Circular Air Holes Research Articles

High-Sensitivity Refractive Index Sensor with Dual-Channel Based on Surface Plasmon Resonance Photonic Crystal Fiber.

In order to achieve a high-precision synchronous detection of two different refractive index (RI) analytes, a D-type surface plasmon resonance (SPR) photonic crystal fiber (PCF) RI sensor based on two channels is designed in this paper. The sensor uses a D-shaped planar region of the PCF and a large circular air hole below the core as the sensing channels. Surface plasmon resonance is induced by applying a coating of gold film on the surface. The full-vector finite-element method (FEM) is used to optimize the structural parameters of the optical fiber, and the sensing characteristics are studied, including wavelength sensitivity, RI resolution, full width at half maximum (FWHM), figure of merit (FOM), and signal-to-noise ratio (SNR). The results show that the channel 1 (Ch 1) can achieve RI detection of 1.36-1.39 in the wavelength range of 1500-2600 nm, and the channel 2 (Ch 2) can achieve RI detection of 1.46-1.57 in the wavelength range of 2100-3000 nm. The two sensing channels can detect independently or simultaneously measure two analytes with different RIs. The maximum wavelength sensitivity of the sensor can reach 30,000 nm/RIU in Channel 1 and 9900 nm/RIU in Channel 2. The RI resolutions of the two channels are 3.54 × 10-6 RIU and 10.88 × 10-6 RIU, respectively. Therefore, the sensor realizes dual-channel high- and low-RI synchronous detection in the ultra-long wavelength band from near-infrared to mid-infrared and achieves an ultra-wide RI detection range and ultra-high wavelength sensitivity. The sensor has a wide application prospect in the fields of chemical detection, biomedical sensing, and water environment monitoring.

PCF Based Four-Channel SPR Biosensor With Wide Sensing Range.

In this article, we have demonstrated a highly sensitive four-channel photonic crystal fiber (PCF) based surface plasmon resonance (SPR) biosensor which can detect four different analytes simultaneously. To ease practical implementation, four analyte sensing layers and plasmonic materials such as gold (Au) and gold (Au) with Tantalum Pentoxide (Ta2O5) are placed on the exterior of the four arms of the square shaped structure. The sensor's structure consists of only nine circular air holes, making it simple and easy to fabricate using currently available technologies. Finite element method (FEM) based numerical analysis is used to evaluate the sensing performance of the proposed sensor. With optimum structure parameters, the sensor achieves maximum wavelength sensitivity of 11000, 25000, 11000 and 25000 nm/RIU for Channel-1, Channel-2, Channel-3, and Channel-4 respectively. It shows maximum amplitude sensitivity of 803.732, 709.171, 803.827, 709.146 RIU -1 for Channel 1, 2, 3, and 4 respectively. It also shows maximum FOM of 232.55, 352.36, 231.57, 352.36 RIU -1 in Ch-1, Ch-2, Ch-3 and Ch-4 respectively. Moreover, the proposed sensor shows a wide range of refractive index sensing capability from 1.30 to 1.41. Due to multi-analyte detection capability, large sensing range, and excellent sensitivity the proposed sensor unfolds unrivalled capacity of detecting chemicals, carcinogenic agents, biomolecules, and other analytes.

Investigation on photonic crystal nanobeam cavity based on mixed diamond–circular holes

A photonic crystal nanobeam cavity (M-PCNC) with a structure incorporating a mixture of diamond-shaped and circular air holes is proposed. The performance of the cavity is simulated and studied theoretically. Using the finite-difference time-domain method, the parameters of the M-PCNC, including cavity thickness and width, lattice constant, and radii and numbers of holes, are optimized, with the quality factor Q and mode volume Vm as performance indicators. Mutual modulation of the lattice constant and hole radius enable the proposed M-PCNC to realize outstanding performance. The optimized cavity possesses a high quality factor Q = 1.45 × 105 and an ultra-small mode volume Vm = 0.01(λ/n) [Zeng et al., Opt Lett 2023:48;3981–3984] in the telecommunications wavelength range. Light can be progressively squeezed in both the propagation direction and the perpendicular in-plane direction by a series of interlocked anti-slots and slots in the diamond-shaped hole structure. Thereby, the energy can be confined within a small mode volume to achieve an ultra-high Q/Vm ratio.

Design and performance analysis of PCF-based octagonal chemical sensor to detect benzene, ethanol, and water in terahertz spectrum

An octagonal cladding with a hexahedron core PCF sensor is designed to detect chemical compounds at terahertz frequency. The proposed sensor contains circular air holes (CAHs) in the vestibule area. To measure the performance of the sensor effective material loss, confinement loss, and a large frequency area have been used in terms of relative sensitivity (RS). For the design and analysis of our proposed hexahedron PCF sensors, the finite element (FEM) utilizes numerally the optic parameters. The diameter and core size of the proposed air whole were checked to optimize the production tolerance and sensing performance. At the area of 1 THz spectrum Ethanol, Benzene, and Water are used for numerical examination The fiber appears to be a high Relative sensitivity which is 91.25 %, 93.80 %, and 89.95 % respectively for Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330). The sensor provides low confinement losses with 5.95 × 10−08 dB/m, 6.25 × 10−08 dB/m, and 5.94 × 10−08 dB/m corresponding for those three chemicals. The geometric construction of the projected sensor can be used in chemical sensing in biomedical, industrial quality control, material research, clinics, gas sensors, micro-optics, and many communication applications in THz technology.

Design and performance analysis of alcohols sensing using photonic crystal fiber in terahertz spectrum

This research suggests an optical sensor to detect alcohol in beverages and liquids that is based on Zeonex backdrop material. The core of the sensor is made up of six hexahedron-shaped cores and heptagonal cladding with circular air holes. The development and implementation of a limited element evaluation to assess the sensing capabilities of sensor technology using PCF were executed using the COMSOL Multiphysics software. With negligible confinement losses, a highly sensitive H-PCF structure has been proposed for the THz range. With sensitivities of 89.50 %, 91.80 %, and 90.81 %, respectively, at the monitoring region of 1 THz, it can detect three distinct alcohols, including ethanol, butanol, and propanol. At a monitoring frequency of 1 THz, the confinement losses for the first alcohol are 5.45 × 10−08 dB/m, the second alcohol is 6.01 × 10−08 dB/m, and the third alcohol is 5.60 × 10−08 dB/m. Furthermore, the essential graphical representations of additional optical properties, including the effective mode index, effective area, and total power fraction, are extensively examined. Thus, it is evident that this sensor could be utilized to detect alcohol in a variety of environments, given that terahertz (THz) wave pulses are commonly employed in both chemical processes and the food and beverage industries.

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.

An asymmetric slotted structured twin core photonic crystal fiber based highly sensitive surface plasmon resonance refractive index biosensor

A butterfly-shaped core photonic crystal fibers with less asymmetric rectangular and circular air holes are proposed, and their properties are numerically analyzed. The sensor construction is reduced to only seven air holes and uses surface plasmons stimulated inside gold (Au) strips for simplicity in manufacture and high sensitivity. Gold is employed as an effective plasmonic metal throughout this design to create resonant effects and is located away from the proposed structure to make production easier. Maximum amplitude sensitivity for the proposed sensor is 228.89 RIU−1, maximum wavelength sensitivity is 88,000 nm/RIU, and maximum wavelength resolution is 1.14 × 10−6RIU−1 for y-polarized mode where the figure of merit is 65.78 RIU−1 with a linearity of 0.9905. The proposed sensor can detect the RI of unspecified analytes between 1.27 and 1.40, allowing for the analysis of many different types of analytes, such as viruses, cancer cells, sugars, proteins, DNA/RNA and many more.

Design of Quasi-Shaped spectroscopy based optical sensor for the detection of alcohol

In this research, an entirely novel optical sensor for alcohol detection based on quasi-shaped spectroscopy is offered. A quasi shape with a tightly bonded structure in the cladding region and a hexahedron core region makes up the recommended design, which has a remarkable sensitivity of about 91.35%, 92.55%, and 90.40%and low confinement losses (CLs) of 5.44 × 10−08 dB/m, 6.75 × 10−08 dB/m, and 5.85 × 10−08 dB/m for detecting alcohol like ethanol (n = 1.354), butanol (n = 1.3993), and propanol(n = 1.384), at 1 THz. The numerical aperture, the effective area, and the V-parameter have all been identified and assessed. The 0.8THz to 3 THz operational wavelength range is stated. In the COMSOL Multiphysics (Version 5.6) environment, the properties of these suggested alcohol sensors are numerically examined utilizing the FEM (finite element method) with full vectors. In contrast to other efforts, the proposed sensor, which consists of a quasi-lattice PCF with a perfectly matched layer (PML) of a circular air hole shape and TOPAS as the background material, aims to improve sensitivity response. The proposed sensor might be crucial in the alcohol detection process due to its superior sensitivity response, a single mode of operation across the entire operational terahertz range, and shallow confinement loss. So, this PCF can proficiently be pragmatic in many biological sensing and other THz technology domains.

Design and numerical analysis of a novel photonic crystal fiber based chemicals sensor in the THz regime

We presented a decagonal cladding and hexahedron core-based photonic crystal fiber (PCF) to sense chemicals in the terahertz frequency (THz). Circular air holes (CAHs) in the cladding region make up the proposed sensor. A wide variety of frequencies were evaluated to analyze the sensor's performance in terms of sensitivity, confinement loss, and effective material loss respectively. We designed and quantitatively analyzed the optical properties of our proposed hexahedron-based PCF sensor using the finite element method (FEM). Square-shaped air hole length, strut, and core size have also been researched to improve the performance of the proposed sensor's sensing components and fabrication tolerance. At ideal conditions, the suggested PCF sensor has a maximum relative sensitivity of 94.65%, confinement loss of 6.01 × 10−8 cm−1, effective material loss (EML) of 9.16 × 10−4 cm−1, and effective mode area (EMA) of 1.35 × 10−7 m2. We are confident that the suggested sensor's optimized geometrical structure will be manufacturing-friendly, as well as the sensor's contribution to practical uses. Furthermore, our proposed PCF fiber will be ideal in the terahertz (THz) regions for various optical communication applications and medicinal signals.

Photonic crystal fibre for blood components sensing

A photonic crystal fibre (PCF)-based sensor has been proposed and thoroughly investigated for the identification of blood components, including red blood cells, haemoglobin, white blood cells, plasma, and water. To evaluate the sensor's sensing and propagation properties, a numerical analysis was performed using the COMSOL Multiphysics software. The proposed sensor design features an octagonal core and two layers of cladding with octagonal and circular air holes. At the optimal wavelength of 7.0 μm, the extensive simulation results confirms that the proposed sensor achieves high relative sensitivity of 99.89%, 99.13%, 97.95%, 97.77%, and 96.68% for red blood cells, haemoglobin, white blood cells, plasma, and water, respectively. Furthermore, the design demonstrates favourable confinement loss, propagation constant, V-parameter, spot size, and beam divergence. Therefore, the proposed PCF-based sensor holds great promise not only for medical sensing applications but also for optical communications. Its advanced design and highly sensitive capabilities make it a valuable tool for a wide range of potential applications in the biomedical and telecommunications fields.

A Highly Birefringent Photonic Crystal Fiber with Three Rows of Circular Air Holes

An exceptionally high-performance, high-birefringent photonic crystal fiber (PCF) is meticulously designed. The core design features a unique arrangement in which the central row of circular air holes is substituted by three rows of smaller circular holes. Subsequently, the middle row is adjusted to achieve various rectangular mode field configurations. With the optimized structure parameters, the birefringence of the PCF can reach 3.57 × 10−2 at a wavelength of 1.55 μm. The confinement loss is as low as 8.4 × 10−6 dB/m. The nonlinear coefficient is up to 41 W−1·km−1. The dispersion is relatively flat within the range from 1.3 μm to 1.9 μm. These remarkable characteristics render the proposed PCF a strong candidate for applications in polarization preservation, dispersion compensation, wideband supercontinuum generation, and other related fields.

Ultra-fast all-optical 8-to-3 encoder utilizing photonic crystal fiber

This work proposes a novel design of an 8-to-3 encoder in a photonic crystal fiber (PCF). It is composed of a buffer and three OR logic gates using circular air holes in a silicon dioxide substrate. We have employed the plane-wave expansion technique to analyze the band structure of the proposed PCF and the beam propagation method to study the transmission efficiency and electromagnetic field distributions. Our findings reveal that the encoder operates well within the main third telecommunication window, which corresponds to 1530–1565 nm. The numerical calculations show that transmissions greater than 70% and less than 0.05% are logics 1 and 0, respectively. The proposed encoder has a maximum delay of 7.5 ps, and its total footprint is about 140 µm × 14 µm × 3 mm. This makes the proposed PCF-based encoder suitable for simple and low-cost fabrication, which may find applications in optical communication devices and integrated circuits.

Inverse Design of Terahertz Optical Power Splitters Using the Particle Swarm Optimization Method

This letter proposes 50:50 TE terahertz power splitters based on digitized metamaterials. The components are optimized using the particle swarm optimization algorithm. The digitized metamaterials are formed as a silicon slab with circular air holes atop a silicon dioxide substrate. The insertion losses of optimized structures containing air holes with a radius of 9 μm and air holes with different radii (9 μm and 7 μm) are less than 3.9 dB and 3.65 dB, respectively, over a frequency range of 0.87–1.09 THz. The footprint of the proposed devices is 400 μm × 350 μm. The devices have excellent characteristics, such as compactness, efficiency, all-dielectric properties, and compatibility with CMOS fabrication technologies, and can become vital components of most terahertz-wave routing circuits.

Analytical approach for modeling and simulation of photonic crystal fiber based on low effective material loss

COMSOL Multiphysics simulation software has been used to create a hexagonal photonic crystal fiber (H-PCF) with hexagonal cladding and a rotating hexa elliptical shape core. The hexagonal photonic crystal fiber (H-PCF) fiber is built on five layers of circular air holes, and it is suitable for telecommunication applications especially optical fiber communication in the terahertz (THz) frequency range. The hexagonal photonic crystal fiber (H-PCF) is designed to have an ultra-low effective material loss (EML), a higher core power fraction, a bigger effective area, and reduced confinement loss. The smallest effective material loss from the proposed hexagonal photonic crystal fiber (H-PCF) is 0.00689 cm−1, with a better core power fraction of 82%, less confinement loss of 3.45 × 10–14 cm−1 and a better effective area of 3.65 × 10–4 m2 is achieved at one terahertz (THz) waveguide region. Furthermore, using the features of the V-Parameter, our developed hexagonal photonic crystal fiber (H-PCF) fiber reveals an optical waveguide with one mode throughout a frequency range of terahertz (THz) wave area. So, it has been said that our hexagonal photonic crystal fiber (H-PCF) structure will be highly beneficial for optical fiber communications applications in the THz frequency range.

Terahertz Wave Propagation Characteristics in Graded Teflon Based Solid-Core Photonic Crystal Fibre

In the past few years, photonic crystal fibre (PCF) in the Terahertz spectrum is drawing significant attention because of its multifaceted applications in high-speed data communication, spectroscopy, sensing, etc. The proposed PCF structure is based on a Teflon solid core surrounded by porous cladding. Teflon has been used as a background material because of its high flexibility and the possibility of making longer PCFs, which is capable of guiding waves in the THz region. The porous cladding consists of circular air-holes positioned hexagonally whose diameters increase with each subsequent layer keeping the pitch constant thus providing a graded-index profile. The diameters of air holes in each hexagonal layer are 1 mm, 1.2 mm and 1.5 mm respectively, maintaining a constant pitch of 2mm and a perfectly matched layer (PML) thickness of 3mm. We have examined the transmission characteristics of the proposed profile in the frequency range of 0.8 THz to 2.5 THz. The modal solution of the profile is solved using the Finite Element Method based on COMSOL Multiphysics version 5.5. Using the graded-index profile, we have obtained a large effective modal area of around 5.6 mm2 at 1 THz and a low confinement loss of 2.25 × 10−4 dB/km at the same frequency. Due to this large effective modal area, we get higher damage threshold and weaker non-linear effects, making it suitable for high power applications.

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.

A novel plasmonic sensor using solid core D-shaped negative curvature optical fiber with AU–TiO2 layer

Recently, unique structure fiber enacts a significant role in sensing applications. A novel D-shaped negative curvature fiber based surface plasmon resonance (SPR) sensor is proposed. The design consists of negative curvature solid core fiber surrounded by a cladding composed of double-layer adjoined airholes. An outside layer of the cladding contains semi-circular airholes, and the interior layer has small circular air holes to overwhelm the higher-order modes. The external sensing approach detects changes in the refractive index between 1.33 and 1.37. Employing gold as a plasmonic material, SPR is developed on top of the photonic crystal fiber (PCF). Between the gold layer and the PCF, a small layer of titanium dioxide is placed for binding the plasmonic material to the fiber. And it acts as an adhesive layer. The finite element method is used to perform numerical analyses. After improving the structural parameters, an enhanced sensitivity of 26 000 nm RIU−1 is achieved. Because of its enhanced sensitivity, this sensor is used in a bio-medical application to detect and prevent diseases in the early stage.

Reacting flow characteristics based on the axis-switching phenomenon in a baffled micro combustor with rotated noncircular holes for micro-thermophotovoltaic system

• The geometric features related to the axis-switching phenomenon are numerically investigated for a multihole baffled micro combustor. • In the combustor of noncircular holes, secondary flows are more developed. • The flow mixing and combustion efficiency are improved by noncircular air holes. • The best thermal field for a combustion-based TPV system is obtained for baffles with 30°-rotated square holes and 15°-rotated triangular holes. • The emitter efficiency for TPV applications is better than the swirling flow combustor. For a thermophotovoltaic (TPV) generator, a combustor design for strengthening the axis-switching phenomenon is explored. Various simulations based on a Reynolds stress model and detailed chemical mechanism of GRI 3.0 are performed for methane (CH 4 )–air flames in a multihole baffled combustor. The reacting flow fields are investigated with the baffle plates of rotated square and triangular holes. The spreading and merging of multiple air jets past the baffle plate are significantly affected by rotating noncircular air holes. Considering the crossover location changes of the jet half-width, the air jets have a flow structure that quickly generates the axis-switching phenomenon. Compared with the baffled combustor of circular air holes, the center recirculation zone in the combustor of noncircular holes is enlarged by approximately 200% with a hole rotation. As the hole rotation increases, secondary flows become more complicated and the merging of air jets is quickly finished. Based on these flow structures, the region with the stoichiometric condition is observed in various forms of hexagonal, star, circular, and flower shapes. As a result, the flammable region and combustion efficiency are considerably increased. The flame lengths are roughly evaluated as three times the mixing lengths. From the viewpoint of a heat emitter for the TPV application, the heat transfer on the combustion chamber wall is discussed. Compared with the combustor with circular air holes, the combustor with noncircular air holes shows a 5% increase in flammable region and a 5.9% improvement in combustion efficiency. For a combustion-based TPV system, the best uniformity of wall temperature is observed for baffles with 30°-rotated square holes and 15°-rotated triangular holes and the highest mean wall temperatures are obtained when the flame length is approximately 1/3 of the combustor length.

A novel nested three-ring-core photonic crystal fiber for OAM transmission

A novel nested three-ring-core photonic crystal fiber (PCF) is designed and analyzed. OAM modes are transmitted independently in the three guided mode regions and the nested structure increases the number of OAM modes. In the wavelength range of 1.5–2.0 µm, the PCF shows stable transmission of 46 + 62 + 74 OAM modes. The mode purity of all the eigenmodes is greater than 91% and the isolation parameters remain above 55 dB. The larger effective mode field areas result in ultra-low nonlinear coefficients less than 1.04 m2W−1 and the confinement losses of the supported modes are less than 1.18 × 10−8 dB/m. In addition, the structure comprising circular air holes and silica enables easier manufacturing and the excellent performance also suggest large potential in large-capacity transmission systems.

Modeling of unidirectional radiation of microdisk resonators with small piercing holes by Galerkin method with accurately computed matrix elements

Using the integral-equation-based in-house guaranteed-convergence numerical code, we study the effect of a circular air hole on the frequency, threshold gain and directionality of emission of the whispering-gallery modes of a two-dimensional model of circular-disk microcavity laser. It is shown that a small hole can enhance the directionality greatly and leave the threshold gain intact, if the disk‘s refractive index is large enough and the hole‘s location is chosen properly. This location should be close to the area, in which the same uniform disk, if illuminated with a plane wave, would display a broadband focusing in the form of a hot spot called a photonic jet.