Air Holes In Cladding Research Articles

Photonic crystal fibre optic sensor based on a U-shaped detection channel with large air-hole cladding

A photonic crystal fibre-optic sensor based on a U-shaped detection channel with a large aperture cladding has been designed for refractive index sensing and detection, taking advantage of the flexibility of the photonic crystal fibre-optic structure and its superior performance. The results show that the relative intensities and central wavelengths of the directional coupling absorption peaks of the photonic crystal fibre-optic sensor are closely related to the ratio of the long and short semi-axes of the U-shaped detection channel and the thickness of the gold nanofilm. The sensor has a sensitivity of up to 21700 nm/RIU in the refractive index range of 1.33–1.43, a resolution of 4.608 × 10−6 RIU and a maximum quality factor of 126.12 RIU−1. Photonic crystal fibre-optic sensors with large-aperture cladding and U-shaped detection channels are simple in structure, highly sensitive and have significant potential applications in environmental monitoring, medical assays and industrial control.

Detection of different drinkable milk using photonic crystal fibre biosensor in IR regime

A simplified PCF sensor has been designed to detect the different drinkable milk that includes camel, cow and buffalo milk, and can also assess its quality. The sensor features a singular circular core design and two layers octagonal cladding air holes that was analysed using the Finite Element Method technique in COMSOL Multiphysics software and determine the sensing and optical performance parameters: power fraction, relative sensitivity, confinement loss, effective area, numerical aperture, V-Parameter, spot size, and beam divergence. At the optimum wavelength of 6.0 μm, the relative sensitivities are 96.58%, 96.78%, and 96.84%, and confinement losses of 3.51 × 10−8 dB/m, 1.47 × 10−8 dB m−1, and 8.59 × 10−9 dB/m, for camel, cow, and buffalo milk, respectively. The efficacy of the proposed PCF structure for sensing applications in the dairy industry in distinguishing between different types of milk is evidenced by these findings. Moreover, the results of confinement loss and chromatic dispersion suggest potential applications of this design in optical communication.

3D soft glass printing of preforms for microstructured optical fibers

We report on the development of a 3D printing process dedicated to the production of soft glass optical fibers. Direct printing with a miniaturized crucible for melting glass blocks with a pneumatic extrusion head was established. For 3D printing, a developed in-house heavy metal oxide glass was used. Contrary to previous studies on 3D printing of optical fiber preforms, the proposed process is based on the deposition of straight horizontally-oriented lines with a diameter of 300–500 µm to replace standard stack-and-draw manual assembly technique typically used in the development of microstructured optical fiber preforms. A test fiber preform composed of 2500 microrods with dimensions of 60x25x25 mm was printed. As a proof of concept, a photonic crystal fiber preform composed of a solid core and 3 rings of air holes in photonic crystal cladding was printed, and further processed into the optical fiber using a standard fiber drawing tower. We measured a single mode performance of fabricated fibers at 1.55 µm, and flat dispersion in the range of 1.6 – 2.2 µm with zero dispersion wavelength at 1.70 µm.

Performance evaluation of photonic crystal fibre sensor for controlled drugs detection: a simulation approach

This study proposes a simple and efficient Photonic Crystal Fibre sensor design for the detection of controlled drugs such as cocaine, amphetamine, and ketamine. The design uses a pentagonal core hole and circular cladding air holes in 2 layers, made of fused silica substrate. The sensing performance of the proposed PCF design is evaluated using COMSOL Multiphysics and Finite Element Method, operating in the visible and infrared range from 0.4 to 3.2 μm. Results show that the proposed PCF design achieves high relative sensitivities of 99.55%, 99.75%, and 99.99% for cocaine, amphetamine, and ketamine, respectively, at the optimum wavelength of 0.4 μm. Additionally, the design is robust, showcasing minimal variations in relative sensitivities with changes in pitch distance, air hole diameter, and core hole length. These findings make the proposed PCF design a promising candidate for practical controlled drug sensing.

Residual dispersion compensation photonic crystal fiber based on simulated annealing algorithm and Livelink data interaction

An octagonal photonic crystal fiber (O-PCF) structure with equal air hole diameter of the cladding is proposed for residual dispersion compensation, and a high refractive index material SF57 is introduced in the core region to make it have the advantages of high negative dispersion, low attenuation loss, low fabrication difficulty. Due to the symmetric structure, no additional polarization control is required in the dispersion compensation process, which further reduces the production cost. Using Livelink data interaction not only accelerates the modeling of O-PCF, but also enables the effective refractive index of HE11 to be unattended continuously searched. Furthermore, simulated annealing algorithm is used to reverse design the structural parameters of cladding air hole diameter and central solid hole diameter. The results show that, based on the simulated annealing algorithm interacting with Livelink data, the optimize efficiency, design accuracy and dispersion characteristics are improved. The ultra-flat high negative dispersion O-PCF can be reverse designed in the S + C + L and S + C + L + U bands which shows the average dispersion of −847.34 ps/(nm·km) and −752.90 ps/(nm·km) with the absolute dispersion of only ±7.25 ps/(nm·km) and ±10.28 ps/(nm·km), respectively. The designed RDCF is tolerant to ±1% and ±2% variation of the central solid hole diameter and the cladding air hole diameter during fabrication, respectively. The combination of simulated annealing algorithm and Livelink data interaction provides an efficient method for reverse design of PCF.

Analysis of a photonic crystal fiber with ellipse air-holes for supporting 82 orbital angular momentum modes

We proposed a photonic crystal fiber (PCF) with ellipse air holes and high refractive index ring-core, which can stably support 82 orbital angular momentum states from the wavelength of 1.25–1.65 μm. The modes’ average confinement loss keeps as low as 10−9 dB m−1. In addition, the effective refractive index separation (Δn eff) between HE m +1,1 and EH m −1,1 (m = 2–21) is up to 10−3, which makes the mode degeneracy to LP mode can be almost neglected. The dispersion curves of low order eigenmodes are low and flat, especially at the wavelength of 1.4 μm the minimum absolute value of chromatic dispersion for HE1,1 mode is as low as 0.246 ps (nm·km)−1. Furthermore, we also analyze the effect of ellipticity change on the cladding air holes, which instructively show the favorable fault tolerance of confinement loss and dispersion. The proposed PCF structure will be a potential candidate for high-capacity optical fiber communications.

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.

A gold film coated dual-core photonic crystal fiber for refractive index and temperature sensing with high isolation

• When measuring RI of an analyte, the measurement is often affected by temperature. the simultaneous measurement of RI and temperature has important significance. • In this paper, a gold film coated dual-core photonic crystal fiber (DC-PCF) was proposed and numerically investigated for both RI and temperature sensing. • The maximum sensitivity of the RI reached 8100 nm/RIU, while the maximum sensitivity of temperature reached 1.3 nm/°C. • The design of dual independent cores in DC-PCF not only avoids the problem of cross-sensitivity; but also improves the isolation of the sensor. When measuring the refractive index (RI) of an analyte, the measurement is often affected by temperature. Therefore, the simultaneous measurement of RI and temperature has important research significance. In this paper, a gold film coated dual-core photonic crystal fiber (DC-PCF) was proposed and numerically investigated for both RI and temperature sensing. In order to stimulate the surface plasmon resonance (SPR) with high sensitivity to the surrounding, two gold films were coated on the polished surface and inner wall of a cladding air hole in the DC-PCF, respectively. Numerical results showed that the measurement sensitivities of RI and temperature reached 8100 nm/RIU based on Core I and 1.3 nm/°C based on Core II, respectively. It should also be noted that the designed sensor showed a high isolation. This designed sensor can be used where the RI of analyte should be detected at a high temperature accuracy.

Transmission performance of multimode W-type microstructured polymer optical fibers.

By solving the time-independent power flow equation (TI PFE), we study mode coupling in a multimode W-type microstructured polymer optical fiber (mPOF) with a solid-core. The multimode W-type mPOF is created by modifying the cladding layer and reducing the core of a multimode singly clad (SC) mPOF. For such optical fiber, the angular power distributions, the length Lc at which an equilibrium mode distribution (EMD) is achieved, and the length zs for establishing a steady state distribution (SSD) are determined for various arrangements of the inner cladding's air-holes and different launch excitations. This information is useful for the implement of multimode W-type mPOFs in telecommunications and optical fiber sensors.

Design and simulation of heptagonal porous core photonic crystal fiber for terahertz wave transmission

A heptagonal core and hexagonal cladding Porous Core Photonic Crystal Fiber (PC-PCF) is proposed for terahertz wave guidance. Important transmission properties including confinement loss, effective material loss (EML), and core power fraction are investigated by using the Finite Element Method (FEM) in COMSOL Multiphysics simulation software. At an operating frequency of 1 THz and a carefully selected optimum parameter set, the proposed fiber shows confinement loss in the order of 10−4 dB/m, relative material absorption loss of 0.04 cm−1, and core power fraction of 45%. Guidance properties such as effective area, bending loss, and dispersion are also investigated in detail. Due to the simple design of circular air holes in both core and cladding, the PC-PCF is envisaged to be fabricated using the available stack and draw method. The proposed fiber is envisaged serve as an efficient waveguide for transmitting terahertz wave, particularly in communication applications due to its small loss and dispersion.

A Multi-Parameter Integrated Sensor Based on Selectively Filled D-Shaped Photonic Crystal Fiber.

We propose and numerically investigate a multi-parameter integrated sensor based on a selectively filled D-shaped photonic crystal fiber (PCF). The simple structure can be used to comprehensively detect refractive index, magnetic field, temperature, and voltage. According to the surface plasmon resonance and directional coupling effect, the PCF is coated with a gold nano-film to detect the refractive index of the external environment. In addition, magnetic fluid (water-based Fe3O4), toluene, and nematic liquid crystal (NLC E7) are selectively filled into different cladding air holes of the D-shaped PCF to realize the different sensing of the magnetic field, temperature, and voltage. The measurement of refractive index, magnetic field, temperature, and voltage are independent of each other, so these four parameters can be measured simultaneously. The sensing characteristics of the proposed structure are investigated systematically by the finite element method. The results show that the sensitivities of refractive index, magnetic field, temperature, and voltage are 4600 nm/RIU, 1.375 nm/Oe, 15.143 nm/°C, and 0.971 nm/V, respectively. The presented design based on materials selectively filled with D-shaped PCF might enable promising application in multi-parameter optical sensing.

A heptagonal PCF-based oil sensor to detect fuel adulteration using terahertz spectrum

A heptagonal photonic crystal fiber-based oil sensor is proposed and numerically investigated in this paper in order to detect the adulteration of petrol with kerosene using terahertz (THz) signal. The sensing and guiding properties of this sensor is analyzed by using the Finite Element Method (FEM) technique. The sensor achieved a high relative sensitivity of 96.87% with an extremely low loss of 7.21 × 10−4 cm−1 at optimum frequency and structural conditions which outstripped other existing researches. In addition, the sensor offers a small effective material loss of 0.0072 cm−1 with high numerical aperture and spot size. The four layers circular air holes of heptagonal cladding with a large circular-shaped core are represented in this study which reduces fabrication complexity. This outstanding sensitivity and guiding properties might play a vital role in fuel adulteration identification applications in the near future.

Highly sensitive SPR-based PCF bio sensor for plasma cell detection in human blood for the detection of early stage cancer

This study investigates an extremely sensitive surface plasmon resonance (SPR)-based Photonic crystal fiber (PCF) biosensor to detect blood plasma cell. A blood sample is put into one of the PCF cladding's air holes. This results in a substantial confinement loss which is used to study as the analyte core mode, while the background is used as the silica mode. To induce plasmonic effects, the plasma sample is injected into one of the air holes in the PCF cladding and its outer covering is coated with Indium Tin Oxide (ITO). In the range of 1.3246–1.3634 for the analyte refractive index, this determination of plasma yielded a sensitivity of 6701.03 nm/RIU for x-polarization and 5154.63 nm/RIU for y-polarization. The provided sensor's sensing output is investigated by using Finite Element Method (FEM)-based programme with a detection limit of 0.0097 RIU overall. Using the analyte defect layer with varied refractive indices, we were able to generate a difference in the resonant peak positions. As a result of our simulation results, it is vital to highlight that the suggested sensor exhibits notable sensor performance for both polarization modes, allowing for more frequent light source selection during practical implementation. Our proposed sensor can detect organic chemicals, biochemical analytes, and can also be used extensively in medical diagnostics, according to the findings.

A highly sensitive sensor of methane and hydrogen in tellurite photonic crystal fiber based on four-wave mixing

A tellurite photonic crystal fiber (PCF) sensor structure is proposed for simultaneous measurements of methane and hydrogen. The structure is a simple hexagonal three-cladding structure, and six air holes in the inner cladding are coated with methane sensitive film and hydrogen sensitive film respectively. Based on the degenerate four-wave mixing (DFWM) theory, the direct relationship between the wavelength shifts of the Stokes spectrum or anti-Stokes spectrum and the variations in gas concentration can be established to realize the accurate detection of gas concentration. The influences of the pump wavelength and gas-sensitive film thickness on the gas sensitivity are investigated, and the maximum sensitivities of methane and hydrogen after parameter optimization are − 2.052 nm/% and − 0.236 nm/%, respectively. The linearity of the fitting can reach up to 99.95%, and the low detection limit of methane is 450 ppm and hydrogen is 2500 ppm. The sensing method based on four-wave mixing in non-silica photonic crystal fiber can also be extended to other detections of gas mixtures in the mid-infrared field.

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.

High sensitivity dual core photonic crystal fiber sensor for simultaneous detection of two samples

The optical control ability of photonic crystal fiber (PCF) is a distinctive property suitable for improving sensing and plasma performance. This article proposes a dual-core D-channel PCF sensor that can detect two samples simultaneously, which effectively solves the problems of coating difficulty and low wavelength sensitivity. The PCF has four layers of air holes, which dramatically reduces the optical fiber loss and is more conducive to the application of sensors in actual production. In addition, by introducing dual cores on the upper and lower sides of the central air hole, reducing the spacing between the core and the gold nanolayer, a stronger evanescent field can be generated in the cladding air hole. The optical fiber sensor can detect the refractive index of two samples simultaneously with a maximum sensitivity of 21300 nm/RIU. To the best of our knowledge, the sensitivity achieved in this work is the highest sensitivity with the dual sample synchronous detection sensors. The detection range of the refraction index is 1.35–1.41, and the resolution of the sensor is 4.695 × 10−6. Overall, the sensor will be suitable for medical detection, organic chemical sensing, analyte detection, and other fields.

Numerical investigation of gold plated single-core photonic crystal fiber-based refractive index sensor

Surface plasmon resonance (SPR)-based single-core photonic crystal fiber (PCF) biosensor is investigated with external gold coating. All the geometrical parameters such as a gold layer, an analyte layer, a lattice period and cladding air holes are optimized to enhance the sensing ability of the sensor by introducing the finite element method. The designed sensor is able to achieve the highest amplitude sensitivity (AS) of 2258.95 RIU[Formula: see text] with an acceptable refractive index sensitivity (RIS) of 6000 nm/RIU over the analyte refractive index (ARI) span of 1.31–1.40. This sensor can detect a slight index alteration in the sensing medium using a resolution of [Formula: see text] and a high figure of merit (FOM) of 79.01. With the enhanced modal behavior with simple geometry, the resulting sensor can be suitable for real-time monitoring in biological, biochemical and bio-imaging applications.

Theoretical Investigation of Mid Infrared Temperature Sensor Based on Sagnac Interferometer Using Chloroform Filled Photonic Crystal Fiber

In this paper, a novel Sagnac Interferometer (SI) based chalcogenide Photonic Crystal Fiber (PCF) temperature sensor is theoretically and numerically analyzed operating in the mid infrared (MIR) region. The PCF cladding air holes are proposed to be filled with a highly temperature sensitive liquid chloroform to enhance the temperature sensitivity. The temperature sensing characteristics of three different infiltration technique is investigated theoretically and compared by Finite Element Method (FEM). Simulation results show that full infiltration performs better than partial infiltration. In the numerical analysis two sensing dips with high linearity is achieved for full infiltration which shows sensitivity of −5.77 nm/°C and 8.49 nm/°C when the temperature increases from 25 to 85 °C for the specific fiber length of 1.532 mm. The R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> values are 0.957446809 and 0.97680771 for the respective two sensing dips. The proposed highly sensitive sensor has broad detection window which can be applied in fingerprint unlocking, MIR radiation detection in human body, biomedicine applications, and environmental temperature monitoring.

Design of a mid-infrared single-mode laser based on parity-time symmetry breaking in air-clad hollow-core ZBLAN fiber micro-resonator

In this paper, we propose a single-mode laser operating in the mid-infrared regime by exploiting parity-time (PT) breaking in a whispering gallery mode (WGM) micro-resonator based on air-clad hollow-core ZBLAN fibers. By introducing alternate gain–loss modulation regions with refractive indices respectively having the same real parts but opposite imaginary parts into the air hole clad region of the hollow-core fiber infiltrated with optical functional materials, a PT symmetry system could be set up and specific WGM in PT-broken state whose electric field distribution matches the gain–loss modulation pattern can be excited to realize single-mode laser emission around 5 μm. And moreover, simulation results indicate that high precision laser wavelength tuning with a sensitivity of 1.623 nm RIU−1 can be achieved by adjusting the refractive index of the functional materials filled into the cladding air holes.

Thermal stability analysis of polarization-maintaining photonic crystal fibers in bending state

In this paper, polarization-maintaining photonic crystal fibers (PM-PCFs) with odd-edge and even-edge arrangements of air holes in cladding, such as pentagon, hexagon, heptagon, and octagon, were taken as the research objects. The temperature characteristics of birefringence and loss of fibers with different structures in the bending state were compared and analyzed. The results show that the PM-PCFs with the cladding air holes odd-edge distributed have better thermal stability, especially the fiber with the pentagonal distribution of cladding air holes. This research provides a theoretical reference for selecting optical fibers and designing methods for photonic crystal fiber applications that require high output performance stability