Elliptical Air Holes Research Articles

Ultrahigh-[formula omitted] Fano resonance in a cavity-waveguide coupled system based on second-order topological photonic crystals with elliptical holes

We present a novel configuration of second-order topological photonic crystal (SOTPC) comprising interconnected dielectric material with elliptical air holes. Based on this SOTPC design, we construct a topological corner state (TCS) cavity and a topological edge state (TES) waveguide. Through the coupling of the TCS cavity with the TES waveguide, we establish a topological cavity-waveguide coupled system (TCWCS) that exhibits an ultrasharp asymmetric topological Fano resonance. Numerical simulations demonstrate that the proposed TCWCS achieves an exceptionally high quality factor exceeding 108, surpassing previously reported results by several orders of magnitude. Moreover, the refractive index sensing application implemented with TCWCS shows a sensitivity of 278 nm/RIU and a figure of merit surpassing 107 1/RIU. Notably, our simulations reveal that the lineshape and quality factor of the Fano resonance, as well as the index sensing performance in the TCWCS, are highly robust against structural defects. The demonstrated capabilities of the TCWCS open up avenues for further exploration and development in the field of topological photonics based on our proposed SOTPC.

A novel high-sensitivity sensor with asymmetric elliptical shaped exposed core and gold coating for sucrose and chemical concentration detection

The article introducing an innovative exposed core SPR biosensor employing an asymmetrical elliptic air hole PCF known for remarkable sensitivity. Gold-plated fiber sensor detects changes in refractive index. This sensor effectively covers a RI scale of 1.28 to 1.42 for analytes, showcasing its versatility in simultaneous detection. Taking into account the RI change at the outer surface, attractive sensing implementations such as optimal wavelength sensitivity of 97,000 nm/RIU and optimal amplitude sensitivity of 529.20 RIU−1 are attained. Furthermore, with a resolution of 9.09 × 10−6 RIU, a figure in merit of 170 RIU−1, an FWHM of 570 nm, and a detection accuracy of 0.0166 nm−1, the suggested sensor is impressive. This suggested sensor finds application in monitoring sucrose solutions across a spectrum ranging from 0% to 45% chemical concentration over time. It has an ideal amplitude sensitivity of 530.95 RIU−1 and an ideal wavelength sensitivity of 10,000 nm/RIU for sucrose solutions at the 40% concentration level. Furthermore, the sensor shows an ideal wavelength sensitivity of 35,000 nm/RIU and an ideal amplitude sensitivity of 793.80 RIU−1 for the detection of 2-propanol. Nevertheless, beyond sucrose noticing auspicious sensing qualities by the suggested sensor its feasibility for impact fully identifying a range of biochemical and organic samples. As a result, the proposed sensor holds promise as an exemplary choice the realms in biomedical sensing, the detection of lower RI analyses as well as chemical analysis. Streamlining practical application, the sensor's structure incorporates eight elliptical air holes, uncomplicated readily manufactural with existing technologies.

An excellent super-polarization-independent optical directional coupler based on dual-core photonic crystal fibre with a bandwidth of 390 nm

In this work, a novel structure of dual-core photonic crystal fibre (PCF) is proposed to realize the super-polarization-independent optical directional coupler, based on the feasibility of optical fibre manufacturing process and the need of practical application into account. The introduced fluorine-doped elliptical cores with a rotation angle of 45 degrees successfully realize the super-polarization-independent coupling performance within the effective wavelength range of 1230–1620 nm, with a difference in coupling ratios between two polarized lights of less than 0.004%. In other words, it counteracts the negative effects of the introduction of dual cores on the structure’s symmetry. This greatly reduces the difference in coupling ratio between the two polarization states and effectively eliminates the polarization-dependence of the dual-core PCF. In addition, when compared to traditional elliptical air holes, the solid elliptical structure offers greater ease of control, making manufacturing less challenging. Consequently, this innovative structure is poised for widespread adoption in today’s optical communication networks.

Improving Temperature-Sensing Performance of Photonic Crystal Fiber via External Metal-Coated Trapezoidal-Shaped Surface

This article describes a photonic crystal fiber (PCF) temperature sensor that utilizes a flat, metal-coated trapezoidal surface. The PCF is made up of two layers of elliptical air holes and a polished trapezoidal surface that allows temperature sensing. An external sensing approach is used to deposit a thin silver layer on the reflective surface, while a thin SiO2 film acts as an oxidation-resistant coating. The top elliptical air hole serves as the interface for energy transformation from the core-guided mode to the surface plasmon-polariton (SPP) mode. Simulations carried out using the finite element method indicate that the proposed SPR-PCF temperature sensor can achieve a maximum temperature sensitivity and resolution of up to 5200 pm/°C and 0.01923 °C, respectively, across a temperature range of 10 to 60 °C. This research has significant potential for sensor design and real-time temperature remote sensing applications.

Ultra-high birefringence mid-infrared Ge20Sb15Se65 chalcogenide glass photonic crystal fiber with low confinement loss

This study introduces a Ge20Sb15Se65 chalcogenide-glass-based photonic crystal fiber (PCF) with high birefringence and nonlinearity and ultra-low confinement loss, in which two elliptical air holes are added in the core. The propagation properties of the proposed PCF are investigated in mid-infrared range (3.0–5.0 μm) using the finite element method (FEM). Simulation results indicate that optimizing structural parameters can increase the birefringence and nonlinear coefficient to a maximum of 3.16 × 10−1 and 5937 W−1km−1 (in y-polarization mode), respectively, a significantly low confinement loss reach 10−14 dB m−1 at 3.0 μm wavelength, there can obtain one zero dispersion wavelength in the study band, and the designed structure can be fabricated using available technology. The designed PCF will have promising application in mid-infrared fiber fields, optical communication, super-continuum generation, precision, and nonlinear optics.

High birefringence single-polarization composite structured anti-resonant fiber

We propose a highly birefringent, single-polarization composite structured anti-resonant fiber (CS-ARF). The proposed CS-ARF has an elliptical core, two symmetrically spaced arrays of elliptical air holes, and a six-tube anti-resonant structure. The birefringence and single-polarization characteristics of the proposed CS-ARF were analyzed in detail in the mid-infrared band using the finite element analysis method. The results show that the fiber can achieve birefringence up to the order of 10−2 and single-polarization transmission with a confinement loss (CL) below 10−5 dB/m in the mid-infrared band. When the refractive index of the elliptical core is set at na = 2.70, the designed CS-ARF maintains single polarization in the range of 2.5 μm to 3.197 μm with an extinction ratio of up to 1.08 × 107. In addition, we found that by setting the refractive index of the elliptical core, the CL in the y-polarization direction can be effectively adjusted.

Design of elliptical photonic crystal fiber (E-PCF) for the transmission of 116 OAM channels across the S, C, L and U bands

Orbital angular momentum (OAM) modes over photonic crystal fibers (PCFs) have shown great capability in unleashing the available data rates in optical communication systems. In this paper, we propose and numerically design a novel elliptical photonic crystal fiber (E-PCF) using assisted Germania-doped silica as a material background and elliptical air holes. Using a systematic scanning methodology, we adjusted the E-PCF key parameters with the aim to explore appropriate designs that support large number of OAM channels featuring low confinement loss (CL). Numerical simulations using finite element method (FEM) show the supports of large number of independent/separate OAM channels (116 OAM with Δneff≥ 10−4). A detailed numerical modal analysis has been carried out over the S + C + L + U communication bands show that the designed E-PCF handles robust OAM modes. This includes low chromatic dispersion (CD = 92 ps/km/nm), low differential group delay (<60 ps/km), high effective mode area (max Aeff = 124 µm2), low nonlinearity coefficient (γ < 2.6 /W/m) and low confinement loss (Max CL = 2.07 × 10−4 dB/m). The obtained results and the comparisons with those recently reported in literature shows that the designed E-PCF could find applications in next-generation optical communication systems that uses OAM modes as data carriers.

Susceptible Plasmonic Photonic Crystal Fiber Sensor with Elliptical Air Holes and External-Flat Gold-Coated Surface

This paper proposes and analyzes a simple surface plasmon resonance (SPR)-based elliptical air hole photonic crystal fiber (PCF) sensor. The fiber structure comprises an analyte channel of the fiber surface coated with a gold layer on the flat surface and the fiber’s external surface. Numerical simulations are conducted using the finite element method (FEM) with an external sensing approach. We found that the thickness of plasmonic material (Au) is the most crucial factor that affects the full width at half maximum (FWHM) and confinement loss amplitude. We also demonstrated that the proposed elliptical air hole SPR-PCF is superior to circular air hole SPR-PCF in terms of confinement loss and FWHM. According to the wavelength interrogation technique, the simulation results show that the designed SPR-PCF sensor can attain a maximum sensitivity of 116,500 nm/RIU and a resolution of 8.58 × 10−7 RIU (RIU: refractive index unit) for the analyte RI of 1.395. We believe the proposed SPR-PCF sensor can be a potential candidate for biomolecular and biological analyte detection.

High coherent supercontinuum generation in nitrobenzene liquid-core photonic crystal fiber with elliptical air-hole inner ring

A nitrobenzene liquid-core photonic crystal fiber (NLC-PCF) with eight elliptical air-holes in the innermost ring of the cladding is proposed in this work, and this fiber structure can contribute to flexibly adjusting dispersion and constraining the fiber core. The appreciable dispersion is realized by adjusting the structural parameters of NLC-PCF, which is characterized by three zero-dispersion wavelengths (ZDWs), flat dispersion with the fluctuation of fewer than 40 ps nm−1 km−1, and high nonlinearity as high as 5500 W−1 km−1. The propagation of femtosecond pulse and supercontinuum generation (SCG) in NLC-PCF is studied numerically when the pump wavelength is located in the normal and abnormal dispersion region near different ZDW through solving the generalized nonlinear Schrödinger equation (GNLSE) by the split-step Fourier method. The numerical results show that a highly coherent supercontinuum (SC) spanning from 1.3 to 2.8 µm is obtained when the pump pulse with the center wavelength of 1810 nm, the peak power of 1000 W, and pulse width of 50 fs propagated in the 5 cm long NLC-PCF. This research can find applications in the fields of novel liquid-core PCF design and ultrashort pulse propagation.

A D-shaped elliptical hollow core fiber SPR sensor

A D-shaped elliptical hollow core fiber surface plasmon resonance (SPR) sensor is proposed and analyzed here using gold and titanium oxide (TiO2) layer. The fiber geometry consists of a doped elliptical core with a concentric central elliptical air hole. A finite element method-based simulation software COMSOL Multiphysics is used for numerical analysis. Both gold and TiO2 layers are optimized. The sensor responds over a wide range of refractive index (RI) from 1.33 to 1.40. The average sensitivity obtained for the designed sensor is 4142.85nm/RIU (RI Unit) whereas that for a single mode fiber (SMF) is only 897.55nm/RIU. So, our designed sensor gives more than 4 times enhanced sensitivity and proves to be a potential alternative of SMF based low cost, compatible SPR sensors by covering the low sensitivity issue suffered by SMF sensors.

A Novel Structured Magnetic Field Sensor Based on Photonic Crystal Fiber Filled with Magnetic Fluid

A novel structured magnetic field sensor based on dual-core photonic crystal fiber is proposed which has two elliptical central holes filled with magnetic fluid and some elliptical cladding air holes. The transmission characteristics of the dual-core photonic crystal fiber such as coupling length, birefringence, and coupling loss are analyzed with changing structural parameters. Enhanced birefringence is obtained by the novel structure of two elliptical central holes and some elliptical cladding air holes. The sensitivity of the magnetic sensor is calculated, and the numerical simulation result shows that the highest sensitivity of 1200 pm/Oe can be achieved.

Elliptical air hole PCF-based low-cost sensor for refractive index and temperature detection: Design and analysis

In a recent scenario, sensor technology is attractive and promising for industrial applications. The microstructure-based sensors are preferable due to their outstanding performance, compact size, fast response, accuracy, and wide range of availability. Photonic crystal fiber (PCF) fulfills the demand to develop such a sensor. This article proposed an elliptical air hole-based photonic crystal fiber (EH-PCF) with a circular ring at the core filled with platinum for temperature and refractive index sensing applications, simultaneously. The proposed design displays the mode field density of −8.86e-14 w/m at the core, and two transmittance dips of −88 dB are obtained at 1.53 µm and ∼1.56 µm wavelength after simulation results. One of the significant factors that affect the sensitivity of the sensor is mode confinement loss that is 6.5x104 dB/cm at 1.55 µm wavelength. The proposed sensor shows a sensitivity of 77 nm/°C for the temperature range of 20–160 °C and refractive index (RI) sensing in the range of 1.43 to 1.49 indicated the sensitivity of 1600 nm/RIU. Due to the complex RI, the ultranarrow bandgap is between the 0.10 to 0.11 frequency (w/2pic) for surface plasma resonance signals. The fabrication of the proposed design is a simple, low-cost method and will be significantly suitable for integrated photonics, nanotechnology, industry 4.0, temperature sensing, and biomedical applications.

Broadband birefringence hollow-core anti-resonant optical fiber with elliptical air holes

We present a novel hollow-core anti-resonant optical fiber (ARF) with nested elliptical and nested circular air holes, where these cladding air holes form into the elliptical core. The simulation results show the fiber has low loss, high birefringence, broadband, and bend-resistance properties by optimizing its structure parameters. Besides, it also exhibits that the fundamental mode (FM) losses of x-polarization and y-polarization, high birefringence, and broad transmission band are 0.03 dB/m, 0.043 dB/m, 1.33 × 10−4, 460 nm, respectively.

Panda-type elliptical-core fiber with flat and low normal-dispersion at 1.5–2.5 µm

The panda-type polarization-maintaining fiber (PMF) with a heavily GeO2-doped elliptical core is proposed for the supercontinuum generation. An elliptical air hole is introduced into the core to tailor the dispersion and birefringence properties. The proposed fiber with an appropriate choice of parameters can exhibit a flat and near-zero normal-dispersion profile at 1.5–2.5 µm, and its birefringence reaches beyond 8.8 × 10−4 due to the combined effects of the stress-applying parts (SAPs) and elliptical core with an air hole. The linearly polarized flattened supercontinuum extending over one octave can be generated when the 0.1-ps linear-polarization pulse with the peak power of 100 kW at 1920 nm is injected into a 1-m-long proposed fiber and polarized along the principal axes.

Numerical analysis of a photonic crystal fiber with elliptical air hole for supporting 80 orbital angular momentum modes

• We design photonic crystal fiber with elliptical air holes, which has good orbital angular momentum transmission performance. • The influence of elliptic air hole eccentricity on photonic crystal fiber transmission performance is analyzed. • This paper provides some ideas for new photonic crystal fiber design and air hole shape error analysis. In this paper, a new photonic crystal fiber with elliptical air hole (EAH-PCF) is designed, which can support stable transmission of 80 orbital angular momentum (OAM) modes at 1550 nm. The effective refractive index differences between vector modes are all above 0.002. Most of the modes have a confinement loss between 10 −10 dB/m and 10 −8 dB/m. The effective mode area of the vector modes are all greater than 70 μm 2 and the nonlinear coefficients are all less than 1.8 W −1 /km. These properties guarantee high quality OAM. Finally, we discuss the effect of EAH’s eccentricity on the PCF. Simulations show that increasing the EAH’s eccentricity will increase the degree of separation between the vector modes, but causes a slight decrease in the quality of OAM.

Research on novel single-mode polarization maintaining photonic crystal fiber

Abstract A PCF (photonic crystal fiber) with high birefringence and single-mode polarization retention over a wide wavelength range is designed and studied. The birefringence and polarization retention characteristics of the PCF base mode were studied using FVFEM (full vector finite element method) and APML (anisotropic perfect matching layer) as boundary conditions. The simulation results show that by rotating the elliptical air hole parallel to the horizontal axis by 45°, and then rotating the elliptical air hole parallel to the longitudinal axis by 45°, the birefringence of the PCF obtained is as high as 4.7 × 10−2, and it has good single model ability, which can be used for various optical devices.

Ultra-slow light with high normalized delay–bandwidth product and refractive-index sensing in photonic crystal coupled-cavity waveguide

Ultra-slow light can enhance light–matter interactions and effectively realize all-optical buffering and modulation. In this paper, we present an efficient design for a two-dimensional square-lattice photonic crystal coupled-cavity waveguide, which can realize multi-frequency band slow-light transmission in the near-infrared band (1500–1640 nm).Through adjusting intercavity spacing N and structural parameters of elliptical air holes, high group index ng (202.46) within the bandwidth of 5.04 nm and improved normalized delay–bandwidth​ product of 0.6583 can be obtained at the wavelength of 1550.05 nm. Moreover, the designed devices can effectively function as a slow light sensor with the wavelength sensitivity of 585 nm/RIU. Multiple functions can be achieved synchronously in only one structure, which is essential in complex optical integrated circuits.

Simulation of Amorphous Silicon Carbide Photonic Crystal Absorption Layer for Solar Cells

In this work, the amorphous silicon carbide (a-SiC) with low cost and high extinction coefficient was used as the light absorption layer of solar cells, and the photonic crystal (PC) structure and defect structure were introduced. By optimizing the scatterer shape, structural parameters and defect types of photonic crystal, the absorption efficiency of the light absorption layer was further improved. The results show that the photonic crystal absorption layer with vacancy line defect is better than the perfect photonic crystal absorption layer. Meanwhile, the absorption efficiency of the photonic crystal absorption layer significantly improves in the case that the scatterer is an elliptical cylindrical air hole scatterer. When the incident light is in the wavelength range of 0.30~0.80 μm and the absorption layer height is 0.60 μm, the absorption efficiency of the absorption layer can reach 95.60%. Compared with the absorption layer without photonic crystal structure, the absorption layer is increased by 43.24%. At the same time, the absorption layer has little dependence on the incidence angle of sunlight. When the incidence angle is 65°, the absorption efficiency is still higher than 80%.

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.

Broadband Birefringence Hollow-Core Anti-Resonant Optical Fiber with Elliptical Air Holes

Broadband Birefringence Hollow-Core Anti-Resonant Optical Fiber with Elliptical Air Holes