adjusting the different geometric parameters to achieve a high-quality Fano resonance spectrum. The optimized structure achieves an ultra-high refractive index sensitivity of 770 nm/RIU in terms of a refractive index unit(RIU) of 1. Moreover, a highly stable linear relationship is obtained between the refractive index of mixed edible oils and the resonance wavelength. Experimental results demonstrate that the proposed structure can detect slight changes in the volume fractions of the components in blended oils.     

表面等离激元在具有PT对称性的环谐振器中的传输

提出了具有PT对称性的金属-绝缘体-金属波导系统,由两个波导耦合一个环谐振器组成,环谐振器的上臂填充增益介质而下臂填充损耗介质。对表面等离激元在该系统的传输特性进行了研究,结果表明:通过平衡增益介质和损耗介质,PT对称性诱导的透明峰可以被清楚地看到,并且该透明峰具有反相位的特点。     

Design and optimization of a nano-antenna hybrid structure for solar energy harvesting application

A novel hybrid structure with high responsivity and efficiency is proposed based on an L-shaped frame nano-antenna(LSFNA) array for solar energy harvesting application. So, two types of LSFNAs are designed and optimized to enhance the harvesting characteristics of traditional simple electric dipole nano-antenna(SEDNA). The LSFNA geometrical dimensions are optimized to have the best values for the required input impedance at three resonance wavelengths of λres = 10 μm,15 μm, and 20 μm. Then the LSFNAs with three different sizes are modeled like a planar spiral-shaped array(PSSA).Also, a fractal bowtie nano-antenna is connected with the PSSA in the array gap. This proposed hybrid structure consists of two main elements:(I) Three different sizes of the LSFNAs with two different material types are designed based on the thin-film metal–insulator–metal diodes that are a proper method for infrared energy harvesting.(II) The PSSA gap is designed based on the electron field emission proposed by the Fowler–Nordheim theory for the array rectification. Finally,the proposed device is analyzed. The results show that the PSSA not only has an averaged 3-time enhancement in the harvesting characteristics(such as return loss, harvesting efficiency, etc.) than the previously proposed structures but also is a multi-resonance wide-band device. Furthermore, the proposed antenna takes up less space in the electronic circuit and has an easy implementation process.     

High-sensitivity refractive index sensors based on Fano resonance in a metal-insulator-metal based arc-shaped resonator coupled with a rectangular stub

A metal-insulator-metal (MIM)-based arc-shaped resonator coupled with a rectangular stub (MARS) structure is proposed. This structure can generate two tunable Fano resonances originating from two different mechanisms. The structure has the advantage of being sensitive to the refractive index, and this feature makes it favorable for application in various microsensors. The relationship between the structural parameters and Fano resonance is researched using the finite element method (FEM) based on the software COMSOL Multiphysics 5.4. The simulation reveals that the sensitivity reaches 1900 nm/refractive index unit (RIU), and the figure of merit (FOM) is 23.75.     

Metal/insulator/metal junctions for electrochemical surface science

We describe the preparation and characterization of Al-AlO_x-Ag tunnel junctions and calculate the energy distribution of the tunneling hot electrons in the range 0–2.5 eV above the Fermi level of silver. Because the mean free path of the hot electrons is of the order of the thickness of the silver film of the junction, which is at the same time the electrode in contact with an electrolyte, new surface effects can be studied. Hot electrons can be injected into the nonhydrated electron band in water. Hot electrons also cause hydrogen evolution at electrode potentials more positive than the ones needed in common electrochemistry. We observed the emission of hot electrons into silver during transients of hydrogen oxidation at silver and during oxidation of overpotential hydrogen on platinum clusters deposited on the silver electrode. The tunnel current at constant tunnel voltage can be changed by faradaic reactions, but surprisingly also by nonfaradaic reactions; this is assigned to a mesoscopic quantum phenomenon.     

Plasmonically induced reflection in metal-insulator-metal waveguides with two silver baffles coupled square ring resonator

A plasmonic waveguide coupled system that is composed of a square ring cavity and a metal–insulator–metal(MIM)waveguide with two silver baffles is proposed. The transmission and reflection properties of the proposed plasmonic system are investigated numerically using the finite element method. The normalized H_z field distributions are calculated to analyze the transmission mode in the plasmonic system. The extreme destructive interference between light mode and dark mode causes plasmonically induced reflection(PIR) window in the transmission spectrum. The PIR window is fitted using the coupled mode theory. The analytical result agrees with the simulation result approximately. In addition, the PIR window can be controlled by adjusting structural parameters and filling different dielectric into the MIM waveguide and the square ring cavity. The results provide a new approach to designing plasmonic devices.