A Polarization Filter Based on a Novel Photonic Crystal Fiber with a Gold-Coated Air Hole by Using Surface Plasmon Resonance

A novel design of a polarization filter based on photonic crystal fiber (PCF) is proposed in this paper. With the introduction of a gold-coated air hole, the resonance strength is much stronger in y-polarized direction than in x-polarized direction at some particular wavelengths, which is due to the metal surface plasmon effects. At the wavelength of 1.31 μm, the loss of y-polarized mode is 2138.34 dB/cm while the loss is very low in x polarization. Furthermore, the loss peak can be flexibly adjusted from the wavelength of 1.26 to 1.56 μm by changing the thickness of a gold layer, and the loss in y polarization can be kept above 1200 dB/cm. The significant loss in y polarization makes this PCF a good candidate for developing a polarization filter with high performance.     

Design of a Single-Polarization Single-Mode Photonic Crystal Fiber Filter Based on Surface Plasmon Resonance

We design a single-polarization single-mode photonic crystal fiber filter based on surface plasmon resonance. The finite element method is employed to evaluate the characteristics of the filter. The proposed fiber is devised such that there is a great discrepant confinement loss between two polarizations of x and y by varying two air holes in the cladding region, which is composed of hexagonal structural air holes in pure silica selectively filling with gold wires. Numerical simulations show that single-polarization single-mode operation waveband can be tuned by adjusting the parameters of the photonic crystal fiber. The confinement losses of the unwanted polarization can reach to 126.10 and 326.30 dB/cm in the wavelengths of 1.31 and 1.55 μm, while the corresponding confinement losses of the wanted polarized mode are only 0.08 and 1.20 dB/cm, respectively. Furthermore, the crosstalk can come to a maximum of 120.34 and 310.41 dB in the two communication bands. The bandwidths of the fiber designed for 1.31 and 1.55 μm are, respectively, 20 and 60 nm, which may be found useful applications for fiber polarizer.     

Plasmonic Broadband Polarization Splitter Based on Dual-Core Photonic Crystal Fiber with Elliptical Metallic Nanowires

We design two kinds of plasmonic broadband polarization splitters based on dual-core photonic crystal fiber (DC-PCF) with elliptical Au or Ag nanowire in this paper. It is analyzed for the polarization independent characterestics of the designed DC-PCF by the finite element method (FEM). In order to excite the surface plasmon resonance (SPR), the metal Au and Ag are filled into elliptical central air hole. The resonance coupling between the fourth- or fifth-order surface plasmon modes (SPMs) and core-guided modes (CGMs) are founded by this numerical simulation. The device lengths of the designed splitters with Au nanowire are 2937 and 827 μm at the wavelength of 1.31 and 1.55 μm, respectively. As the extinction ratios are better than ?20 dB, its bandwidths are better than 94 and 103 nm. For the designed Ag nanowire splitter, the device lengths are 3066 or 809 μm at 1.31 or 1.55 μm, respectively. The bandwidths with the extinction ratio better than ?20 dB are 66 and 104 nm, respectively.     

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.     

Enhancement of Emission Efficiency of Deep-Ultraviolet AlGaN Quantum Wells Through Surface Plasmon Coupling with an Al Nanograting Structure

The enhancement of the internal quantum efficiency (IQE) of deep-ultraviolet Al _x Ga_1-x N/Al _y Ga_1-y N (x < y) quantum wells (QWs) by fabricating one-dimensional Al nanogratings on a QW structure for inducing surface plasmon (SP) coupling is demonstrated. Through temperature-dependent photoluminescence (PL) measurement, the enhancements of IQE in different emission polarizations are illustrated. Due to the small difference in energy band level between the heavy/light hole and split-off valence bands, the IQEs of the transverse electric- (TE-) and transverse magnetic- (TM-) polarized emissions are about the same. When emission polarization is perpendicular to Al-grating ridges, the SP resonance mode for coupling with the QWs is dominated by localized surface plasmon (LSP). When emission polarization is parallel with Al-grating ridges, the coupled SP resonance mode may mix LSP and SP polariton. In this polarization, LSP can be excited because of the width fluctuation of a grating ridge. When the excitation laser polarization is perpendicular to Al-grating ridges, the strong LSP resonance at the excitation laser wavelength leads to stronger excitation and hence higher IQE levels.     

Simulation of Some Plasmonic Biosensors for Detection of Hemoglobin Concentration in Human Blood

Three recently published plasmonic biosensors based on a birefringent solid-core or a partial-solid-core microstructured optical fiber are simulated for detection of hemoglobin concentration in human blood. For a larger value of the number of holes n _h but for the same value of the gold radius, the resonance spectral width and the difference between maximal amplitude sensitivity and resonant wavelengths are decreased, when the refractive index of the analyte is n _a = 1.357. Also, the loss and maximum of the amplitude sensitivity are increased in the same conditions. At the resonant wavelength λ = 0.6496 μm for the devices with n _h = 14, 17, and 35 holes and n _a = 1.357, the hemoglobin concentration is close to the mean value (157.5 g/l) of a man.     

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.     

Hi-Bi Photonic Crystal Fiber for Broadband Filter Realization Using Copper Microwires

This paper presents a highly birefringence (Hi-Bi) photonic crystal fiber (PCF)-based single-polarization filter, which consists of copper microwires. Copper is chemically stable and the use of microwires is benefit to fabricate than any metal-coated PCF. The filter characteristics are inspected by the full-vector finite element method (FEM). The proposed filter can filter out y-polarized mode, while the x-polarized mode can be guided. The confinement loss of the y-polarized mode at the wavelength of 1.31 μm is achieved of 696.79 dB/cm, while the x-polarized loss is only 4.34 dB/cm. According to numerical results, 20 dB bandwidth of the proposed filter with a maximum value of crosstalk of 601.37 dB is achieved of 650 nm that range from 1.1 to 1.75 μm. Furthermore, the insertion loss of the guided mode (x-polarization) is as low as 0.142 dB for 1 mm of fiber length. Moreover, by optimizing the structural parameters, it has shown that the proposed filter can be effective at any wavelength at the optical communication window.

     

A Photonic Crystal Fiber Polarized Filter at 1.55 μm Based on Surface Plasmon Resonance

A single-polarization photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) is proposed. Finite element method is employed in simulating the PCF with gold-coated. The resonance wavelength can be modulated by changing the thickness of gold layer. At the resonance wavelength 1.55 μm, the loss of y-polarized mode is much larger than the loss of x-polarized mode. When the fiber length is set to 2 mm, the value of extinction ratio reaches to −118.7 dB, the y-polarized mode is suppressed and only x-polarized mode can be guided. The fiber is applicable in the production of single-polarization filter. The PCF has a simple structure and a big error tolerance, it has a good practicability.

     

A Broadband Single Polarization Photonic Crystal Fiber Filter Around 1.55 μm Based on Gold-Coated and Pentagonal Structure

Plasmonics - In this paper, a broadband single polarization photonic crystal fiber (PCF) filter around 1.55&nbsp;μm is presented on account of surface plasmon resonance. The finite element...     

Modulation of Visible and Near-Infrared Surface Plasmon Resonance of Au Nanoparticles Based on Highly Doped Graphene

We study an active modulation of surface plasmon resonance (SPR) of Au nanoparticles based on highly doped graphene in visible and near-infrared regions. We find that compared to the traditional metal SPR, the SPR of Au nanoparticles based on graphene causes a remarkable blue shift. The field intensity in the gap is redistributed to standing wave. The field intensity of standing wave is about one order of magnitude higher than the traditional model. Moreover, the SPR of Au nanoparticles can be actively modulated by varying the graphene Fermi energy. We find the maximum modulation of field intensity of absorption spectra is more than 21.6 % at λ?=?822?nm and the amount of blue shift is 17.4 nm, which is about 2.14 % of the initial wavelength λ ₀?=?813.4?nm, with increasing monolayer graphene Fermi energy from 1.0 to 1.5 ev. We find that the SPR sensitivity to the refractive index n of the environment is about 642 nm per refractive index unit (RIU). The SPR wavelengths have a big blue shift, which is about 33 nm, with increasing number of graphene layers from 1 to 3, and some shoulders on the absorption spectra are observed in the models with multilayer graphene. Finally, we study the Au nanorod array based on monolayer graphene. We find that the blue shift caused by the graphene increases from 14 to 24 nm, with increasing gap g _y from 10 to 20 nm. Then, it decreases from 24 to 14 nm, with increasing gap g _y from 20 to 50 nm. This study provides a new way for actively modulating the optical and optoelectronic devices.     

Highly Sensitive Biochemical Sensor Based on Two-Layer Dielectric Loaded Plasmonic Microring Resonator

In this paper, we propose and design a highly sensitive optical biochemical sensor based on two-layer dielectric loaded surface plasmon polariton waveguide (TDLSPPW)-based microring resonator (MRR). By optimizing the structure parameters, the propagation length of the proposed waveguide is ~126 μm, which is about 3 times of that of the polymer dielectric loaded surface plasmon polariton waveguide (DLSPPW) reported. It is demonstrated that the TDLSPPW-based MRR is operated at the under-coupling state, along with the quality factor (Q) of 541.2 and extinction ratio (ER) of 12.2 dB. Moreover, the Q and ER are much more sensitive to the structure parameters of the waveguide, including the waveguide width w, total thickness t, and coupling gap W _gap, compared to the low refractive index (RI) layer thickness t ₂. The simulation results on the biochemical RI sensing show that the sensitivities of 408.7 and 276.4 nm/RIU for glucose concentration in urine and chemical gases can be achieved, respectively. It is believed that the proposed sensor has potential applications in photonic-integrated biochemical sensing.     

Application of a Plasmonic Biosensor for Detection of Human Blood Groups

A recently published plasmonic biosensor based on birefringent solid-core microstructured optical fiber is applied for the detection of human blood groups. The birefringent behavior is obtained by removing five central air holes of a two-ring hexagonal lattice of holes in a gold-covered silica fiber with the blood layer surrounding the fiber. The sensing performance of two resonant modes (I based on a phase matching point and II based on a loss matching point) are analyzed. For an increase of the refractive index from 1.3768 (human blood group A) to 1.3796 (human blood group O), the resonance spectral width δλ _0.5 is decreased from 26.8 to 25.8 nm for the core mode I and δλ _0.5 is increased from 28.3 to 33.2 nm for the core mode II. In addition, the amplitude sensitivity S _A is increased from 329.7 to 372.2 RIU^?1 for the core mode I and S _A is decreased from 298.2 to 283.7 RIU^?1 for the core mode II. The average value (26.20 nm for core mode I and 31.07 nm for core mode II) of δλ _0.5 from the human blood groups A, B, and O for our plasmonic biosensor is smaller in comparison with a recently published average value (39.10 nm) of the full width at half maximum (FWHM). Our biosensor can be calibrated for a glycerol-water solution by using the linear dependence between the refractive index n _a and the mass fraction w of the solutes.     

On-Chip Oval-Shaped Nanocavity Photonic Crystal Waveguide Biosensor for Detection of Foodborne Pathogens

A photonic crystal waveguide (PCW) biosensor is proposed for the detection of foodborne pathogens. Various semiconductor materials and insulator with higher to lower refractive indices (Si, GaAs, Si₃N₄, and SiO₂) are analyzed to fix the choice of material in PCW design. The design and analysis are performed using finite difference time domain (FDTD) simulation method. The design exhibits two inverted J-shaped defects with center cavity designed in the shape of Escherichia coli. In this research, DH5α strain of E. coli foodborne pathogens is considered as a model due to its shape. Simulation of PCW design is performed using infrared radiation (1 and 1.55 μm) wavelengths. Simulation analysis reports larger resonance wavelength shifts, higher sensitivities, and quality factors for Si-based PCW biosensor at an operating wavelength of 1.55 μm.     

Substrate Temperature Effect on Microstructure,Optical, and Glucose Sensing Characteristics of Pulsed Laser Deposited Silver Nanoparticles

This work reports the substrate temperature-influenced change in the structural, morphological, optical, and glucose sensing properties of silver (Ag) nanoparticles (NPs) deposited on p-type Si (100) wafers. AgNP films grown at temperatures ranging from RT to 600 °C clearly show a dependence of orientation texture and surface morphology on substrate temperature (T _s). As T _s increases from RT towards 600 °C, the preferred orientation of AgNP film changes from (111) to (200). The AgNPs size, that is T _s-dependent, reaches the maximum value at T _s = 300 °C. This result is attributed to restructuring of AgNPs texture. Moreover, the AgNP shape also changes from ellipsoid to sphere as T _s increases from RT to 600 °C. Surface plasmon enhancement in photoluminescence intensity is observed with increase in T _s. It is found also that the AgNP film deposited at 300 °C has considerable reflectance reduction relative to the silicon substrate, in wavelength range of 300–800 nm and a progressive red shift of localized surface plasmon resonances caused by the adding of increasing quantities of glucose has been observed. As a proof of concept, we also demonstrate the capability of grown AgNP substrates for glucose detection based on surface enhanced Raman spectroscopy in physiological concentration range with short integration time 10 s, varying with T _s.     

Molecular Epidemiology of Trypanosomatids and <Emphasis Type="Italic">Trypanosoma cruzi</Emphasis> in Primates from Peru

We determined the prevalence rate and risk of infection of Trypanosoma cruzi and other trypanosomatids in Peruvian non-human primates (NHPs) in the wild (n = 126) and in different captive conditions (n = 183). Blood samples were collected on filter paper, FTA cards, or EDTA tubes and tested using a nested PCR protocol targeting the 24Sα rRNA gene. Main risk factors associated with trypanosomatid and T. cruzi infection were genus and the human–animal context (wild vs captive animals). Wild NHPs had higher prevalence of both trypanosomatids (64.3 vs 27.9%, P < 0.001) and T. cruzi (8.7 vs 3.3%, P = 0.057), compared to captive NHPs, suggesting that parasite transmission in NHPs occurs more actively in the sylvatic cycle. In terms of primate family, Pitheciidae had the highest trypanosomatid prevalence (20/22, 90.9%) and Cebidae had the highest T. cruzi prevalence (15/117, 12.8%). T. cruzi and trypanosomatids are common in Peruvian NHPs and could pose a health risk to human and animals that has not been properly studied.     

Interspecific variation in extracellular polysaccharide content and colony formation of <Emphasis Type="Italic">Microcystis</Emphasis> spp. cultured under different light intensities and temperatures

Single cells of five different Microcystis species (M. ichthyoblabe, M. viridis, M. flos-aquae, M. wesenbergii, and M. aeruginosa) were batch-cultured at different temperatures and light intensities: (a) 25 °C and 50 μmol photons m^?2 s^?1 (control culture); (b) 25 °C and 10 μmol photons m^?2 s^?1; and (c) 15 °C and 50 μmol photons m^?2 s^?1. The extracellular polysaccharide content was significantly higher in treatments b and c than in the control treatment. All Microcystis species existed as single cells under the control treatment but formed colonies in treatments b and c. All of the colonies were irregular with indistinct margins. M. ichthyoblabe, M. viridis, M. flos-aquae, and M. wesenbergii formed colonies with similar morphologies and their cells were loosely aggregated. In contrast, M. aeruginosa formed denser colonies with no distinct holes. The colony morphologies differed from the classic morphology of M. ichthyoblabe field-grown colonies but resembled that of small colonies found in Lake Taihu (Yangtze Delta Plain, China) during early spring. This indicates that field- and laboratory-grown colonies are governed by similar formation processes. We suggest that in laboratory and field environments, M. ichthyoblabe (or M. flos-aquae) colonies are representative of small colonies formed from single Microcystis cells, whereas the morphology of older colonies evolves to resemble M. wesenbergii and M. aeruginosa colonies.     

Polarization Filtering and Phase Controlling Metasurfaces Based on a Metal-Insulator-Metal Grating

Metasurfaces used in the manipulation of light beams have attracted growing interests owing to their unique electromagnetic properties in the subwavelength regime. However, most previously demonstrated single-layer metasurfaces are normally designed to realize one-fold function of either polarization or phase manipulation and suffer from low cross-polarization conversion efficiency and high-background, especially for transmissive metasurfaces. Here, a metasurface based on metal-insulator-metal (MIM) subwavelength grating is proposed to simultaneously achieve polarization filtering and phase controlling. The transmission coefficient reaches up to 78.9% and the polarization extinction ratio (ER = 20*log(T _TM /T _TE) is larger than 16.1 dB. A local abrupt phase difference covering 0–2π is introduced into transmitted light with the polarization direction vertical to the grating by artificially tailoring the geometrical parameters of MIM grating. Furthermore, background-free wavefront control and high-purity radial/azimuthal polarization are realized by the metasurfaces based on the MIM grating. This flexible and high-efficient scheme of full control wavefront and polarization promises an unprecedented progress of spatial vectorial beams modulation and enable the realization of novel optical components.     

Cytotoxicity and Glycan-Binding Profile of a <Emphasis Type="SmallCaps">d</Emphasis>-Galactose-Binding Lectin from the Eggs of a Japanese Sea Hare (<Emphasis Type="Italic">Aplysia kurodai</Emphasis>)

A divalent cation-independent 16 kDa d-galactose binding lectin (AKL-2) was isolated from eggs of sea hare, Aplysia kurodai. The lectin recognized d-galactose and d-galacturonic acid and had a 32 kDa dimer consisting of two disulfide-bonded 16 kDa subunits. Eighteen N-terminus amino acids were identified by Edman degradation, having unique primary structure. Lectin blotting analysis with horseradish peroxidase-conjugated lectins has shown that AKL-2 was a glycoprotein with complex type oligosaccharides with N-acetyl d-glucosamine and mannose at non-reducing terminal. Two protein bands with 38 and 36 kDa in the crude extract of sea hare eggs after purification of the lectin was isolated by AKL-2-conjugated Sepharose column and elution with 0.1 M lactose containing buffer. It suggested that the lectin binds with an endogenous ligand in the eggs. AKL-2 kept extreme stability on haemagglutination activity if it was treated at pH 3 and 70 °C for 1 h. Glycan binding profile of AKL-2 by frontal affinity chromatography technology using 15 pyridylamine labeled oligosaccharides has been appeared that the lectin uniquely recognized globotriose (Galα1-4Galβ1-4Glc; Gb3) in addition to bi-antennary complex type N-linked oligosaccharides with N-acetyllactosamine. Surface plasmon resonance analysis of AKL-2 against a neo-glycoprotein, Gb3-human serum albumin showed the k _ass and k _diss values are 2.4 × 10³ M^?1 s^?1 and 3.8 × 10^?3 s^?1, respectively. AKL-2 appeared cytotoxicity against both Burkitt’s lymphoma Raji cell and erythroleukemia K562. The activity to Raji by the lectin was preferably cancelled by the co-presence of melibiose mimicing Gb3. On the other hand, K562 was cancelled effectively by lactose than melibiose. It elucidated that AKL-2 had cytotoxic ability mediated glycans structure to cultured cells.     

Chemical and molecular identification of the invasive termite <Emphasis Type="Italic">Zootermopsis nevadensis</Emphasis> (Isoptera: Archotermopsidae) in Japan

Numerous termite species have been introduced outside their native ranges by human transport, and some have become invasive. The dampwood termite Zootermopsis nevadensis (Hagen), which is native to western North America, has been introduced to and become established in Kawanishi City, Hyogo Prefecture, Japan. Zootermopsis nevadensis is subdivided into two subspecies based on cuticular hydrocarbon (CHC) phenotypes: Z. nevadensis nevadensis and Z. nevadensis nuttingi (Haverty and Thorne). Here, we identified Z. nevadensis in Japan as hybrids between the two subspecies. Chemical analysis showed the presence of 7,15-dimethylhenicosane and 5,17-dimethylhenicosane in the CHCs of Z. nevadensis in Japan, corresponding to the CHC phenotype of Z. n. nevadensis. Conversely, all mitochondrial cytochrome c oxidase subunit I sequences of Z. nevadensis in Japan were identical to sequences from Z. n. nuttingi and hybrids between the two subspecies from a native hybrid zone in California, USA. In addition, phylogenetic analysis showed that Z. nevadensis in Japan formed a clade with Z. n. nuttingi and hybrids between the two subspecies. Our results show discordance between the chemical and genetic features of Z. nevadensis in Japan, indicating that individuals of Z. nevadensis in Japan are hybrids between the two subspecies.