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• Symmetrical polishing structure of dual-core photonic crystal fiber. • Gold layer is plated on the symmetrical side-polished surface of PCF to excite the surface plasmon polaritons. • The proposed sensor is able to detect the analyte the refractive indexes in the range of 1.3–1.42. • The maximum sensitivity of the proposed sensor is 8000 nm/RIU. A surface plasmon resonance (SPR) sensor based on symmetrical side-polished dual-core photonic crystal fiber (DC-PCF) with a wide refractive index (RI) detection is proposed and analyzed. A gold layer is placed on the symmetrical side-polished surface of photonic crystal fiber to excite the surface plasmon polaritons (SPPs). The proposed DC-PCF consists of the symmetrical air-holes and symmetrical side-polished structure. The design without air holes on both sides of the core can efficiently realize phase matching between the core guided mode and the plasma mode. Numerical simulation results show a maximum sensitivity as high as 8000 nm/RIU (refractive index unit) with a resolution of 1.3 × 10−5 RIU. It has a significant advantage in the field of chemical and biological detection because it is able to detect the analyte RI in the range of 1.3–1.42. [ABSTRACT FROM AUTHOR]

Highlight • A high-sensitivity PCF sensor was designed for analyte detection. • This optimized sensor had an excellent linearity and good sensitivity. • The sensitivity within the refractive index range of 1.425–1.45 is 60,611 nm/RIU. • The corresponding minimum detection limit is 1.58 × 10−6 RIU. • The sensitivity within the refractive index range of 1.45–1.46 is 28,000 nm/RIU. • The corresponding minimum detection limit is 2.86 × 10−6 RIU. Abstract A high-sensitivity photonic crystal fiber (PCF) refractive index sensor based on the resonant coupling of core mode and defect mode is studied by the finite element method. The large liquid-filled is placed near to the core for easy coupling with the core mode. The simulation results show that when the refractive index of the analyte is 1.425–1.45 and 1.45–1.46, the average sensitivity is 60,611 and 28,000 nm/RIU respectively, and the corresponding minimum detection limits are 1.58 × 10−6 and 2.86 × 10−6 RIU. [ABSTRACT FROM AUTHOR]

A high sensitivity photonic crystal fiber (PCF) temperature sensor based on surface plasmon resonance is proposed and evaluated using the finite element method. Besides, the coupling phenomenon is studied. The gold layer deposited on the polishing surface of D-shape PCF is used as the metal to stimulate surface plasma, which can improves the sensitivity. Through exquisite design, the birefringence of the fiber is improved, which makes the loss of y-polarization far greater than the loss of x-polarization. The D-shape fiber avoids filling metal and liquid into the air-holes, which can contact with fluid directly to feel temperature. When the phase matching condition is satisfied, the core mode will couple with the surface plasma mode. The resonance position of y-polarization is very sensitive to the temperature change. The simulation shows that the PCF has high sensitivity of 36.86 nm/°C in y-polarization and wide detection that from 10 °C to 85 °C. [ABSTRACT FROM AUTHOR]

A groove micro-structure optical fiber refractive index sensor with nanoscale gold film based on surface plasmon resonance (SPR) is proposed and analyzed by the finite element method (FEM). Numerical results show that the average sensitivity is 15,933 nm/refractive index unit (RIU) with the refractive index of analyte ranging from 1.40 to 1.43 and the maximum sensitivity is 28,600 nm/RIU and the resolution of the sensor is 3.50 × 10 −8 RIU. The groove micro-structure optical fiber refractive index sensor do some changes on the D-shaped fiber sensor, compared with conventional D-shaped fiber sensor, it has a higher sensitivity and it is easier to produce than the traditional SPR sensor. [ABSTRACT FROM AUTHOR]

A polarization filter is designed at two communication windows of 1310 and 1550 nm based on microstructured optical fiber. The model has four large diameter air holes and two gold-coated air holes. The influence of the geometrical parameters of the photonic crystal fiber on the performance of the polarization filter is analyzed by the finite element method. The numerical simulation shows that when the fiber length is 300 μm, the corresponding extinction ratio is 209.7 dB and 179.8 dB, the bandwidth of extinction ratio (ER) better than 20 dB is 150 nm and 350 nm at the communication wavelength of 1310 nm and 1550 nm. [ABSTRACT FROM AUTHOR]

• We propose a novel superposition-assisted structure (SAS) in few-mode multi-core fibers (FM-MCFs) to effectively suppress inter-core crosstalk (XT). • The designed SAS fiber can realize low XT characteristic while keeping good fiber transmission performances such as effective mold field area, dispersion, differential mode group delay and bending loss. • The optimal SAS FM-MCF achieve the XT below −50 dB/100 km at a cladding diameter of 125 μm, which is conducive to the docking with the existing optical fiber technology. • The designed SAS is suitable for the application of low-XT and large-capacity FM-MCFs based on space division multiplexing (SDM) technology. We propose a novel superposition-assisted structure (SAS), composed of trench and air holes, in few-mode multi-core fibers (FM-MCFs) to effectively suppress the inter-core crosstalk (XT). The proposed SAS can minimize the inter-core XT to −70.58 dB/100 km in the 7-core fibers, which is 60 dB/100 km lower than the typical trench-assisted structure and 29 dB/100 km lower than the typical hole-assisted structure, respectively. In addition, the SAS does not introduce extra fiber loss and dispersion. In this paper, the key properties of SAS MCFs are numerically simulated using the finite element method (FEM). The large effective area (A eff) over 90 μm2 enables the suppression of nonlinear effects. The values of dispersion coefficient and differential mode group delay (DMGD) are in the range of 24–42 [ps/(nm·km)] and 5–23 ps/m over C + L band, respectively, which are favorable for fiber communication systems. Such SAS 7-core 5-LP-mode fibers can be further optimized to obtain the cladding diameter of 125 μm, where five propagation modes achieve inter-core XT target below −50 dB/100 km with the bending radius less than 500 mm. Besides, the optimized relative core multiplicity factor (RCMF) can be up to 97.55. The proposed SAS provides a promising solution for the design of FM-MCFs with ultra-low inter-core XT and high capacity for space division multiplexing (SDM). [ABSTRACT FROM AUTHOR]

Abstract: Oligochitosan has been shown to induce several plant defense responses. In the present work, the effect of oligochitosan on tobacco cell survival was investigated. The results showed that oligochitosan caused tobacco cell death in a dose-dependent manner. About 40.6 % tobacco cells died when cultured for 72h after 500μgml−1 oligochitosan treatment. Certain aspects of this cell death process appeared to be similar to apoptosis in animal cells. These included shrinkage of cytoplasm and condensation of chromatin. Oligochitosan also induced H2O2 accumulation in tobacco cell suspension culture. The role of H2O2 in the signal transduction that leads to cell death was investigated. Co-treatment of tobacco cells with oligochitosan and catalase inhibited H2O2 accumulation but did not inhibit the induction of cell death. The results suggested that apoptosis-like cell death of tobacco cells induced by oligochitosan is independent of H2O2 signal pathway. [Copyright &y& Elsevier]

• The sensor is capable of detecting a refractive index change of the liquid analyte ranging from 1.33 to 1.38. • The gold film and the thin layer of graphene are directly coated on the outer edge of the fiber. • After adding graphene, the average sensitivity increases from 2938.86 to 5171.51 nm/RIU. • The maximum sensitivity can reach 8600 nm/RIU. • The optical fiber can be directly immersed into the liquid analyte, so real-time detection can be realized. A novel eccentric photonic crystal fiber biosensor with gold and graphene bimetallic layers on the outer edge of the optical fiber is proposed in this paper. The effects of gold film thickness, graphene coating thickness and cladding air hole diameter on the sensor performance are analyzed in detail. The maximum sensitivity of this PCF sensor is 4657.14 nm/RIU when only gold-plated film is used, and 8600 nm/RIU after a layer of graphene is added on the gold film, the sensitivity increased by 84.66%. Compared with the traditional optical fiber sensor, this PCF sensor has the advantages of simple structure, easy manufacture and real-time detection, which will make it a potential candidate for water quality analysis, chemical detection and biomolecular detection. [ABSTRACT FROM AUTHOR]

• The sensor is capable of detecting a refractive index change of the liquid analyte ranging from 1.33 to 1.41. • The sensitivity of the sensor can reach a maximum of 22071 nm/RIU when the refractive index of liquid analyte is 1.41. • The performance of the sensor can be improved by optimizing its structural parameters. • It can easily be implemented for the manufacture of the proposed fiber sensor in actual production. A novel high-sensitivity circular dual-core photonic crystal fiber refractive index sensor is proposed in this paper. The effects of air hole spacing, liquid filled air hole diameter and cladding air hole diameter on its sensor sensitivity are analyzed in detail. The simulation results show that the liquid refractive index that the sensor can detect ranges from 1.33 to 1.41. By optimizing the geometric parameters, when the analyte refractive index is 1.33 and 1.41, respectively, the minimum sensitivity of this PCF sensor is 8929 nm/RIU, and the maximum value can reach 22071 nm/RIU. Due to its high sensitivity and simple structure, this PCF sensor can be widely used for chemical detection and biomolecule detection. [ABSTRACT FROM AUTHOR]

Highlights • The proposed PCF structure is a combination of circular layout and D-shaped. • The gold film is deposited on the polishing surface, the analyte is placed on the outer layer of the D-shaped PCF. • The proposed PCF sensor is feasible for the structural parameters with fabrication tolerance of ±1%. • The proposed sensor easy to fabricate and has high sensitivity. Abstract A high sensitivity D-shaped photonic crystal fiber sensor based on surface plasmon resonance is proposed for refractive index sensing. By using finite element method, the sensing properties of the proposed sensor are investigated. The numerical results show a very high average sensitivity of 14600 nm/RIU with the high resolution of 6.80 × 10−6 RIU for refractive index (RI) of analytes ranging from 1.420 to 1.435. The layout of the air holes is designed to be circular and only two layers in this D-shaped photonic crystal fiber. The metallic gold is used as the surface plasmon resonance activity material, which is deposited on the polishing surface. The analyte is placed on the outer layer of the D-shaped photonic crystal fiber. This D-shaped photonic crystal fiber solves the difficulty of gold-plated film and fill analyte in the holes. The proposed PCF structure is a combination of circular layout and D-shaped, which also leads to the proposed sensor easy to fabricate and has considerable sensitivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diflufenican solubility in three cosolvent mixtures were determined and correlated. • Inter-molecular interactions of diflufenican-solvent were studied. • Solubility behavior was studied through EHSA model. • Preferential solvation were investigated via inverse Kirkwood–Buff integrals method. • Dissolution properties as well as enthalpy–entropy compensation were studied. Electrostatic characteristics of acidity and basicity of the diflufenican molecule were uncovered by examining the Hirshfeld surface and the electrostatic potential surface, respectively. When it comes to nucleophilic and electrophilic assault, the >NH, =O, and -O- groups are where it is at. Diflufenican-solvent interactions were shown using an independent gradient model based on Hirshfeld partition analysis. Under 101.2 kPa, the isothermal saturation technique was used to experimentally obtain the diflufenican solubility in mixtures of isopropanol/methanol + water and ethyl acetate + ethanol across the temperature range from 278.15 to 323.15 K. Diflufenican was more soluble in ethyl acetate + ethanol blends than alcohol + water blends at the same temperature and cosolvent composition. Maximum relative average deviation of 9.57 percent was obtained using the Jouyban-Acree and modified van't Hoff-Jouyban-Acree models of correlation. The literature-reported solubility of diflufenican in ethylene glycol (EG), ethanol, propylene glycol (PG), and N , N -dimethylformamide (DMF) + water, as well as our determined in ethyl acetate + ethanol and methanol/isopropanol + water at 298.15 K, were all investigated using an extended Hildebrand solubility parameter approach. The local mole fractions of diflufenican in the seven solutions were also investigated using the inverse Kirkwood-Buff integrals technique. Preferential solvation of diflufenican by PG, ethanol, DMF, methanol, and isopropanol in aqueous solutions and by ethyl acetate in ethyl acetate + ethanol solutions was observed. Diflufenican in aqueous EG mixes was not preferentially solvated by EG. Results and discussion of the enthalpy–entropy compensation features of dissolution were reached. [ABSTRACT FROM AUTHOR]

Highlights • The PCF is simple, novel and easy to apply. • The filter can simultaneously achieve polarization filtering effects on the input signals of the 1310 and 1550 nm communication bands. • When the length of the PCF is 0.8 mm, the crosstalk is less than −20 dB or better than 20 dB in the 1550 and 1310 nm bands, the optical bandwidth can reach 220 and 150 nm, respectively. Abstract A photonic crystal fiber (PCF) polarization filter with dual communication bands is proposed in this paper. The polarization characteristics of the double-hole gold-coated PCF are numerically analyzed by utilizing the finite element method (FEM). As we know, the filter can achieve polarization filtering effect on input signals at 1310 nm (y-polarized mode) and 1550 nm (x-polarized mode) bands simultaneously in two orthogonal polarization states. In the above two communication bands, the confinement losses of the unwanted polarization mode can reach 192.7 dB/cm (y-polarized mode) and 427.5 dB/cm (x-polarized mode), whereas other polarization mode losses are very low. Furthermore, when the transmission length of the PCF is 800 μm, x and y polarization mode crosstalk can reach −275.4 and 126.9 dB in the 1550 and 1310 nm bands, respectively. Meanwhile, the crosstalk is less than −20 dB or better than 20 dB, the optical bandwidth can reach 220 and 150 nm, respectively. [ABSTRACT FROM AUTHOR]

Abstract A magnetic field sensor based on magnetic fluids (MFs) selectively infilling photonic crystal fiber (PCF) is designed and analyzed by the finite-element method (FEM). The PCF consists of three-layer air holes in the cladding which are arranged in regular hexagonal lattice. The left and right sides of the fiber core are made up of two larger circular air holes while the upper and below sides are made up of four smaller circular air holes which are benefit to enhance the birefringent effect. MFs are injected into one air hole in the second cladding layer which generates a defect core with high confinement loss. Air holes around the defect core are asymmetrically distributed which can enhance the birefringence of the transmission mode in defect core. When the phase matching condition between core modes and defect core modes is satisfied, the light transmitting in the core couples to the defect core and a sharp decrease of light transmitting energy occurs. The refractive index of defect core modes is modulated by magnetic field strength. The peak wavelengths of confinement loss spectra depicts pretty well linear relationship with magnetic field strength in the detected range of 30–130 Oe. The magnetic field measuring sensitivity reaches to 584 pm/Oe for x-polarized mode and 700 pm/Oe for y-polarized mode, respectively. [ABSTRACT FROM AUTHOR]

A high sensitivity optical fiber Surface Plasmon Resonance (SPR) sensor which based on coreless optical fiber, silver film and graphene, has been designed and implemented for liquid concentration detection. In this paper, Graphene is firstly verified that it can be used to enhance the evanescent field of traditional optical fiber and thus increasing sensitivity in experiment. The sensitivity of proposed sensor is 6.417 nm/%, which is higher than that of the traditional optical fiber SPR sensor according to the comparative experiments. In addition, the proposed sensor is extremely easy to make and the silver film could be protected from oxidation and damage due to the existence of graphene. Moreover, the sensor has pretty small size, immunity to electromagnetic interference, quick response speed and thus can suitable a variety of severe environments and real-time measurement. [ABSTRACT FROM AUTHOR]

• A magnetic field measurement sensor based on Faraday rotation effect in TLWMN glass tellurite fiber is theoretically proposed. • Compared with traditional silica fibers, TLWMN no-core-fiber has a higher Verdet constant, which makes contributions to improving the sensitivity. • It is an all-fiber structure where the fiber works both as the medium for light transmission and magnetic sensing. In this work, a magnetic field measurement sensor based on Faraday rotation effect in TeO 2 -Li 2 O-WO 3 -MoO 3 -Nb 2 O 5 no-core fiber (TLWMN NCF) is theoretically proposed. Compared with traditional silica fibers, TLWMN NCF has a higher Verdet constant, which makes contributions to improving the sensitivity. Comparative analysis concerning the Verdet constant and sensitivity of the designed sensor and its silica counterpart at different wavelength is presented, where the highest sensitivity of TLWMN NCF at measuring a uniform magnetic field can reach 2.2 × 10−3 rad/Gs at the wavelength of 442 nm, and the value decreases slightly when measuring a non-uniform magnetic field, which is 1.91 × 10−3 rad/Gs. The superior sensitivity and independence of other magnetic sensitive materials attribute the designed sensor an appropriate candidate in terms of magnetic field measurement in numerous fields. [ABSTRACT FROM AUTHOR]