Size Of Air Holes Research Articles

Hybrid hexa-octagonal photonic crystal fiber with excellent guiding properties for sensing and communication applications

Abstract A novel hybrid hexa-octagonal photonic crystal fiber (PCF) is designed by integrating a hexagonal arrangement of elliptical air holes in the core using soft glass and an octagonal lattice of circular air holes in the cladding. This study presents a comparative analysis of the fiber parameters, including confinement loss, non-linearity, effective area, birefringence, and chromatic dispersion, for two configurations: (i) hybrid hexa-octagonal PCF with a horizontal arrangement of air holes in the core, and (ii) hybrid hexa-octagonal PCF with a vertical arrangement of air holes in the core. Both configurations are examined by varying the pitch size, arrangement, and shape of air holes while maintaining identical design and operational features. Simulations are conducted using the full vector finite element method (FEM). Numerical results indicate that the confinement loss for vertically and horizontally arranged air holes is 1.098 × 10−5 dB km−1 and 1.0743 × 10−5 dB km−1, respectively. High birefringence values of 0.07366 and 0.00434, and chromatic dispersion values of −3404.665 ps nm−1 km and −3391.6705 ps nm−1 km, respectively, are obtained at an operating wavelength of 1.55 µm, making the fiber suitable for sensing and communication applications. The designed hexa-octagonal PCF has potential applications in the fiber optic sensing due to its assorted features.

Simulation analysis of a photonic crystal fiber refractive index sensor based on a double-layer film structure and surface plasmon resonance technology

A photonic crystal fiber surface plasmon resonance sensor based on a double-layer membrane structure is designed and analyzed. In the simple sensing structure with only one air hole size, TiO2 and Au layers with specific thicknesses are sequentially coated on the optical fiber to form a double-layer structure. The sensing characteristics of the double-layer membrane structure are studied by the finite element method. Compared to the single-layer membrane structure, the double-layer membrane sensor has significant sensing properties such as a better wavelength sensitivity and a smaller full width at half maximum in the loss spectrum. In the refractive index range between 1.37 and 1.43, the maximum wavelength sensitivity and average wavelength sensitivity of the sensor are 19,900 nm/RIU and 7417 nm/RIU, respectively, and the resolution can be up to 5.03×10−6RIU. The proposed photonic crystal fiber optic sensor achieves high performance with a simpler sensing structure than previous photonic crystal fiber optic sensors, and eliminates the step of polishing, which will greatly reduce the difficulty of actual fabrication and the error due to uneven polishing. The results show that the photonic crystal fiber optic sensor with a double-layer membrane structure has excellent performance. Due to its high sensitivity and resolution, it has great potential for applications in environmental monitoring, biosensing and chemical sensing.

Design and analysis of the C6H6-filled circular photonic crystal fiber with ultra-flat dispersion for broadband supercontinuum generation with peak power of 130 W and 250 W

This article introduces a new model of a circular silica-based photonic crystal fiber with a hollow core filled with C6H6. The difference in the air hole size and the distance between them in the first ring around the core has a profound effect on the dispersion, leading to ultra-flat dispersion with values as low as ±0.996 ps nm−1· km in wavelength range 0.74 µm. The high nonlinear coefficient of several 1000 W−1 · km−1 and the low confinement loss of a few tens of dB m−1 suggest proposing three fibers with dispersion and nonlinear properties suitable for broadband supercontinuum generation at low peak power. The influence of peak power on the broadening of the supercontinuum spectrum is also investigated. Fibers with a flat all-normal dispersion profile provide a smooth spectrum with bandwidths of 1.215 and 1.626 µm at 30 dB with a peak power of 250 W. A fiber with an anomalous dispersion regime generates a supercontinuous spectrum, broadening to 3.868 µm in the mid-infrared region (2.467 µm bandwidth at 30 dB) under laser pulse excitation with 130 W peak power. Our results provide further insights into the generation of broadband mid-infrared supercontinuum using liquid-core silica-fibers, which have great potential for applications in the fields of optical communications and optical sensing.

Wide-mode-area slow light waveguides in valley photonic crystal heterostructures

We designed slow-light waveguides with a wide mode area based on slab-type valley photonic crystal (VPhC) heterostructures which are composed of a graphene-like PhC sandwiched by two topologically distinct VPhCs. The group velocity of the topological guided mode hosted in a VPhC heterostructure can be slowed down by shifting the VPhC lattice toward the graphene-like PhC at the domain interfaces. Simultaneously, the mode width of the slow-light topological guided mode can be widened by increasing the size of the graphene-like PhC domain. We found that employing the graphene-like structure at the center domain is crucial for realizing a topological single-guided mode in such heterostructures. Furthermore, the impact of random fluctuations in air-hole size in the graphene-like domain was numerically investigated. Our simulation results demonstrate that the transmittance for the slow-light states can be kept high as far as the size fluctuation is small although it drops faster than that for fast-light states when the disorder level increases. The designed wide-mode-area slow-light waveguides are based on hole-based PhCs, offering novel on-chip applications of topological waveguides.

Supercontinuum generation in C6H5NO2-core photonic crystal fibers with various air-hole size

In this paper, we demonstrated the ability of a hexagonal photonic crystal fiber (PCF) with a hollow core infiltrated with nitrobenzene (C6H5NO2) to generate a broad SC spectrum at low peak powers. Due to the non-uniformity of the air hole diameters, our new design allows for simultaneous optimization of features, resulting in near-flat, near-zero dispersion, a small effective mode area, and low attenuation for efficient spectral broadening. We selected two optimal structures from the simulation results to analyze the nonlinear properties and supercontinuum generation. The first fiber, #HF1, with a lattice constant of 1.0[Formula: see text][Formula: see text]m and a filling factor of 0.45, operates in all-normal dispersion and produces spectral SC ranging from 0.81[Formula: see text][Formula: see text]m to 1.919[Formula: see text][Formula: see text]m with a pump wavelength of 1.56[Formula: see text][Formula: see text]m, a pulse duration of 90[Formula: see text]fs, and peak power of 0.133[Formula: see text]kW propagated in a 1 cm fiber length. The #HF2 fiber (lattice constant of 2.0[Formula: see text][Formula: see text]m, filling factor of 0.3) has an extended SC spectrum from 0.792[Formula: see text][Formula: see text]m to 3.994[Formula: see text][Formula: see text]m, a pump wavelength of 1.55[Formula: see text][Formula: see text]m, a pulse width of 110[Formula: see text]fs, a peak power of 0.273[Formula: see text]kW propagated in a 15[Formula: see text]cm fiber length. The proposed fiber may be a new-generation optical fiber suitable for low-peak power all-fiber optical systems to replace glass-core glass fiber.

A study on the optical properties of a novel flower-core photonic crystal fiber infiltrated with CCl4

A novel design of photonic crystal fiber with a flower-core is proposed for the first time to optimize dispersion suitable for broadband supercontinuum generation. The numerical simulation of the propagation of light modes in optical fibers is computed by solving Maxwell's wave equations with the full-vector finite-difference eigenmode method. As a result, near-zero ultra-flat all-normal and anomalous dispersion was achieved with fluctuations of ±0.978 ps/nm.km in the 294 nm wavelength region and ±1.168 ps/nm.km in the 432 nm wavelength region, respectively. Furthermore, the dispersion value at the pump wavelength is about 10 times lower than in previous papers. The combination of CCl4 infiltration into the hollow core and the air hole's size heterogeneity in the cladding also enhances the nonlinear properties of the fibers. The effective mode areas less than 2 µm2 at the pump wavelength can help the supercontinuum spectrum to broaden further towards the red wavelength region. Three fibers with structural parameters Ʌ = 0.8 µm, d1/Ʌ = 0.45, Ʌ = 0.9 µm, d1/Ʌ = 0.5, and Ʌ = 0.9 µm, d1/Ʌ = 0.45 are proposed for supercontinuum generation with low peak power due to the nonlinear coefficients as high as hundreds W−1.km−1. These fibers are a new class of optical fibers, highly efficient laser sources that replace traditional glass-core optical fibers.

Study on Optical Features of Circular Photonic Crystal Fibers with Various Air-hole Size

: In this workwe proposed a newly designed photonic crystal fiber (PCF) with a circular lattice, the difference between the air-hole diameters of the first ring and the other rings makes it possible to improve the nonlinear properties of fibers. We investigated the effect of varying the filling factor (d1/Ʌ) and lattice constant (Ʌ) on the nonlinear characteristics of photonic crystal fibers in the 0.5 - 2 µm wavelength range. The advantages of these photonic crystal fibers are the flat and near-zero dispersion, low attenuation, and high nonlinear coefficient. From simulation results, we have selected three optimal structures (Ʌ = 1.0 μm; d1/Ʌ = 0.4, Ʌ = 0.8 μm; d1/Ʌ = 0.6, and Ʌ = 0.8 μm; d1/Ʌ = 0.65) to analyze the nonlinear characteristics at the pump wavelengths. The proposed fibers are valuable for supercontinuum generation.
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Investigation of bandwidth in multimode W-type microstructured plastic optical fibers

By employing the time-dependent power flow equation (TD PFE), we examine the bandwidth in multimode W-type (double clad) microstructured plastic optical fibers (mPOFs) with a PMMA (polymethyl methacrylate) solid core for parametrically varying depth and width of the intermediate layer (IL) (inner cladding). The investigated W-type mPOF's bandwidth was calculated for various configurations of the air-holes in the inner cladding and varied launch excitations. We obtained that results for smaller inner cladding air-holes at longer fiber lengths exhibit greater bandwidth. On the other hand, for shorter fibers, the launch beam which only excites guided modes, has no effect on the bandwidth due to the air-hole size. The W-type mPOF with a narrower inner cladding has a greater bandwidth. The bandwidth is also larger for a narrow launch that only excites guided modes as opposed to a wider launch that excites both guided and leaky modes. Therefore, the bandwidth increases as the width of the IL is reduced, or by decreasing the diameter of air-holes in the IL, or by exciting only guided modes. W-type mPOFs can be more easily tailored for a specific use in optical fiber sensors and communications because to their programmable properties.

Research on novel variable air-hole photonic crystal fiber

Abstract A novel PCF (photonic crystal fiber) with variable air holes is designed to solve the problem that it is difficult to obtain flatted dispersion and low confinement losses simultaneously it can obtain flatted dispersion and low confinement losses by changing the size of air hole in the cladding. The structure of the optical fiber is analyzed by using FVFEM (full vector finite-element method) and APML (anisotropic perfectly matching layer) boundary conditions. The effective refractive index of the air hole at 1.55 μm is n 0 = 1, and that of quartz is set as 1.45,under these conditions, the simulation results show that the optical fiber has super-flat dispersion in the wavelength range of 1.25–1.78 μm, the dispersion varies ranges from 0 ± 0.68 (ps/nm km), and the confinement losses is less than 10−3 dBb/m.

Ultra-compact on-chip one dimensional nanobeam cavity for simultaneous temperature sensor and bandstop filter at 2 μm waveband

Optical sensors with compact size are key components in on-chip highly dense integrated devices. An ultra-compact one dimensional photonic crystal nanobeam cavity (1D-PhC-NBC) structure with the functionalities of both sensing and filtering is proposed. To confine the light into center of cavity to obtain a fundamental resonant mode and filter out the light belonging to other frequency band at the same time, the structure consists of one 1D-PhC-NBC sensor (1D-PhC-NBCS) and one 1D-PhC-NBC filter (1D-PhC-NBCF). In the region of 1D-PhC-NBCS, the waveguide width is tapered from the center to the end and the size of air holes is kept the same. In the region of 1D-PhC-NBCF, the waveguide width and the size of air holes are the same. The 1D-PhC-NBCF is serially located on the behind of 1D-PhC-NBCS to obtain the desired resonant peak. With three dimensional finite-difference time-domain (3D-FDTD) simulation, the results show that an optimal resonant frequency of air mode and mirror strength are achieved when the semi-major and semi-minor axes are equal to 0.38 μm and 0.14 μm, and the width of waveguide is tapered from 1.07 μm to 0.83 μm, respectively. The fundamental resonant peak of 1940.85 nm is obtained in 1D-PhC-NBCF when the semi-major axis of 0.27 μm and semi-minor axes of 0.08 μm are chosen. The sensitivity of 198.09 nm/RIU is achieved with the increase of temperature. The size is about a half of the previous reported nanobeam structure due to the that filter at one side of the structure. Particularly, the minimum size of the proposed structure is only 12.6 μm × 1.1 μm. Therefore, it is a promising method to construct highly integrated sensor arrays for on-chip applications.

Design of a compressed hexagonal dual-core photonic crystal fiber polarization beam splitter with a liquid crystal filled air hole

A compressed hexagonal dual-core photonic crystal fiber (CH-DC-PCF) polarization beam splitter (PBS) with a liquid crystal filled air hole is designed. The designed CH-DC-PCF has different sizes of air holes, which are arranged in a compressed hexagonal structure in the cladding region and introduce the birefringence. In addition, the nematic liquid crystal is filled into the central air hole to enhance the beam splitting effect. To obtain a shorter PBS, the structure parameters of the CH-DC-PCF are optimized by the finite element method. The simulation results show that the length of the proposed CH-DC-PCF PBS is 109.5 μm, and the corresponding extinction ratio (ER) reaches the first peak value of 86.07 dB at wavelength 1.494 μm, then 63.14 dB at wavelength 1.55 μm, and the second peak value of 83.35 dB at wavelength 1.553 μm. Moreover, the ER is higher than 20 dB in the wavelength range of 1.402 to 1.682 μm, so the bandwidth of the PBS is up to ∼280 nm, covering the S + C + L + U communication band.

High Birefringence D-Shaped Germanium-Doped Photonic Crystal Fiber Sensor.

In this work, a surface plasmon resonance (SPR) sensor based on a D-shaped germanium-doped photonic crystal fiber (PCF) is proposed. The finite element method (FEM) is introduced to analyze the structure parameters, such as germanium-doped concentration, lattice pitch, and air hole size. In addition, the coupling properties and birefringence properties of PCF are also studied. The computer simulation results indicate that two different surface plasmon polariton (SPP) coupling modes are produced on the polished surface, covered with metal film, when the analyte refractive index (RI) is . Then, with the increase of the RI, the incompleteness of one of the coupling modes will be transformed into the complete coupling. The effect of germanium concentration on the birefringence is also analyzed. It has an optimal wavelength sensitivity of 5600 nm/RIU when the RI is 1.37. This sensor exhibits a maximum birefringence of 1.06 × 10−2 and a resolution of 1.78 × 10−5 RIU with high linearity.

Design and analysis of surface plasmon resonance based photonic crystal fiber sensor employing gold nanowires

A simple design of photonic crystal fiber (PCF) sensor which utilizes surface plasmon resonance (SPR) for refractive index detection is inspected to achieve high sensitivity. The offered sensor comprises of air holes in square lattice arrangement where two gold nanowires as a plasmonic material are located at the surface. Size-dependent plasmonic features of nanowires facilitates the coupling of SPR and fundamental core modes which leads to enhancement of sensor performance. With the propose of achieving the best result, the geometrical structure including the size of air holes and their arrangement in the PCF and also the size of nanowires are examined, in this work. Sensing performance of the proposed sensor is evaluated by finite element method using Comsol Multiphysics software. In y-polarization mode, the maximum wavelength and amplitude sensitivities of 50000 (nm/RIU) and 672.2 1/RIU have been obtained. The corresponding maximum values of figure of merit and resolution are 250 (1/RIU) and 2×10−6(RIU), respectively. This sensor includes remarkable prospect in chemical and biomedical detection because of its high sensitivity and low fabrication complexity. For example, the sensor performance is investigated for the cervical cancer cell detection and high sensitivity as 40000 (nm/RIU) is obtained.

Design of high-birefringence photonic crystal fiber based on As2Se3

A photonic crystal fiber is designed with chalcogenide glass As2Se3 as the base material. As2Se3 has a high refractive index and a high nonlinear refractive index; as a result, it has a desired application for strengthening birefringence and nonlinearity. The outer layer of the fiber is a regular decagonal structure composed of four layers of circular air holes, and the inner cladding area is composed of four elliptical air holes arranged in a diamond pattern. The influence of the size of the circular air holes in the fiber cladding, the thickness between each layer, and the size and position of the elliptical air holes in the inner cladding area on the birefringence is analyzed and studied using the full vector finite element method. The results show that the birefringence value of the fundamental mode of the fibers is 0.108 at a wavelength of 1.55 μm, and at the same time, the nonlinear coefficients of the X and Y polarization states are 240 and 197 m − 1 · W − 1, respectively.

Hemoglobin sensor based on external gold-coated photonic crystal fiber

Ahighly sensitive photonic crystal fiber-based hemoglobin sensor is numerically simulated and studied. Variations of the fundamental mode loss and dependent sensitivities (wavelength and amplitude) are analyzed in the reference of gold layer thickness, lattice period, cladding air holes size, and different analyte refractive indices. This sensor structure offers the highest amplitude sensitivity of 2080 RIU−1 with a resolution of 4.80 × 10−6 RIU at a hemoglobin refractive index of 1.38. Additionally, this sensor can be fabricated in the length of millimeter with high-quality factor of 239. This amended surface plasmon resonance-based sensor might be suitable for recognizing diseases related to a blood disorder.

Dispersion compensation for orbital angular momentum mode based on circular photonic crystal fiber

In this work, a circular dual-core photonic crystal fiber is proposed for dispersion compensation for the controllable orbital angular momentum (OAM) mode by the inner-outer core mode coupling. This design can simultaneously realize a negative dispersion of up to −3039.45 ps nm−1 km−1 for OAM mode HE31 and a high effective index separation of 2.15 × 10−3 within scalar linearly polarized (LP)21 mode group (HE31 and EH11) at 1.55 µm, ensuring HE31 vortex mode robust propagation without channel crosstalk. Evolution of the combined effective index, OAM phase, and electric field is systemically verified functioning as wavelength during the inner-outer mode coupling. Structural parameter dependence of negative dispersion is demonstrated with respect to lattice constant, air hole size and air-filling fraction, remarkably suggesting that negative dispersion dip at phase-matching wavelength exhibits an enhanced blue shift with lattice constant of inner cladding increasing but a red shift with lattice constant of outer cladding. The feasibility of this design is demonstrated with an achievement of negative dispersion of −1773.21 ps nm−1 km−1 for EH11 mode at wavelength 1.55 µm by tuning the structural parameter. This design is expected for fiber applications in OAM-based optical communication systems.

Design of a novel star type photonic crystal fiber for mid-infrared supercontinuum generation

In this work, we have designed two simple photonic crystal fibers (PCFs) with the highly nonlinear chalcogenide material of Ge11.5As24Se64.5 for broadband mid-infrared supercontinuum generation. The hexagonal lattice of air holes in a star type arrangement has been considered in the designs, where only two different air hole sizes and a constant pitch are employed. The study shows that the diameter of the air hole has significant influence on both the dispersion and the nonlinearity parameters of the PCFs. The numerical solutions of the generalized nonlinear Schrödinger equation (GNLSE) for a secant hyperbolic input pulse at different pumping wavelengths at mid-infrared region are investigated by varying input pulse power and fiber lengths. About 3000 nm wide supercontinuum can be generated at pumping wavelength of 2400 nm and input pulse power of 3000W with the designs. Thus, the designs of the PCF can be employed for generating supercontinuum to be useful for medical imaging, bio-sensing, spectroscopy, wave division multiplexing (WDM) systems, and optical communication systems.

Temperature effects on surface plasmon resonance sensor based on side-polished D-shaped photonic crystal fiber

A comprehensive temperature Drude theoretical mode has been established to study the temperature effects on the side-polished photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor. In the theoretical model, the temperature dependence coefficients of fiber material refractive index (RI), sensing film thickness and metal-dielectric function have been considered. The finite element method (FEM) is used to study the influence of side-polished depth, metal thickness, air hole size, and lattice constant on sensing performance with findings as following: (1) the dependence of the resonance wavelength on temperature is almost unaffected by duty ratio or lattice pitch of PCF; (2) the peak loss of the PCF SPR sensor with small lattice pitch (or increased duty ratio) is more sensitive to temperature variation; (3) for the sensor working in intensity interrogation mode, linear relationships can be found between the peak loss versus the RI and temperature. Moreover, we fabricate a side-polished D-shaped PCF SPR sensor by a wheel polishing setup, and the experimental results display a good agreement with the theoretical investigations. This study offers a detailed way to analyze the temperature effects on the sensor, and may lead to the better design and the data-progress improvement for D-shaped PCF SPR sensor.

Research on the dispersion characteristics of silica-based ring-core photonic crystal fiber used to transmit orbital angular momentum modes

In this paper, based on the silica-based ring-core photonic crystal fiber (PCF) used to transmit orbital angular momentum (OAM) modes, the effects of central air hole and first-layer cladding air holes on the dispersion of ring-core PCF are analyzed. As a result, it is found that the sizes of air holes have a regular regulation effect on the dispersion of PCF. Furthermore, a ring-core PCF which can support 44 OAM modes in communication band is proposed. The characteristics of the designed ring-core PCF, such as number of supported modes, dispersion, nonlinear coefficient and confinement loss, are systematically analyzed by using the finite element method (FEM). In summary, the conclusion is of guiding significance for the design of silica-based ring-core PCF structures, and the designed ring-core PCF has potential applications in the high-capacity fiber communication.

Multimode hexagonal photonic crystal fiber for extremely negative chromatic dispersion and low confinement loss

In this paper, a multi-mode hexagonal photonic crystal fiber is proposed. The cladding of the proposed PCF has circular air-holes arranged in five hexagonal rings whereas core has tiny circular air-holes arranged in two different rings. This structure is designed and simulated using COMSOL Multiphysics which is based on finite element method. The performance parameters viz chromatic dispersion, confinement loss, V-number, effective area, and nonlinearity coefficient are determined by wavelength interrogation method and optimized with respect to size and number of tiny circular air-holes in the inner ring of the core. The results show that V-number is greater than 3.1416 over wide range of spectrum which confirms the multimode operation of the fiber. The obtained value of performance parameters at 1.55 µm wavelength are; negative dispersion (− 2159 ps nm−1 km−1), confinement loss of (3.61 × 10−3 dB km−1), V-number (3.66), effective area (3.44 µm2), and nonlinearity coefficient (27.5 w−1 km−1). The extremely negative dispersion alongwith very low confinement loss at the center wavelength of main communication window, i.e., 1.55 µm suggests that the proposed PCF is best suited for the dispersion compensation.