Optical Transmission Through Multilayered Ultra-Thin Metal Gratings

Optical transmission properties of multilayered ultra-thin metal gratings are numerically studied. The transmission spectrum has a broad stop-band with extremely low transmittance compared to that of a single-layer one for TM polarization. The stop-band is shown to be formed by multiple-interference tunneling and various plasmon resonance processes in ultra-thin-metal and dielectric multilayers. That is on the transmission background of non-apertured metal/dielectric multilayer structures that have low transmission in the long-wavelength range due to destructive multiple-interference tunneling, the transmission is further suppressed in the stop-band by plasmon resonances in the top metal/dielectric layers, e.g., the anti-symmetric bound surface plasmon mode in the ultra-thin metal layer and the gap surface plasmon mode in the metal-sandwiched dielectric layer. High transmission beyond the stop-band is due to coupled gap surface plasmon mode in the entire multilayer structures. Applications of the optical properties of the multilayered ultra-thin metal gratings are suggested for optical filtering (wavelength or polarization selective).     

Tailoring Absorption in Metal Gratings with Resonant Ultrathin Bridges

We present a theoretical analysis of the effects of short range surface plasmon polariton excitation on subwavelength bridges in metal gratings. We show that localized resonances in thin metal bridges placed within the slit of a free-standing silver grating dramatically modify transmission spectra and boost absorption regardless of the periodicity of the grating. Additionally, the interference of multiple localized resonances makes it possible to tailor the absorption properties of ultrathin gratings, regardless of the apertures’ geometrical size. This tunable, narrow band, enhanced–absorption mechanism triggered by resonant, short-range surface plasmon polaritons may also enhance nonlinear optical processes like harmonic generation, in view of the large third-order susceptibility of metals.     

Tunable Absorption of Light via Localized Plasmon Resonances on a Metal Surface with Interspaced Ultra-thin Metal Gratings

We studied optical reflection properties of complex metal (Ag) surfaces with close-interspaced ultra-thin metal gratings. Prominent reflection minima were observed corresponding to enhanced absorption of light. Our analysis convinced us that the period-dependent mode is ascribed to Bloch-wave-like resonances of surface plasmon waves at the overall effective metal surfaces, and the ridge-width-dependent mode to Fabry-Pérot-like resonances of localized surface plasmon waves in micro-/nanocavities defined by regions of the grating ridges. The latter resonance mode is shown highly tunable with variation of the grating ridge width. Such structures may be applied in spectrum resolvable photovoltaic devices, bio-sensing, and studying optical properties of cavity-coupled molecules or functional nanomaterials.     

基于旋转偏振角的线偏振扫描成像方法研究

提出一种基于旋转偏振角的新的偏振光成像方法:改变入射线偏振光偏振角和检偏角,采集样品图像系列,总结出背向散射光2个正交偏振分量的光强差关于入射线偏振光偏振角和检偏角的函数关系式.通过对模拟散射介质,猪肉脂肪,猪肉骨骼肌和牛肉骨骼肌等样品进行实验,论证了偏振差函数式中各个参数与样品光学特性之间的联系,并从中提取出2个相互独立的参数,分别表征样品的纤维方向角和光学各向异性度,从而实现对样品浅表层光学特性进行定量测量.和普通光强图像相比,用这些独立的光学信息生成不同基色的图像,能更直观明了地区分组织结构差异,具有潜在的临床医学应用价值,如成为一种皮肤疾病、皮肤损伤的检测方法.     

Investigation of Plasmonic Bandgap for 1D Exposed and Buried Metallic Gratings

Plasmonics - A simulation study for the opening of plasmonic bandgap (PBG) with control over it by varying the slit width (SW) for exposed and buried 1D metallic gratings has been reported by using...     

Investigation of Optical Spectrum Properties of Hexagonal Boron Nitride from Metal to Dielectric Transition

Plasmonics - Hexagonal boron nitride as a natural hyperbolic material has attracted lots of attention recently. Here, we investigate numerically the optical spectrum properties of hexagonal boron...     

Plasmon-Induced Nearly Null Transmission of Light Through Gratings in Very Thin Metal Films

Based on numerical simulations, we show that a very thin metal (Ag) film, otherwise transmissive partially, becomes opaque for transverse magnetic-polarized light in a certain spectrum band when perforated with grating-like slits. Positions of the nearly null transmission band are dependent on the various structure dimensions, particularly on the ridge width for gratings with relatively narrow slit width. Our analyses show that the nearly null transmission is related to resonant excitation of anti-symmetric bound surface plasmon waves at the ridges of the thin metal film gratings and further resulted from destructive interference of waves evolved from the fields at the ridges and slits that are in opposite phase. It is also found that for 2D gratings, the nearly null transmission band appears only for disk array-type gratings and not for the hole array-type gratings. This structure may be applied in novel photonic devices to enhance their performances and functionalities.     

Polarization Splitter with Optical Bistability in Metal Gap Waveguide Nanocavities

A polarization splitter is proposed and numerically investigated. It is composed of two same structures with different arrangement, which is a kind of metal-dielectric nanocavity filling a piece of nonlinear optical material into metal gap waveguides for each. This device with optical bistability based on surface plasmon provides a new way to manipulate light by tuning the incident light intensity and will be essential for the coming optical information processes.     

Plasmonic Optical Properties and Applications of Metal Nanostructures

In this review article, we provide an overview of recent research activities in the study of plasmonic optical properties of metal nanostructures with emphasis on understanding the relation between surface plasmon absorption and structure. Both experimental results and theoretical calculations have indicated that the plasmonic absorption strongly depends on the detailed structure of the nanomaterials. Examples discussed include spherical nanoparticles, nanorods, nanowires, hollow nanospheres, aggregates, and nanocages. Plasmon–phonon coupling measured from dynamic studies as a function of particle size, shape, and aggregation state is also reviewed. The fascinating optical properties of metal nanostructures find important applications in a number of technological areas including surface plasmon resonance, surface-enhanced Raman scattering, and photothermal imaging and therapy. Their novel optical properties and emerging applications are illustrated using specific examples from recent literature. The case of hollow nanosphere structures is highlighted to illustrate their unique features and advantages for some of these applications.     

Photonic Crystal Fiber Polarization Filter Based on Coupling Between Core Mode and SPP Mode

Plasmonics - A polarization filter at the two communication windows of 1.31 and 1.55 μm based on photonic crystal fiber (PCF) coated by nanoscale gold film is proposed. The effects of...     

Polarization Properties of Selectively Gold-filled Suspended Core Microstructured Optical Fibers

We study the polarization properties of suspended core microstructured optical fibers (SC-MOFs) with hexagonal lattice structure and high air-filling fraction having a single gold-filled hole along the horizontal axis. The interaction between the core-guided light and metal leads to surface plasmon resonance (SPR) at particular frequencies where the phase-matching condition is satisfied. We observe from the modal analysis that MOFs with high air-filling fraction offer the possibility of coupling of the fundamental mode with the first-order surface plasmon polariton (SPP) mode. With the increase in the suspension factor (SF), the fundamental mode couples with higher order SPP modes and the coupling strength also enhances. It also leads to an increase in modal birefringence. Reduction in beat length by an order of magnitude compared to the reported values is being reported for the first time to our knowledge. We have achieved the lowest beat length of 0.0105 mm at 1 μm wavelength for the structure having d/Λ = 0.85 and SF = 1.65. The results show that such plasmonic SC-MOFs may perform as efficient in-fiber polarizers and polarization filters.

     

A Polarization Filter Based on Photonic Crystal Fiber with Symmetry Around Gold-Coated Holes

We propose a modified design for a photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR). The air holes are arrayed in diamond lattices, and the diameter of the holes around the gold-coated holes are different that can separate the refractive index of the x-polarization and y-polarization second order surface plasmon polariton (SPP) modes. The influences of structural parameters of the photonic crystal fiber (PCF) on the filter characteristics are studied using the finite element method (FEM). Great changes have taken place in the results of numerical simulation by changing the thickness of the gold film and air hole diameter. Simulation results show that the resonance wavelength is communication wavelength 1550 mm, the loss of the y-polarization mode is 43,126.7 dB/m. When the length of the fiber is 500 μm, extinction ratio is more than 20 dB at the communication wavelength, and bandwidth achieve to 190 nm. It is an important property of PCF polarization filter in production.     

A Polarization Filter Based on Photonic Crystal Fiber with Asymmetry Around Gold-Coated Holes

We propose a modified design for a photonic crystal fiber (PCF) filter based on surface plasmon resonance(SPR). The air holes are arrayed in rectangular lattices, while the size and the pitches of holes around the gold-coated holes are different. That can separate the x-polarization and y-polarization of second-order surface plasmon polariton (SPP). The resonance strength of the surface plasmon mode and import of structural parameters of the PCF on the filter characteristics are studied through using the finite element method (FEM). Numerical simulations demonstrate that the thickness of the gold layer, the gold-coated or gold-filled, and the asymmetry around the gold-coated holes have a great effect on the filter characteristics. It is certain to obtain a resonance strength as high as 873 and 771.5 dB/cm at the communication wavelength of 1050 and 1310 nm in x-polarization by adjusting the size and the place of the gold-coated holes, while the loss is extremely low in y-polarization.     

Polarization Optical Properties of the Pancreatic Acinar Cell of the Mouse

The birefringence of fresh and fixed mouse pancreatic acinar tissue was studied, utilizing whole mounts of pancreas from which the mesentery had been removed. Fresh pancreas in Tyrode's solution demonstrated positive birefringence with respect to the radial axis (the axis radiating from the nucleus as spokes from a wheel). Formol fixation reversed the sign of birefringence to negative with respect to the radius. The magnitude of birefringence increased with longer fixation. Neutral formol also reversed the sign to radially negative, but the magnitude did not increase with longer fixation. Tissue fixed in 2 per cent osmium tetroxide or potassium permanganate demonstrated strongly negative birefringence with respect to the radius. The cytoplasm of tissue fixed in acetic acid, though finely granular, still possessed radially positive birefringence. Birefringent areas could be seen in tissue fixed in potassium dichromate, but the sign of birefringence could not be determined. Ethyl alcohol, chromic acid, picric acid, and mercuric chloride all produced a brilliant cytoplasm in which no birefringence could be demonstrated. Freezing markedly decreased the radially positive birefringence of fresh tissue. Fresh tissue placed in increasing concentrations of glycerol demonstrated increasing radially positive birefringence. When formol-fixed tissue was placed in glycerol, the radially negative birefringence decreased. Osmium tetroxide-fixed tissue in 50 per cent glycerol was isotropic. The granularity of ethyl alcohol-fixed tissue disappeared in 50 per cent glycerol, and radially positive birefringence was evident. Frozen tissue showed increasing radially positive birefringence in increasing concentrations of glycerol. The results are discussed in relation to theories of fixation.     

A Kind of Broadband Polarization Filter Based on Photonic Crystal Fiber with Nanoscale Gold Film

Plasmonics - A kind of polarized filtering photonic crystal fiber (PCF) with nanoscale gold film is studied by using the finite element method. The cross-section structure of the PCF is composed of...     

Compatibility of Temperature Sensor and Polarization Filter Based on Au Film and Glycerin Selectively Infilling Photonic Crystal Fibers

The Au film and glycerin selectively infilling photonic crystal fibers are analyzed by the finite element method. One cladding air hole is coated with Au film and infiltrated with glycerin to form a defect core. The simulation results show that both of the defect core modes formed on the glycerin and Au film can inspire resonance with core modes. The maximum sensitivity can reach to 2.50 nm/ ^°C in x polarized direction and 2.00 nm/ ^°C in y polarized direction for the temperature sensor, respectively. Furthermore, we obtain that the confinement losses of the photonic crystal fibers (PCFs) can meet with 321.442 dB/cm and 445.958 dB/cm at a short wavelength band (1460 ～1530 nm) and an extended wavelengths band (1360 ～1460 nm) for x polarized direction and y polarized direction respectively, which can be applied in many polarization filter devices as well. The compatibility of temperature sensor and polarization filter based on an identical structure can be realized at different wavelengths.     

Surface Plasmon Induced Polarization Filter Based on Au Wires and Liquid Crystal Infiltrated Photonic Crystal Fibers

The polarization filter characteristics of Au wires and liquid crystal infiltrated photonic crystal fibers are investigated by using the finite element method. The nematic liquid crystal of E7 being injected into cladding air holes is benefit to induce large birefringence under controllable electrical field. The simulation results show that the surface plasmon resonance is strongly inspired by core modes in y-polarized direction. Meanwhile, the coupling between core modes in x-polarized direction and surface plasmon polaritons modes is faint. The confinement losses can achieve 446 dB/cm in y-polarized direction and 0.8 dB/cm in x-polarized direction at wavelength of 1550 nm in one of our designed fiber. The effects of fiber structural parameters and temperature are investigated with a view of tuning and optimizing the confinement loss spectrum. Own to the large contrast of confinement losses in two orthogonal directions, the designed Au wires and liquid crystal infiltrated photonic crystal fibers promise candidate for tunable polarization filter devices.     

Purification and Some Properties of Metal Proteinases from Lentinus edodes

To investigate the function of proteinases in the fruiting of Basidiomycetes, we purified the neutral proteinase in vegetative mycelium of Lentinus edodes. About 1.6 mg of purified enzyme was obtained from 1.5 kg of mycelium. The purified enzyme was confirmed to be monodispersive on disc electrophoresis.

The neutral proteinase was most active around pH 7.5 toward hemoglobin and 7.0 toward casein and was extremely labile with temperature. The enzyme was strongly inhibited by EDTA or Talopeptin (MK-I). The molecular weight and isoelectric point of the enzyme were 45,000 and pH 5.3, respectively. The enzyme contained no methionine residues. The enzyme hydrolyzed the bonds involving hydrophobic or bulky amino acid residues of oxidized insulin B-chain such as His-Leu (10–11 and 5–6), Leu (17)-Val (18) and Ala (14)-Leu (15).

These characteristics are compared with those of the metal proteinase in the fruit-body of the same fungus, which was purified and characterized at the same time as in vegetative mycelium. We also compare it with proteinases from other microbes.     

Surface Plasmon Induced Polarization Splitting Based on Dual-Core Photonic Crystal Fiber with Metal Wire

The polarization characteristics of a dual-core photonic crystal fiber (PCF) with a metal wire filled into the cladding air hole between the two cores have been investigated. Numerical investigation shows that the inclusion of the metal wire greatly changes the coupling characteristics of the modes in the two cores. In fact, the coupling lengths of the two polarizations show increased difference, which leads to the possibility of designing a dual-core PCF with a coupling length ratio of 1:2 for the two polarization states. The proposed polarization splitter shows extinction ratios as low as ?20 dB with bandwidths as great as 146 nm.