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In this paper, slow light features of an engineered photonic crystal waveguide are presented. The combined effect of lattice shift, lattice twist and introduction of ring-like holes (rings) in the innermost rows on the slow light features is studied. The rings are introduced in the first and second innermost rows of the waveguide. Slow light is characterized by calculating group index, second and fourth-order dispersions, and delay-bandwidth products. MIT Photonic Bands software is used for simulation. With rings in the innermost rows, a flat band of 17.71 nm is observed with a group index value of 12.72 and a flat band of 40.16 nm with a group index of 7.77. The normalized delay bandwidth product (NDBP) is observed as 0.1378 in the first structure and 0.1874 in the second structure with the proposed effects. These values are nearly 4.3 times higher in comparison with the NDBP value of the base structure (0.0436) and approximately 2 times higher than the engineered structure (0.0927). These structures are useful in slow light applications. [ABSTRACT FROM AUTHOR]

Theoretically, we aim to optimize the parameters related to slow light in a 2D heterostructure photonic crystal. Two types of heterostructures were investigated by joining two photonic crystals: one composed of square holes and the other with circular rods or vice versa. The plane wave expansion and supercell method are used to analyze the waveguide mode. Germanium is assumed to be the material for the rods and background. The group index and bandwidth for the waveguide appearing at the interface were optimized. A comprehensive survey of rod and hole size values reveals that the achieved group index bandwidth product of 0.72 is primarily due to the high bandwidth achieved within the optimized structure. Furthermore, our results confirm that rotating the square rods can further enhance slow light parameters, leading to a significantly higher group-index-bandwidth product than traditional semiconductor photonic crystal waveguides. [ABSTRACT FROM AUTHOR]

Miniaturized and head-mountable scanning nonlinear fibre-optic microscopy offers an exciting opportunity for the visualization of brain activity on freely walking mice. One challenge in the creation of such miniaturized microscopes is the design of optical fibres capable of delivering ultrashort pulses without distortion and collecting fluorescence simultaneously and efficiently. A double-clad photonic crystal fibre (DCPCF) with 37-cell air holes arranged in hexagonal lattice in core is proposed. The full vector finite element method (FEM) is used for numerical analysis. Nearly zero dispersion of −0.34 ps/nm/km at 920 nm wavelength is finally achieved. The single-mode core with an NA of 0.53 at 920 nm wavelength is used to deliver the femtosecond excitation beam and the inner cladding with an NA of 0.54 at 532 nm is used to collect the two-photon fluorescence signal. The nearly zero dispersion, high NA and low nonlinearity will be beneficial to promote its application in two-photon microscopy. [ABSTRACT FROM AUTHOR]

A proposal is made in this paper to realize 3-ways chip to chip communication via 3D photonic structure. The mechanism of the work is understood with the help of absorbance and reflectance of the structure. The absorbance is determined using the analytical treatment where reflectance is computed using the photonic bandgap analysis, which is found with the help of plane wave expansion method. Further the present research deals with low power input signal whose potential varies from 0.55 to 1 V because to avoid the heat generation in nanoelectronics and nanophotonic circuits where circuit comprises chip, LED and photo detector along with waveguide (3D photonic structure). The output results indicate that a proper combination of lattice spacing of silicon-based 3D photonic structure and diameter of air holes could be a right candidate to realise 3-ways communication. [ABSTRACT FROM AUTHOR]

A relative humidity (RH) sensor is reported based upon a photonic crystal fiber (PCF) – Mach-Zehnder interferometer (MZI) with a polyvinyl alcohol (PVA) coating. The structure for sensing was prepared by fusing photonic crystal fiber to two single-mode fibers (SMFs) and completely collapsing the air holes of photonic crystal fiber in the fusion area to act as the beam splitter and coupler. By a lifting method, two to four layers of polyvinyl alcohol films were coated upon the photonic crystal fiber to characterize the influence of its thickness upon the sensitivity of the device for relative humidity. The experimental results show that the maximum sensitivity of this relative humidity sensor is 51.9 pm/% when the photonic crystal fiber surface is coated with three layers of polyvinyl alcohol film. [ABSTRACT FROM AUTHOR]

A surface-modified D-type photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) is reported for application as a polarization filter and refractive index sensor. The gold film is deposited on the surface of the designed fiber structure to stimulate the SPR effect. Through etching, the upper surface of the designed structure forms an angle of 170°. The etching angle changes the distance between the fiber core and the surface of gold film to enhance the local field SPR effect. The designed optical device is numerically simulated using the finite element method (FEM), the mode distribution is studied, and the coupling phenomenon is analyzed. At a wavelength of 1.31 µm, the y-polarization loss is 1307.90 dB/cm, while the loss of x-polarization is 1.13 dB/cm; at 1.55 µm, the y-polarization loss is 1755.19 dB/cm, while the x-polarization loss is only 1.24 dB/cm. In the case of the same structure parameters as the proposed polarization filter, of which communication window is 1.55 µm, the designed structure also serves as a refractive index sensor from 1.330 to 1.365. The average sensitivity of the refractive index sensor is up to 4857 nm/RIU, and the highest sensitivity is 7588 nm/RIU when the refractive index is 1.365. The results show that the reported SPR-based PCF simultaneously implements dual communication window polarization filtering and refractive index sensing. Hence, the designed device has promising applications with good filtering and sensing performance. [ABSTRACT FROM AUTHOR]

A double-sided photonic crystal fiber (PCF) temperature and refractive index (RI) sensor based on surface plasmon resonance (SPR) is reported to simultaneously measure temperature and RI. An arc groove covered with gold is filled with chloroform for temperature detection. The D-shaped plane coated with silver is in direct contact with the analyte to provide the RI. Two independent channels distinguish temperature and RI changes, thus completely solving the cross-sensitivity problem. The sensing characteristics of the plane coating, arc coating, and inner ring coating are discussed. The influence of gold film closure on the optimum RI measurement range was identified, and the best sensing structure of chloroform as a temperature-sensitive material is obtained. The sensing characteristics of different types of metal films are investigated. It is concluded that the band separation may be achieved by plating gold film and silver film in the arc groove and D-plane, respectively. The influence of the central angle of the arc groove on the sensor characteristics was investigated. High-order resonance may be avoided at a 180° center angle. The influence of the thickness of the metal film on the sensitivity of the sensor is studied numerically, and the optimal coating thickness is 50 nm. This work simplifies the selection of the RI range of sensing materials and provides a new approach to solve the high-order resonance and band interference in SPR multi-parameter sensors. [ABSTRACT FROM AUTHOR]

In the paper entitled "Design and Analysis of Dual Band-Notched UWB Antenna Using a Slot in Feed and Asymmetrical Parasitic stub" the authors present a novel elliptically slotted antenna (ESA), with two notched bands for Ultra-wideband (UWB) applications. The authors of the paper "Compact Corner Truncated Fractal Slot Antenna for Cognitive Radio Sensor Network" propose a novel compact antenna for wide spectrum sensing in wireless cognitive radio sensor networks (WCRSN). The author of the work titled "Optimizing Dimensions of Cassegrain Antenna System with Large Magnification Factor" describes a computer-aided design method for optimising Cassegrain antenna dimensions when the feed antenna is located directly behind the main reflector. To improve the image quality, a gain-controlled bi-histogram equalisation operation is conducted on the detailed component of V. In the study entitled "An Effective Brain Tumor Detection System Using Extended Linear Boosting (ELB) Classification Algorithm", tumour cells are found in brain Magnetic Resonance Imaging (MRI) using the Extended Linear Boosting (ELB) classification method, which is a form of soft computing. [Extracted from the article]

In this paper, we design a novel photonic crystal fiber (PCF) chemical sensor wherein the cladding structure is made of a steering-wheel (SW)-shaped large non-circular air-hole. In this PCF, we introduce the rectangular air holes in the core and they are filled with any one of the analytes, namely, water, ethanol and benzene. We use the full-vectorial finite element method (FEM) to optimize the structural parameters. Based on the numerical results, we find that the proposed sensor exhibits a high relative sensitivity of 92.8%, 93.2% and 93.4% for water, ethanol and benzene, respectively, at THz. Furthermore, we study the various optical characteristics of the proposed PCF, namely, birefringence, effective area and numerical aperture (NA). [ABSTRACT FROM AUTHOR]

The additional confinement loss caused by external loads has so far restricted the wide applications of photonic crystal fibers (PCFs). With the rapid development of metamaterials, there is an increasing interest in negative Poisson's ratio (NPR) composite structure due to its outstanding advances in energy and vibration absorption capabilities. In this paper, a novel design concept of PCF with NPR air holes composite structure is proposed. The feasibility of this novel PCF structure is verified by photo-elastic theory and finite element method under compression and impact loads to test the mechanical and optical properties of the fiber. The results show that the PCF with NPR air holes structure effectively suppresses the fiber deformation caused by external loads, thereby reducing the additional fiber confinement loss. Meanwhile, this novel concept displays structural diversity. The macro effective Poisson's ratio of the fiber can still be reduced by maintaining the generalized NPR holes cladding structure, which provides support for the flexible core layer design of PCF under different application requirements. In sum, this design concept subverts the traditional design method of photonic crystal fibers with complex structures and looks promising for future applications in optical fiber sensors. [ABSTRACT FROM AUTHOR]

Recent advances in photonic devices lead researches to be interested in designing all-optical biosensors as new alternatives to large laboratories. In this work, a two- dimensional photonic crystal biosensor based on Graphene Oxide (GO) is developed. The biosensing mechanism is based on the resonance wavelength shift due to refractive index changes of different blood components. The PhC waveguide is designed with an X-shape ring resonator and a hexagonal lattice of (GO) rods in the air background. In the proposed structure, the array of dielectric rods are with a total size of 21.4mm ×16.5 mm. For the optimized structure, the best calculated values of sensitivity (S), quality factor (Q), full width half maximum (FWHM), figure of merit (FOM), and transmission efficiency (TE) are 375 nm/RIU, 14665.8, 0.14nm, 2500 RIU-1, and 99.8% respectively. The important features of this biosensor are excellent FOM, acceptable sensitivity, and high transmission efficiency compared to other studies. [ABSTRACT FROM AUTHOR]

A D-shaped photonic crystal fiber (PCF) polarization filter and sensor with a standard hexagonal arrangement of pores is designed. The effects of geometric parameters, metal film thickness, liquid refractive index, and optical material refractive index on polarization filtering and sensing characteristics are analyzed by the finite element method (FEM). The proposed PCF shows single-polarization filtering in communication window and has ultra-high corresponding bandwidth. At the 1.55 µm communication window band, the confinement loss of the y-polarized core mode is 819.27 dB/cm, while the x-polarized core mode is only 3.45 dB/cm. The crosstalk (CT) reached a maximum of 708.6 dB in the communication bands, and the corresponding bandwidth reaches 1000 µm when the fiber length is 1 mm. Meanwhile, the D-type PCF is widely used in sensing because it avoids filling the gold film and analyte in the internal pores. The change in the thickness of the mental coating from 39 nm to 22 nm provides the proposed PCF with sensing properties. By reducing the refractive index of fiber material, the maximum sensitivity is 10,741 nm/RIU. When the refractive index measurement range of the analyte is specified from 1.33 to 1.36, the average sensitivity reaches 7313 nm/RIU. Good performance enables the proposed compatible filtering and sensing PCF may be used in a wide range of scenarios. [ABSTRACT FROM AUTHOR]

A D-shaped photonic crystal fiber (PCF) with graphene-polymethyl methacrylate (PMMA) stack was employed to determine the refractive index from 1.33 to 1.41 and improve the extinction ratio. The proposed sensor was numerically analyzed using the finite element method. The polishing depth, period of the graphene-PMMA stack, and number of graphene layers on the sensing performance of the proposed structure were evaluated. The results indicate that the spectrum and sensitivity may be modulated. The proposed sensor exhibits a wavelength sensitivity of 2200 nm/RIU, a wavelength resolution of 4.54 × 10−5 RIU, and linearity of 0.9918 with a high extinction ratio. Thus, this device has potential applications in PCF sensors. [ABSTRACT FROM AUTHOR]

A photonic quasi-crystal fibre (PQF) with a high refractive index ring is designed and analysed numerically by the finite element method. In the wavelength range between 1.4 and 1.7 µm, the PQF supports transmission of 150 orbital angular momentum (OAM) modes. The effective refractive index differences between the eigenmodes of the PQF are greater than 10−4, so that the OAM modes can be separated effectively while the single-mode state is maintained in the radial direction. The PQF also exhibits high mode quality and low confinement loss. At 1.4–1.7 μm, the mode qualities of all eigenmodes are higher than 97.6%, the confinement losses are in the range of 10−9 dB/m–10−12 dB/m. Meanwhile the minimum dispersion change is 23.9 ps/(km·nm) and the maximum effective mode area can reach 313 µm2. The PQF has excellent properties and prospects in large-capacity OAM mode division multiplexing communications. [ABSTRACT FROM AUTHOR]

A sensitivity refractive index (RI) sensor based on surface plasmon resonance (SPR) effect in D-shaped high birefringence photonic crystal fibre (PCF) is presented and studied by the finite element method (FEM). Through the designing of air holes arrangement in PCF, the birefringence of optical fibre is improved and the SPR effect of y-polarized core mode is directionally excited. The designed D-shaped PCF with gold film in the damaged air holes enhances the interaction of the evanescent field with the external medium. Simulation results indicate that the sensor has a sensing range from 1.30 to 1.37, and the average spectral sensitivity is 10348.3 nm/RIU. The maximum spectral sensitivity of 19,288 nm/RIU and a high resolution of 5.18 × 10−6 RIU can be obtained at 1.37. This high sensitivity sensor has broad application prospects in life science and other research fields. [ABSTRACT FROM AUTHOR]

To obtain better filtering characteristics and transmission performance, an asymmetric gold-coated photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR) was designed and investigated. The surface plasmon mode is generated by coating gold film to the inner walls of two liquid-filled holes along the y polarization direction. Three air holes with different diameters are introduced near the core which break the symmetry of the primary fiber structure and make the resonance wavelengths of the x polarization and y polarization of the core mode well separated. The filtering performances are evaluated with the finite element method (FEM) based software. The numerical simulation shows that the confinement loss of y polarization is as high as 1375.94 dB/cm at 1.55 µm, while the x polarization loss is only 10.45 dB/cm. Furthermore, the crosstalk (CT) has a maximum of 1186.06 dB in the communication bands when the length of the fiber is 1000 µm. In the range from 1.1 µm to 2 µm, the bandwidth of the filter is approximately 900 nm. The asymmetry of the structure and liquid filling of gold-coated holes enhance the coupling strength of the filter. Meanwhile, the higher confinement loss, crosstalk and wider bandwidth may have useful applications for polarization filters with significance for the design of other filters. [ABSTRACT FROM AUTHOR]

A high sensitivity surface plasmon resonance (SPR) based temperature and magnetic field sensor in a dual-core D-shaped photonic crystal fiber (PCF) with two types of holes is reported. The flat surface of the dual-core D-shaped PCF is coated with ethanol as the temperature-sensitive material. A large diameter hole coated with a gold ring is filled with a magnetic fluid as a magnetic field-sensitive material. Using the finite element method (FEM), the electric field distribution mode is simulated, and the loss spectra of the temperature sensing channel (channel I) and magnetic field sensing channel (channel II) are calculated. The influence of the types of metal films and rings, large hole diameter, small hole diameter, and gold film and gold ring thicknesses on the sensor performance are discussed. The results showed that the reported sensor is able to measure temperature and magnetic field independently and simultaneously due to its dual channels. The influence of temperature on magnetic field measurements is reduced by reducing the hole diameter. The results show that the temperature sensitivity is 1.151 nm/°C and the correlation coefficient is 0.9954 from 20 to 70 °C. The magnetic field intensity sensitivity is 0.0779 nm/Oe from 25 to 200 Oe and 0.0212 nm/Oe from 200 to 275 Oe with correlation coefficients of 0.9937 and 0.9989 across these ranges. This high sensitivity D-shaped PCF sensor will promote the development of high-performance dual-parameter devices. [ABSTRACT FROM AUTHOR]

A polarization beam splitter (PBS) based on a magnetic fluid-filled dual-core photonic crystal fiber is characterized. This is the first time that anisotropy of magnetic fluid is applied to the fiber polarization beam splitter. The designed device is able to separate x and y polarization modes completely by applying an external magnetic field. When the length of the device is 9.905 mm (or 16.795 mm), the maximum bandwidth of the effective working wavelength is 26 nm (or 70 nm) and the tunable magnetic field width is approximately 5 Oe (or 165 Oe) corresponding to magnetic field range from 24 to 29 Oe (or 135 to 300 Oe). By tuning the external magnetic field, the proposed beam splitter may be selected to operate in the S, C, and L bands, and the working wavelength bandwidth and center wavelength are tunable. [ABSTRACT FROM AUTHOR]

An in-fiber optofluidic chemiluminescence (CL) device is reported based on a low-cost microstructured polymer optical fiber (mPOF). The mPOF is composed of a central hole for liquid delivery and a suspended core for optical coupling. Due to the lower processing temperature of mPOF, the difficulty of constructing microfluidic channels is greatly reduced. In addition, the large core diameter of mPOF is more conducive to optical coupling. The microholes are opened on the surface of the mPOF by partial melting to complete the construction of the microfluidic channel. Simultaneously, the response of the CL reaction is detected on-line by the optoelectronic device. Minocycline (MC) was employed as the analyte for on-line optofluidic CL detection. The results show that the device detects aqueous minocycline from 0.0001 to 0.1 g/L with a linear response between 0.001 and 0.01 g/L. The limit of detection is 0.0001 g/L. Moreover, the ability of the device to detect minocycline in blood serum is investigated. The relative deviation from the linear calibration value is within 3.2%. Furthermore, the low-cost in-fiber optofluidic CL device may be integrated with other devices and offers potential in drug safety and medical detection. [ABSTRACT FROM AUTHOR]

A novel Mach-Zehnder interferometer (MZI) with thin core fiber (TCF) – polarization-maintaining photonic crystal fiber (PMPCF) structure for measurement of temperature and strain is proposed and demonstrated experimentally. The MZI is formed by splicing a section of TCF and a section of PMPCF with core offset between two sections of single mode fibers (SMFs). Three sensors with different PMPCF lengths are investigated and compared. Since cladding modes and core mode respond differently to temperature and strain changes, both values can be measured independently. The temperature and strain sensitivities can be achieved simultaneously through the demodulation matrix. For the wavelength-related measurement, the temperature and strain sensitivities are 8.81 pm/°C and 2.98 pm/µε, respectively. In addition, the influence of temperature cross-sensitivity is also analyzed. The proposed sensor offers several advantages such as low cost, simple manufacturing technology, and temperature insensitiveness, which can be further applied in practical sensing. [ABSTRACT FROM AUTHOR]

A novel ring anti-resonance fibre (ARF) is designed and demonstrated for the transmission of orbital angular momentum (OAM) modes. The fibre consists of two layers of negative curvature tubes arranged orderly inside and outside the ring region and OAM modes can be transmitted in the ring region. The properties of the fibre are investigated by the finite element method based on the COMSOL multiphysics software and a manufacturing method is proposed. The fibre shows stable transmission of 30 OAMs in the 1.5–1.6 μm band, low and flat dispersion (5.98 ps/(km nm)), extremely small nonlinear coefficient (0.539 km−1 W−1 at 1.55 μm) and confinement loss (10−9–10−11 dB/m), as well as high OAM purity (larger than 98.295%). Therefore, the structure has immense potential in optical communication. [ABSTRACT FROM AUTHOR]

The goal of the work presented in this investigation is to achieve the efficient parametric interaction of narrow beams (in particular second harmonic generation) using a nonlinear (ferroelectric-LiTaO3) photonic crystal tuned to self-collimation (nondiffractive) regimes. A numerical study of second harmonic generation (SHG) in one-dimensional nonlinear photonic crystals based on a full nonlinear system of equations, implemented by a combination of the method of finite elements and fixed-point iterations, is reported. This model is derived from a nonlinear system of Maxwell's equations that partly overcomes the known shortcoming of some existing models that rely on the undepleted pump approximation. We derive a general solution of SHG in one-dimensional nonlinear photonic crystals structures. Numerical simulations also show that the conversion efficiency of SHG can be significantly enhanced when the frequencies of the fundamental wave are located at the photonic band edges or are assigned to the designed defect states. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the tuning characteristics of a four-layer structure optic fibre Bragg grating (FBG) coated with high refractive index (HRI) overlay. The attention is mainly focused on the analysis of the effects of the mode transition and the mode reorganization on the tuning sensitivity to the overlay HRI of the structure. The cladding diameter of FBG is also considered as a parameter for enhancing the sensitivity of FBG to HRI. Moreover, different cladding modes show different sensitivities. For FBG with negative thermo-optical coefficient coating material, the thermal property of the structure could be effectively suppressed by selecting an optimal fibre cladding diameter. The reported results demonstrate the possibility of this structure can be used as thermal-stable tunable all-fibre photonic device, such as filter, modulator and sensing element. [ABSTRACT FROM AUTHOR]

In this paper, we propose a photonic crystal fiber (PCF) refractive index (RI) sensor based on the surface plasmon resonance (SPR) effect. The coupling and sensing characteristics of the proposed PCF-SPR RI sensor are investigated by the finite element method. The proposed PCF-SPR RI sensor can achieve the dual-wavebands measurement. By controlling the analytes height and incident light wavelength, the PCF-SPR RI sensor shows different sensing performances. The maximum wavelength sensitivities of the proposed PCF-SPR RI sensors can be up to 2000 and 4000 nm/RIU in the wavelength ranges of 0.75 to 1.0 and 1.2 to 2 μm, respectively. [ABSTRACT FROM AUTHOR]

A highly sensitive refractive index (RI) sensor based on the surface plasmon resonance (SPR) phenomenon is proposed and demonstrated. The sensor is composed of a quasi D-shape ten-fold photonic quasi-crystal fiber (PQF) and indium tin oxide (ITO) film. The quasi D-shape and eccentric core structure strengthen coupling between the core mode and surface plasmon polariton (SPP) mode to enhance the sensing sensitivity, while the mechanical strength of the PQF is preserved. The properties of the sensor are determined numerically and optimized by the finite element method. In the RI range of 1.40–1.44, the maximum wavelength sensitivity and average wavelength sensitivity are 62,000 nm/RIU and 26,500 nm/RIU, respectively. Meanwhile, the loss spectra show smaller full-width at half-maximum and maximum FOM of 542.5 RIU−1. This novel sensor which boasts ultra-high-sensitivity and excellent FOM has large potential in the determination of liquid RIs. [ABSTRACT FROM AUTHOR]

A novel fiber sensor based on photonic crystal fiber (PCF) for simultaneous measurement of temperature and humidity is proposed. The PCF is filled with alcohol, which is sensitive to temperature. And it is coated with graphene oxide (GO), which is sensitive to humidity. In the range of 10°C–70°C, the highest temperature sensitivity of the three interference valleys can reach up to 0.182 nm/°C. Similarly, in the range of 30%–70%, the highest humidity sensitivity is 0.109 nm/%RH. This configuration features the advantages of reliable repeatability, strong stability, and it is ideal for environmental detection. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) and surface plasmon polariton (SPP) is substantially developing optical sensing approaches that have been working in a wide range of applications, such as biological and chemical analyte detection, bioimaging, food safety, and environmental monitoring to security. Recently, optical fiber-based Surface plasmon resonance (SPR) sensors has gained much attention due to the invention of Photonic crystal fiber (PCF) and microstructured optical fiber (MOF) which offer compact size and light regulatory competencies in unmatched ways. Moreover, the field of sensing has witnessed another type of plasmonic sensors which are based on metal-insulator-metal (MIM) waveguide structure utilizing surface plasmon polariton (SPP) phenomena. This review paper provides an insight into the technological growths in plasmonic sensors based on optical fibers and the MIM platform. We believe that this paper is one of its kind which provides a diverse range of novel plasmonic sensor structures to its readers. [ABSTRACT FROM AUTHOR]

In this paper, a polarization beam splitter (PBS) based on the gold wire-filled dual-core photonic crystal fiber is proposed. The full-vector finite element method is used to investigate the influences of the fiber structure parameters on the transmission characteristics and coupling length. By appropriately adjusting the fiber structure parameters, the coupling length ratio of 2:1 can be achieved at wavelengths 1.55 and 1.31 μm, so the incident light can be well separated into the two beams with orthogonal polarization states. When the fiber length is 805.3 μm, the maximum extinction ratio (ER) within bandwidth of 60 nm is −132.12 dB at wavelength 1.55 μm. When the fiber length is 1264.9 μm, the maximum ER within bandwidth of 70 nm is −197 dB at wavelength 1.31 μm. By optimizing the fiber structure parameters, a PBS with a length of 249.12 μm, the maximum ER of −112.2 dB, and bandwidth of 120 nm can be obtained. [ABSTRACT FROM AUTHOR]

Specifically, this work aims to achieve a power splitter and polarization separator of a guided light, basing on magnetic properties such as gyrotropy, mode coupling and optimization of geometric parameters of a magneto-photonic fiber. This fiber which makes it possible to split and separate the polarizations is characterized by the opto-geometric optimization of an Y junction based on magnetic fluid in a silicon dioxide photonic crystal fiber, able to separate combination of two guided modes TE/TM, into two waves of the same amplitude and in phase between them, an incoming light wave which arrives at the Y-branch input of the fiber. [ABSTRACT FROM AUTHOR]

A new type of highly sensitive near-infrared birefringent six-core photonic crystal fibre sensor using surface plasmon resonance (SPR) is proposed. By using the full-vector finite element method, the impacts of the fibre parameters on the wavelength sensitivity and amplitude sensitivity are numerically studied. The numerical results indicate that, benefiting from the high birefringent multi-core fibre structure, an average sensitivity of 8083 nm/refractive index unit (RIU) within the wavelength range from 1.532 to 2.02 µm is achieved when the analyte refractive index (RI) lies in (1.372, 1.432). Moreover, the maximum amplitude sensitivity is as high as 226 RIU−1 if the analyte RI is adjusted from 1.372 to 1.382. In consideration of its excellent sensing performance, the proposed SPR multi-core PCF sensor can be applied in environmental, food safety, and (bio)chemical detection. [ABSTRACT FROM AUTHOR]

A wideband tuning of parametric four-wave mixing generation in a liquid-filled photonic crystal fiber is theoretically demonstrated, and influence of its temperature is investigated. The broadband spectrum is generated via a supercontinuum generation process induced by degenerate four-wave mixing (DFWM), for which the thermo-optic coefficient of the oil (the refractive index matching fluid) is considered. The signal band tuning from 734 nm to 923 nm, and the idler band from 1931 nm to 1255 nm, are observed when the temperature increases from 30°C to 90°C. The findings can be applied in many fields, such as CARS. [ABSTRACT FROM AUTHOR]

We propose a hybrid demultiplexer for mode and dense wavelength division multiplexing (DWDM) based on photonic crystal (PhC) and nanowire waveguides. The designed demultiplexer consists of DWDM module using PhC cavities that are defined by an effective Aubry-André-Harper (AAH) bichromatic potential and mode division multiplexing module constructing of asymmetric directional coupler using nanowire waveguides. The performance parameters of the demultiplexer are analysed by two-dimensional finite-difference time-domain method. The results show that the fundamental transverse electric (TE0) modes and first-order TE (TE1) modes of 1573.0 and 1572.2 nm can be demultiplexed simultaneously. The insertion loss is smaller than 0.6 dB, and the crosstalk is smaller than −18.6 dB. Besides, the demultiplexer has a large free spectral range up to 250 nm, which can almost cover the whole range of DWDM system. [ABSTRACT FROM AUTHOR]

In this work, we review our recent investigations on the behavior of a polarization-maintaining passively mode-locked ytterbium-doped laser in two different cavity configurations, namely: fiber-ring (FR) and Fabry-Perot (FP). Opposed to standard configurations that rely on the use of strong filtering within the cavity by including an ad hoc component with this purpose, here the filtering action is solely performed by the spectral overlapping of the different components within the fiber lasers. We found that the lack of a specific filter within the cavity does not deteriorate the performance as compared with previous works. We also report the changes in the output light pulses when the net dispersion of the cavity was varied. Additionally, different lengths of an ad hoc anomalous polarization-maintaining (PM) photonic crystal fiber (PCF) were used as intracavity dispersion compensator, to shift the operation of the laser from net-normal to the net-anomalous regime. The shortest output light pulses [6 ps (FR) and 8 ps (FP)] were obtained when the net-cavity dispersion approached zero. Since the obtained light pulses were far to be transform-limited, we also discuss the possibility of out-of-cavity recompression by using the same PM-PCF mentioned above. After recompression, pulse widths of 3 ps were obtained, limited by the available length of PM PCF. [ABSTRACT FROM AUTHOR]

In this paper, we present guidelines for the simulation of microstructured optical fibers (MOFs), for finding their guided modes and their nonlinear and dispersive characteristics. For the case of hollow-core MOFs, we also present guidelines for studying their photonic bands. Then, we review the results of nonlinear pulse propagation on those MOFs, showing how some of them are particularly well suited to be used as efficient supercontinuum or UV light sources. [ABSTRACT FROM AUTHOR]

We solved the problem of Floquet-Bloch waves propagation in the one-dimensional gyrotropic magnetophotonic crystal with transverse magnetic field. New fundamental solutions of the Hill's equation in crystal layers based on the Floquet theory for a third boundary value problem are obtained in the analytical form. The dispersion equation is found through fundamental solutions. The analysis of the dispersion properties of the structures depending on the material parameters was carried out and extraordinary surface waves inherent only in gyrotropic magnetophotonic crystals have been discovered. [ABSTRACT FROM AUTHOR]

In the paper, a spirally filled solid core chalcogenide-based photonic crystal fibre is proposed, which is engineered to obtain a flattened broad anomalous dispersion profile. The spectrum spanning in the wavelength region from 1.5 to 3.6 μm was achieved by pumping hyperbolic secant pulses with a peak power of 350 W and 85 fs pulse duration, at a wavelength of 2.5 μm, in the optimized design of the fibre. This chalcogenide-based photonic crystal fibre of length 100 mm can be used for wavelength converter between light and microwave. It can find its application as up–down link applications between light and microwave, the light-microwave transducer in LiFi, and WiFi links. [ABSTRACT FROM AUTHOR]

In this paper we present the analysis of soliton propagation in photonic crystal metamaterials. Current analysis considers the case of the complex refractive index for double negative (DNG) materials and for regular metamaterials. The analytical solution of the nonlinear Schrödinger (NLS) partial differential equation is realized through the traveling wave model. The analysis reveals the existence of soliton pulse propagation under specific constraint conditions necessary for the existence of the soliton solutions. The analytical solutions are validated by the results obtained through simulations. The analysis results give design guidance of waveguide structures able to support undistorted soliton wave propagation. [ABSTRACT FROM AUTHOR]

A novel structure photonic crystal fibre (PCF) supporting orbital angular momentum (OAM) modes is proposed. The transmission layer is a ring core with high refractive index, sandwiched between the inner air-hole cladding and the outer cladding composed of nonuniform air-holes periodically arranged in silica. The diameters of the air-holes in the outer cladding gradually increase in the radial direction. The simulation results show that the designed PCF is capable of supporting 54 OAM modes over the 650 nm bandwidth ranging from 1200 nm to 1850 nm, and possesses some advantages in low confinement loss and flat dispersion, that is, the confinement loss is low to the order of magnitude of 10 − 11 dB/m and the dispersion slope is less than 0.2 ps/(n m 2 ⋅ km) . [ABSTRACT FROM AUTHOR]

Propagation properties of photonic crystals with defect are analyzed by the precise integration time domain (PITD) method in the paper. The precise integration is applied to the finite difference time domain in this method. The Yee cell differential discretization technique is used in space, and the precise integration method is adopted in time. The correctness of the method is demonstrated by calculating the one-dimensional photonic crystals with defect. The transmission coefficients of the transverse electric (TE) and transverse magnetic (TM) modes in the two-dimensional photonic crystals with defect are also obtained by the method. Furthermore, the stability, precision and efficiency of the method are discussed. Numerical results reveal that the PITD method is not limited by the Courant stability condition and has higher calculation precision and efficiency, which provides a new and effective analytical method for studying the propagation properties of photonic crystals with defect. [ABSTRACT FROM AUTHOR]

A novel one-dimensional photonic crystal design for ripple suppression of third-order dispersion in ultrafast laser systems has been introduced. We investigated and compared the compensation behaviour of a simple photonic crystal and the proposed graded index structure with the same total thicknesses and periodicity at the near infrared region by the transfer matrix method. The results reveal that implementing the proposed graded index structure removes the pulse wings, produces clean pulses without the use of additional optical elements and also results in a dramatic reduction in the fluctuations of the group delay and third-order dispersion curves. [ABSTRACT FROM AUTHOR]

An effective filler dispersion within a polymeric matrix is known to be a crucial requirement for obtaining the desired performance from a composite. A quantification of this parameter cannot be always easily achieved and several methodologies have been proposed so far, generally based on complex image processing algorithms. However, no standard has been established yet. In order to contribute to the quantitative evaluation of the filler dispersion in a polymeric matrix, a novel straightforward two-dimensional alternative method based on the analysis of electron microscopy micrographs is here proposed. Several case studies were considered to test the reliability of the approach, providing as resulting output, either a qualitative polar plot representative of the analyzed image and an index to measure the filler dispersion. [ABSTRACT FROM AUTHOR]

In this paper, a novel two-dimensional photonic crystal based all-optical AND/OR logic gates are designed, simulated and optimized. The structure is built on a linear square lattice photonic crystal platform. A multi-wavelength operation, together with a simultaneous operation, is achieved at ultra-high bit rates. The concurrent operation is attained without altering the proposed design continuously, as stated in the literature. It provides simplicity because there is no auxiliary input required along with the absence of externally attached phase shift units. The enhancement process has been done to the rod radius. A magnificent representation tool is developed. The benefit of the mentioned tool lies in the data combination of different operating wavelengths, contrast ratio, and bit rate; which will establish an efficient optimization process. Each gate is enhanced independently, then an overall improvement has been done. As a result, the operation at 1.52 µm will provide a successful multi logic gate operation with ultra-high bit rates of 6.76 and 4.74 Tbit/s for AND and OR logic gates, respectively. The design has an acceptable size of (19.8 × 12.6 µm) and a contrast ratio of 9.74 dB and 17.95 dB for the designed AND and OR gate, respectively. The design is highly sensitive to the waveguide length to verify the gates on demand. [ABSTRACT FROM AUTHOR]

A novel fiber sensor composed by two single mode fibers and long period fiber grating based on a photonic crystal fiber prepared by periodic discharge heating has been experimentally investigated to measure refractive index and temperature. A Mach-Zehnder interferometer was formed due to the presence of two fusion spliced collapsed regions in the photonic crystal fiber. The resonance dip and interference pattern were differently influenced by the ambient disturbance, so the dual-parameters were simultaneously measured by analyzing the characteristics of transmission spectrum. After the experimental measurements, refractive index and temperature sensitivities of 117.28 nm/RIU and −86.29 pm/°C were realized. Therefore, the reported sensor with advantages of easy fabrication, simple structure, and small size has the potential for simultaneous refractive index and temperature measurements involving biochemical sensing applications. [ABSTRACT FROM AUTHOR]

A novel mid-infrared Ge20Sb15Se65 chalcogenide-based single-polarization single-mode (SPSM) photonic crystal fiber (PCF) with rectangular latticed circular air holes is proposed. The properties of SPSM bandwidth, confinement loss, and nonlinearity are analyzed in the 3 μm~8 μm mid-infrared region using the finite -difference time-domain (FDTD) method. The influences of different geometrical parameters on the properties of SPSM-PCF are analyzed. All numerical computational results reveal that for the optimized geometrical parameters, the proposed PCF can deliver a SPSM region of more than 2.3814 μm with high nonlinearity of 3,705 w−1 km−1. Therefore, such a SPSM-PCF will become an excellent candidate for mid-infrared photonic. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance (SPR) sensor comprising a photonic crystal fibre (PCF) with an annular analyte channel outside the fibre is described and analysed. The losses of the sensor are analysed by the finite element method (FEM) with the boundary condition of a perfectly matched layer (PML). The influence of the structural parameters on the performance of the sensor is investigated based on the loss spectra of the fundamental mode. The relationship between the resonance wavelengths and analyte refractive indexes is established for refractive indexes ranging from 1.395 to 1.425. An average spectral sensitivity of 12,592.86 nm/RIU can be achieved in the sensing range corresponding to a resolution of 7.94×10−6 RIU. The maximum spectral sensitivity and the maximum figure of merit (FOM) are as high as 22,807.14 nm/RIU and 595.78, respectively. [ABSTRACT FROM AUTHOR]

In this article, confinement loss in hexagonal lattice photonic crystal fiber has been investigated, by using COMSOL Multiphysics based on finite element method. The proposed structure consists of four circular air holes rings, where three circular air holes near the center are replaced by elliptical air holes, which have a major and minor diameter. The Confinement loss was studied in term of minor diameter and wavelength in the range of about 1200–1800 (nm). We realized that the rise of minor diameter lead to decreases of imaginary part of effective index and therefore the confinement loss reduces. [ABSTRACT FROM AUTHOR]

The article describes a novel doped CS2 core photonic crystal fiber with high negative chromatic dispersion. The proposed design is simulated through a full-vector finite element method and anisotropic perfectly matched layers. The numerical results show that we can achieve a negative dispersion coefficient of −5600 ps/(nm km) almost at the wavelength of 1.55 μm by carefully adjusting the proposed PCF structure parameters. The proposed PCF may have great potential applications in dispersion compensating, optical parametric amplification, and optical fiber communication. [ABSTRACT FROM AUTHOR]

In this paper, a new double-photonic crystal fibre (D-PCF) is proposed and numerically investigated, result shows that can support angular momentum (OAM) mode transmission up to 26. Based on As2S3 substrate, the proposed D-PCF is composed of three well-ordered air-hole rings in the cladding and another several air-hole rings at the centre. Due to the large effective index difference greater than 10−4 between eigenmodes, OAM can be well separated with the proposed D-PCF. In addition, the confinement loss of less than 7 × 10−9 dB/m for all eigenmodes is obtained with wavelengths spanning from 1.25 to 2.1 µm, where the optical wave can be confined closely within the core of D-PCF. With these beneficial properties, the designed D-PCF could enable large-capacity transmission in high-speed communications. [ABSTRACT FROM AUTHOR]

We model an optical switch with a variable gain based on the optical parametric amplification in a photonic crystal fibre (PCF). By solving the coupled amplitude equations, the switch gain as a function of the power, wavelength and the state of polarization (SOP) of the control wave as well as the signal wavelength is simulated. The results show that the switch gain is increased by increasing the control power and the maximum gain is obtained for a specific SOP of the control wave. Also, the proposed switch has ultrahigh speed and provides a very wide and flat gain over the C-band without changing the operating wavelength. [ABSTRACT FROM AUTHOR]

A triangular lattice photonic crystal fibre is presented in this paper for residual dispersion compensation. The fibre exhibits a flattened negative dispersion of −992.01 ± 6.93 ps/(nm-km) over S+C+L wavelength bands and −995.83 ± 0.42 ps/(nm-km) over C-band. The birefringence is about 4.4 × 10−2 at the excitation wavelength of 1550 nm which is also very high. Full vector finite element method (FEM) with a perfectly matched absorbing layer (PML) boundary condition is applied to numerically investigate the guiding properties of this PCF. The fibre operates at fundamental mode only. All these properties endorse this fibre as a suitable candidate for compensating residual dispersion and polarization maintaining applications. [ABSTRACT FROM AUTHOR]