Search

A D-shaped photonic crystal fibre filled with liquid crystal was demonstrated as an amphibious sensor for detection of both temperature and refractive index, when combined with plasma materials. Specifically, the optical component is implanted into a complete optical system ensuring modulation of the external electric field. When the refractive index of the external solution changes from 1.0 to 1.6, the y-polarised mode has a loss spectrum with a wavelength sensitivity of up to 2275 nm/RIU, and the corresponding amplitude sensitivity is −88.2RIU−1. When the perceived temperature changes from 15°C to 50°C, the temperature of the sensor is correspondingly expressed as the maximum wavelength sensitivity of 9.09 nm/°C and the amplitude sensitivity of −0.311°C−1. In addition, the actual micro-operation processes have been studied in detail, such as polishing depth, coating thickness and coating method. This provides practical ideas for real-time sensing analysis that requires harsh environments. [ABSTRACT FROM AUTHOR]

G-series nerve agents, such as sarin, tabun, and soman, would cause tremendous harm in military and terrorist attacks, so it is necessary to develop a simple method for the rapid and efficient detection of these hazardous substances. We have developed a tunable acetylcholinesterase (AChE)-functionalized two-dimensional photonic crystal (2D PhC) for the detection of a real nerve agent, sarin. In accordance with the 2D PhC previously prepared by our group, the AChE-functionalized 2D PhC was optimized by adjustment of the amount of monomer in the hydrogel, which not only increased the sensitivity of the 2D PhC, with the detection limit decreasing by two orders of magnitude, but also ensured the structural color spanned the whole visible region in the detection range. A linear relationship between the logarithm of the sarin concentration and the particle spacing of the AChE-functionalized 2D PhC was observed from 7.1 × 10-17 to 7.1 × 10-4 mol/L. The AChE-functionalized 2D PhC also responded to mimics of G-series nerve agents, including dimethyl methylphosphonate, diisopropyl methylphosphonate, and isodipropyl methylphosphonate, to various degrees. The proposed 2D-PhC hydrogel has potential for low-cost, trace-level, and on-site monitoring of other G-series nerve agents. Graphical abstract [ABSTRACT FROM AUTHOR]

A dual communication band single-polarization photonic crystal fibre polarizing filter based on surface plasmon resonance is presented in this paper. Numerical simulation results demonstrate that the resonance strength of x- and y-polarized direction can reach 569.83 and 719.25 dB.cm−1 simultaneously at the communication wavelength of 1.31 and 1.55 µm. By filling liquid analyte, the confinement loss of x- and y-polarized direction can simultaneously reach 831.7 and 580.53 dB.cm−1 at the wavelength of 1.31 and 1.55 µm. Furthermore, when the fibre length L is equal to 700 µm, the peak value of the crosstalk can reach 493.86 and −323.67 dB at the same time at the wavelength of 1.31 and 1.55 µm, and when the length of the fibre L is 400 µm, the bandwidths of the crosstalk better than 20 dB and less than −20 dB are about 160 and 210 nm, respectively. These performances make it an ideal candidate for designing dual-band polarization filter equipment. [ABSTRACT FROM AUTHOR]

A compact glucose sensor is proposed by using a short length of photonic crystal fiber inserted in a Sagnac loop interferometer. Spectrum shift in response to the RI of glucose solution with a high average sensitivity of 22 130 nm/RIU is achieved, equivalent to 0.76 mg/dL of glucose in water, which is lower than 70 mg/dL for efficient detection of hypoglycemia episodes. And the simplicity of the fiber structure makes the sensor production very cost effective. We aimed to provide a potential effective method for glucose detection in patients with hypoglycemia. [ABSTRACT FROM AUTHOR]

A kind of multi channel dual-core photonic crystal fiber polarization beam splitter is designed. We analyze the effects of the lattice parameters and the thickness of gold layer on the beam splitting by the finite element method. Numerical results show that the thickness of metal layer and the size of the air holes near the fiber cores are closely linked with the nature of the polarization beam splitter. We also obtain that extinction ratio can reach −73.87 dB at 1 . 55 μ m wavelength and at 1 . 41 μ m, 1 . 65 μ m extinction ratio can reach 30.8978 dB and 31.1741 dB, respectively. The comparison of the effect on the characteristic of the photonic crystal fiber with coating no gold is also taken into account. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We propose and investigate a photonic crystal fiber (PCF) refractive index sensor with triangular lattice and four large-size channels based on surface plasmon resonance. In such sensor, two gold wires obtained by chemical reaction are filled in two air holes between the upper and lower channels. Numerical results show that the refractive indexes of the analytes can be detected from 1.30 to 1.79. It's a very broad detection range that is rarely seen in the field of photonic crystal fiber sensor based on surface plasmon resonance. The average sensitivity of this photonic crystal fiber could be 100 nm/refractive index unit (RIU) in the dynamic index range from 1.30 to 1.63. In the range from 1.63 to 1.79, the highest sensitivity could reach to 3233 nm/RIU. The ability to integrate four large-size microfluidic channels for efficient analyte flow in is attractive for the development of integrated highly sensitive PCF-SPR sensors. [ABSTRACT FROM AUTHOR]

A kind of photonic crystal fibre polarization filter with round lattice based on surface plasmon resonance is proposed. Complete coupling happens between core mode and second-order surface plasmon polariton (SPP) mode when the phase-matching condition is satisfied. We can adjust the resonance point and strength in two polarizations by changing the fibre birefringence and the thickness of gold film. Numerical simulation with the finite-element method shows that the resonance strength can reach 364.8 dB/cm in they-polarized direction at the communication wavelength of 1550 nm, when the diameter of big air holes that lead to the birefringence is 2.0 m and the thickness of gold film is 26 nm. Moreover, when the fibre length is 800 m, the peak value of the crosstalk can reach 231.8 dB and the bandwidth of the crosstalk better than 20 dB can reach 130 nm. This makes it a promising candidate for polarization filter devices. [ABSTRACT FROM PUBLISHER]

In this paper, two kinds of novel plasmonic polarization beam splitters based on dual-core photonic crystal fiber (DC-PCF) have been designed and analyzed through the full-vector finite element method. The metallic gold is used as the surface plasmon resonance (SPR) active metal. The coupling characteristics of the designed DC-PCF can be enhanced by the resonant coupling between the second-order surface plasmon polariton (SPP) mode and the core-guided modes. A gold layer in the designed DC-PCF is introduced to achieve an perfect splitting performance and an ultra-bandwidth compared to the designed DC-PCF with gold wire. Numerical results show the ultra-bandwidth of core A and B of the polarization beam splitter with gold layer can reach 210 and 220 nm, as the extinction ratio better than -20 dB, covering the E, S, C, and L optical communication bands. The extinction ratios of core A and B can reach to -84 and -46 dB at the wavelength of 1.55 μm, respectively, and the length of splitter is 0.542 mm. [ABSTRACT FROM AUTHOR]

An ultrabroad bandwidth polarization filter based on D-shaped photonic crystal fibers with gold film is proposed. The design of gold film deposited on the polished plane of the D-shaped photonic crystal fibers is benefit to generate multiple resonances between surface plasmon polaritons and photons. In our designed polarization filter, the resonant intensity in y-polarization direction is much stronger than in x-polarization direction. An ultrabroad bandwidth of exceeding 1 μm with extinction ratio better than -20 dB is obtained. The performance characteristics of the filter can be improved further by optimizing the structure parameters of the D-shaped photonic crystal fibers. [ABSTRACT FROM AUTHOR]

A broadband single-polarization photonic crystal fiber polarized filter based on surface plasmon resonance is proposed based on finite element method. Numerical simulations show the confinement loss of y-PCM (y-polarized core mode) is much higher than that of x-PCM (x-polarized core mode) in the wavelength range 1.20-1.63 μm. The confinement loss of y-polarized mode is 45,240 and 10,200 dB/m at the communication wavelength 1.31 and 1.55 um, respectively, and the corresponding loss of x-polarized mode is just 90 and 80 dB/m. When the fiber length is 3 mm, the bandwidth of extinction ratio better than -20 dB is greater than 430 nm covering almost all the communication wavelength. To our best knowledge, the bandwidth is the widest. The impacts of structural parameters on the resonance characteristics are also discussed. The structure could be further optimized for better result. [ABSTRACT FROM AUTHOR]

A kind of elliptical structure photonic crystal fiber with diameter increasing air holes is proposed. In this structure all the circular air holes are arranged in six elliptical rings. And the diameter of each rings increase from the inner to the outer. Moreover, we have choose some air holes to coating the metal Au and filling the liquid of the purified water. Properties, just like the confinement loss, of these structures with different diameters of the holes and thickness of the gold layer are numerical analyzed by using the finite element method. Numerical results show that the resonance strength in x-direction is much stronger than in y-polarized direction, and filling the liquid and changing the thickness of the gold film can significantly increase the loss of core mode polarized in the x-polarized direction. [ABSTRACT FROM AUTHOR]

Magnetic field sensor based on magnetic fluid selectively infilling photonic crystal fibers is designed and analyzed by the finite-element method. One cladding air hole is infiltrated with magnetic fluid and works as a defect core. As the phase matched condition is satisfied, the lights in transferring core couple to the defect core and the confinement losses of core modes experience an abrupt increase. The sensitivity and figure of merit can reach to 456.1 pm/Oe, 0.408 Oe−1 for $x$ -polarized direction and 542.9 pm/Oe, 0.169 Oe−1 for $y$ -polarized direction, respectively. The designed magnetic fluid selectively infilling photonic crystal fibers which show small volume, high sensitivity, and figure of merit are suitable for magnetic field sensor. [ABSTRACT FROM PUBLISHER]

In this paper we propose a gold-plated photonic crystal fiber (PCF) refractive index sensor based on surface plasmon resonance (SPR), in which gold is coated on the external surface of PCF for easy fabrication and practical detection. The finite element method (FEM) is used for the performance analysis, and the numerical results show that the thickness of the gold film, the refractive index of the analyte, the radius of the air hole in the first layer, the second layer, and the central air hole can affect the sensing properties of the sensor. By optimizing the sensor structure, the maximum wavelength sensitivity can reach 11000 nm/RIU and the maximum amplitude sensitivity can reach 641 RIU−1. Due to its high sensitivity, the proposed sensor can be used for practical biological and chemical sensing. [ABSTRACT FROM AUTHOR]

A high-sensitivity temperature sensor based on photonic crystal fiber Sagnac interferometer is proposed and studied. All holes of the PCF are filled with ethanol with capillarity. The cladding air holes are uniform arrangements. The two air holes around the core are removed to form new core modes with high birefringence. The sensitivities of the temperature can be up to −8.7657 and 16.8142 nm/∘C when temperature rises from 45 to 75 ∘C and the fiber length is 5.05 cm. And when temperature rises from 10 to 45 ∘C, the sensitivity can reach −7.848 and 16.655 nm/∘C with fiber length 2.11 cm. The performance of the selective-filled and the fully-filled PCF with temperature from 45 to 75 ∘C and fiber length 5.05 cm are analyzed and compared. The fully filling can better achieve PCF’s sensing performance. The simple structure and high sensitivities make the temperature sensor easy to achieve. The temperature sensor with high sensitivities and good linearity has great application value for environmental temperature detecting. [ABSTRACT FROM AUTHOR]

In this paper, a photonic crystal fiber with the gold layer is simulated by finite element method. Due to birefringence, surface plasmon resonance only occurs in the y-polarization direction. The loss of y-polarization mode is much larger than that of x-polarization mode. The photonic crystal fiber is suitable for the polarization filter. The polarization filter has the short length and high extinction ratio. Furthermore, the insertion loss of the x-polarization mode is only 0.07 dB, which is the smallest as far as we know. [ABSTRACT FROM AUTHOR]

The indiscriminate use of nerve agents by terrorist groups has attracted attention of the scientific communities toward the development of novel sensor technique for these deadly chemicals. A photonic crystal (PhC) hydrogel immobilized with butyrylcholinesterase (BuChE) was firstly prepared for the sensing of Sarin agents. Periodic polystyrene colloidal (240 nm) array was embedded inside an acrylamide hydrogel, and then BuChE was immobilized inside the hydrogel matrix via condensation with 3-(diethoxyphosphoryloxy)−1,2,3-benzotriazin-4(3 h)-one (DEPBT). It indicated that a total of 3.7 units of BuChE were immobilized onto the PhC hydrogel. The functionalized hydrogel recognized the Sarin agent and then shrunk, thus the diffraction of PhC hydrogel blue shifted significantly, and a limit of detection (LOD) of 10 −15 mol L −1 was achieved. [ABSTRACT FROM AUTHOR]

Photonic crystal fiber-based polarization filter has important application prospects in optical fiber communications, nonlinear optics, and sensors. In order to achieve polarization filters with optimal performance, some numerical methods have been used to search for optimal results under different geometric structure parameters of fibers. However, it is unrealistic to calculate solutions under every parameter. In addition, the search direction and scope of adjusting fiber geometric structure parameters still depend on the designer's intuition and experience. Therefore, we propose a novel design method for photonic crystal fiber polarization filters to overcome these questions. The optimization design problem of polarization filters is transformed into the single objective function optimization problem. The combination of artificial neural networks and intelligent optimization algorithms realizes the optimal value-solving problem in two-dimensional parameter space. The method efficiently and automatically searches for optimal structures in the parameter space by fine-tuning both variables simultaneously, improving the bandwidth of the polarization filter and achieving higher crosstalk at 1550 nm. The method eliminates computationally expensive wavelength parameters and greatly reduces computation time. This novel design method realizes the reverse design of photonic crystal fiber-based polarization filters. In addition, the new method can also be used to design polarization filters at other objective wavelengths, and it is potentially applicable to the design of other photonic crystal fiber devices. • Wavelength parameters are removed, drastically cutting down on computation time. • The polarization filters optimization design is transformed into function optimization. • Machine learning techniques provided optimal design parameters of polarization filters. [ABSTRACT FROM AUTHOR]

Compared with traditional optical fiber, photonic crystal fiber (PCF) has many novel optical properties owing to its diversity in cladding distribution. But, it is a problem to measure the optical properties of PCF under variable structural parameters. Artificial neural networks (ANNs) have been used to predict the optical properties of PCF, but ANNs have the multiple local minima problems, whereas support vector machines' solutions are globally unique and will not fall into local minimum values. In this paper, support vector machines (SVMs) based on radial basis functions were used to predict the effective refractive index (n e f f), chromatic dispersion (D), and confinement loss (α c) of PCF. Well-trained SVMs can accurately and quickly predict the optical properties of any geometric parameters in the studied parameter space. A data set similar to Gaussian distribution was formed by two logarithmic transformation methods to avoid the problem that machine learning models cannot be well trained on extremely skewed distribution. Compared to ANNs, SVMs are more accurate and show stable prediction results. [ABSTRACT FROM AUTHOR]

Abstract: A kind of sandwich structure photonic crystal fiber with diameter-increasing air holes is proposed. The sandwich structure is composed of the rectangular lattice in the center and triangular lattice in both sides, which is used to gain high birefringence. The air holes in the cladding, whose diameter in outer ring is always larger than the next inner ring, is used to reduce the confinement loss. The model field, dispersion, birefringence and confinement loss of the fiber fundamental mode are simulated by full-vector finite element method. It was shown from numerical results that it is possible to design a PCF with birefringence B =3.8×10−3 and the fast axis confinement loss less than 10−3 dB/km at wavelength of 1550nm. [Copyright &y& Elsevier]

Abstract: Cladding-ring-equivalent effective index method (CREEIM) is proposed to analyze the propagation characteristics in the multi-cladding photonic crystal fibers (MCPCFs). The effective indices and dispersions of the step index two and three-cladding structures are calculated with the Sellmeier formula. The accuracy of CREEIM is competitive to the results calculated by the multipole method (MPM). With different structure parameters, the differences between two methods are evaluated with the relative error R E of effective index and relative difference R D of dispersion. This method is also used to analyze the mode cut-off and nonlinear characteristics in the three-cladding structure PCFs by calculating the mode effective index n eff instead of complex mode field distribution. [Copyright &y& Elsevier]