Wide Range Of Refractive Indices Research Articles

Theoretical study of perovskite nano material based surface plasmon resonance biosensor for cancers cell detection

The present study reports screening of cancer cells at the earliest stages using prism coupling-based surface plasmon resonance biosensors in a theoretical manner. The SPR sensors designed on Kretschmann configuration consisting of several layers like silver (Ag) metal, beryllium oxide (BeO) and hetero-structure BlueP/WSe2 layer deposited over BK7 glass prism. For maximum light absorption, a perovskite nano material, barium titanate (BaTiO3) layer is placed between BeO and hetero-structure BlueP/WSe2 to enhance the angular sensitivity. The light of 633 nm wavelength has been used for excitation of surface plasmon at metal dielectric interface. The refractive index of cancer cells lies between 1.360 and 1. 400. The optimized angular sensitivity of 216°/RIU and 360°/RIU for PCI-2 (normal, adrenal gland cancer), 248°/RIU and 254°/RIU for MDA-MB-231(normal, breast cancer cell) as well as 248°/RIU and 254°/RIU for MCF-7 (normal, breast cancer cell) respectively has been obtained. The maximum optimized angular sensitivity for adrenal gland cancer is 360°/RIU on employing perovskite layer. The sensor offers excellent performance parameters and covers wide range of refractive index sensing.

Designing multifunctional silica coatings for enhanced broadband antireflection and microfiber contamination sensing

Multifunctional silica coatings find diverse applications in solar energy conversion and pollution monitoring sensors due to their suitability for mass manufacturing. However, the challenge lies in producing robust silica coatings on a large scale with tunable refractive index. This work presents a two-step acid/base catalyzed sol–gel process for synthesizing multifunctional silica coatings with adjustable refractive index. The coatings' porous microstructure allows them to be used as double-layer broadband antireflective coatings and enhances the sensitivity of contamination sensors. The optimized double-layer coatings, designed using computer-aided techniques, demonstrate excellent broadband antireflective performance in the visible regions and high environmental durability. They achieve a maximum transmittance of 99.87% at 591 nm, with an average transmittance of 99.40% in the visible region (400–800 nm) and 98.63% from 400 nm to 1100 nm. Additionally, the coatings exhibit robust abrasion resistance and enhanced surface hydrophobicity with a water contact angle increased from 30° to 126° through HMDS treatment. This work investigated the particle growth mechanism and the relationship between silica nanoparticle microstructure and antireflective coating properties. Furthermore, the coatings' presence of abundant micropores allows successful application onto microfiber contamination sensors, the additional loss increases from 26.40 dB to 37.69 dB over 140 min and decreases to 31.55 dB within one minute, demonstrating rapid adsorption and desorption rates. The work successfully achieves a wide range of adjustable refractive index while maintaining excellent mechanical and optical properties, addressing the traditional trade-off between high porosity and poor mechanical stability. These rationally designed multifunctional silica coatings hold great potential for high-quality broadband antireflection and high sensitivity in microfiber contamination sensing.

Metamaterial as perfect absorber for high sensitivity refractive index based biosensing applications at infrared frequencies

In this paper, we introduce a novel design of a metamaterial unit cell absorber, which is based on a metal/insulator/metal sandwich structure. The design is subjected to comprehensive finite element method computational analysis to ensure accurate and reliable results. The proposed metamaterial sandwich structure demonstrates exceptional absorption performance, achieving a nearly perfect absorption rate of 99.996% at the resonance infrared frequency of 39.8 THz. To provide a detailed theoretical explanation of nearly perfect absorption, we employ the effective medium theory, impedance matching, and field distribution analysis. Additionally, we have optimized the structural parameters of the sensor to maximize its absorption peak. This includes optimizing the thickness of the gold (Au) layer (from 0.03 to 0.28 μm), the distance between the L shape corners (from 0.60 to 0.90 μm), and the thickness of SiC dielectric spacer (from 0.20 to 0.45 μm). Furthermore, we showcase the remarkable sensitivity of the proposed metamaterial unit cell in detecting subtle changes in the refractive index through the implementation of a sensing medium setup in our model. Remarkably, we achieve a frequency shift sensitivity of 3.74 THz/RIU, along with a quality factor of 10.33, for a wide range of refractive indices (1.0–2.0). Moreover, for cancer detection, we attain a sensitivity of 3.5 THz/RIU. These findings highlight the exceptional performance of our approach in accurately detecting changes in refractive index, making it a promising candidate for various sensing applications. The novelty of our work lies in the design of a metamaterial unit cell structure. This configuration exhibits several noteworthy features, including wide incident angle () coverage up to 60°, polarization insensitivity, exceptional frequency shift sensitivity, high absorption peaks across a wide range of refractive indices, and the ability to distinguish cancer cells from healthy ones.

Dual core photonic crystal fiber based plasmonic refractive index sensor with ultra-wide detection range.

In this study, an ultra-wide range plasmonic refractive index sensor based on dual core photonic crystal fiber is suggested and analyzed numerically. The proposed design achieves fabrication feasibility by employing external sensing mechanism in which silver is deposited onto the flat outer surface of the fiber as plasmonic material. A thin layer of titanium oxide (TiO2) is considered on top of the silver layer for preventing its oxidation problem. The sensor attains identification of a vast array of analytes consisting a wide range of refractive indices of 1.10 - 1.45. It achieves a maximum spectral sensitivity of 24300 nm/RIU along with its corresponding resolution of 4.12 × 10-6 RIU. The maximum figure of merit of the sensor is 120 RIU-1. The sensor also supports amplitude interrogation approach and exhibits a maximum amplitude sensitivity of 172 RIU-1. The impact of the design parameters such as radius of air holes, polishing distance, thickness of silver and titanium oxide layers are investigated thoroughly. An ultra-wide detection range with high sensitivity, fabrication feasibility, and easy application make the sensor a potential candidate for detection of a wide array of bio-originated materials, chemicals, and other analytes.

High-accuracy wide-range refractive index demodulation based on under-sampled fiber F-P cavity length spectrum.

A scheme of fiber Fabry-Perot (F-P) cavity refractive index (RI) demodulation named under-sampled length spectrum retrieval (ULSR) is proposed. Unlike the wavelength spectrum method, ULSR can be used for physical quantity detection with just a monochromatic laser and photodetectors, avoiding the need for wideband lasers or expensive infrared spectrometers. Eight F-P cavities of different lengths were fabricated to sample the cavity length spectrum, and then the obtained under-sampled length spectrum was used to demodulate the RI of F-P cavity fillings. It was demonstrated that the ULSR system can achieve an index measurement accuracy of 1 × 10-4 in the glucose solution index range of 1.3294-1.3746 at wavelength λ = 1.55 µm. An index demodulation with higher accuracy and wider range is expected when more than 8 F-P cavities are used. The proposed scheme, with advantages of low system complexity, low cost, high reliability, high detecting accuracy, and wide detecting range, holds great promise for facilitating the wide application of F-P cavity sensors. Additionally, ULSR liberates wavelength freedom, making it a strong candidate for multiplexed sensing based on wavelength division multiplexing.

High Sensitivity and Wide Range Refractive Index Sensor Based on Surface Plasmon Resonance Photonic Crystal Fiber.

In order to detect the refractive index (RI) of high refractive index materials such as trichlorobenzene and aniline in the near-infrared and mid-infrared spectra and expand the detection range of the refractive index, a surface plasmon resonance (SPR) photonic crystal fiber (PCF) sensor based on an elliptical sensing channel is proposed for high refractive index detection. The fiber core and the analyte channel are surrounded by two types of air holes with different sizes. When the surface plasmon resonance effect appears at the interface between the fiber core and the elliptical sensing layer, obvious resonance peaks appear in the near-infrared and mid-infrared bands. The full vector finite element method (FEM) is used to study the sensing characteristics of the sensor and the influence of structural parameters on the resonance peak. The results demonstrate that the sensor achieves detection in the refractive index range of 1.41-1.58, in the wavelength range of 1600-3200 nm. The average wavelength sensitivity is 9217.22 nm/RIU, and the refractive index resolution is 10.85 × 10-6 RIU. The proposed sensor realizes high refractive index detection in the near-infrared and mid-infrared bands, and obtains an ultra-wide detection range and higher sensitivity. The sensor has broad application prospects in chemical detection, biomedical sensing and other fields, and provides a theoretical reference for the design of a photonic crystal fiber surface plasmon resonance sensor.

Mesoporous Metal Fluoride Nanocomposite Films with Tunable Optical Properties Derived from Precursor Instability.

The precisely tailored refractive index of optical materials is the key to utilizing and manipulating light during its propagation through the matrix, thereby improving their application performances. In this paper, mesoporous metal fluoride films with engineered composition (MgF2 :LaF3 ) are demonstrated to achieve finely tunable refractive indices. These films are prepared using a precursor-derived one-step assembly approach via the simple mixing of precursor solutions (Mg(CF3 OO)2 and La(CF3 OO)3 ); then pores are formed simultaneously during solidification owing to the inherent instability of La(CF3 OO)3 . The mesoporous structures are realized through Mg(CF3 OO)2 and La(CF3 OO)3 ions, which interacted with each other based on their electrostatic forces, providing a wide range of refractive indices (from 1.37 to 1.16 at 633 nm). Furthermore, it is systematically several MgF2(1-x) -LaF3(x) layers with different compositions (x=0.0, 0.3, and 0.5) to form the graded refractive index coating that is optically consecutive between the substrate and the air for broadband and omnidirectional antireflection. An average transmittance of ≈98.03% (400-1100nm) is achieved with a peak transmittance of ≈99.04% (at 571nm), and the average antireflectivity is maintained at ≈15.75% even at an incidence of light of 65° (400-850nm).

Ag/CdS surface plasmon simulation systems for gas sensor

In this work, the Surface Plasmon Resonance (SPR) sensor simulated for a wide range of wavelengths and refractive index. The Kretschmann configuration of the suggested sensor is Silver (Ag) with a thickness of 45 ​nm, and Cadmium Sulfide (CdS) dielectric with variable thickness (10 ​nm–80 nm) that deposited on FD60 Dense flint prism. The sensing medium is gas which includes air and different refractive indexes (Δn ​= ​0, 0.02, 0.05, and 0.1) to consider most gas cases. The wavelength light range studied from 100 nm to 1000 ​nm. The results show that SPR appeared strongly in the Infrared range between 900 ​nm and 1000 ​nm. It is weakly appeared in the visible range and cannot be noticed in the ultraviolet region. The sharpest and longest SPR dip occurred in the Infrared range. The smallest value of full-width half maxima (FWHM) was 0.4° at CdS thickness of 10 ​nm, and the longest SPR dip has 0.97° at CdS thickness of 60 ​nm. The smallest and longest value of FWHM dip occurred at wavelength 1000 ​nm and n ​= ​0.02. Hence, the better detection accuracy and sensitivity of the SPR sensor were in the infrared region at wavelength 1000 ​nm and n ​= ​0.02 for the suggested sample. So, the range of working wavelengths depending on the sample design.

Tunable and ultrasensitive sensor covering terahertz to telecommunication range based on a Fabry–Perot interference of graphene plasmonic waves

We present an ultrasensitive tunable terahertz (THz) sensor that comprises monolayer graphene-based gratings integrated with a Fabry-Perot (FP) cavity through precisely numerical modeling. Due to the vertical polarization of the incident light on the graphene gratings, they act as an electric dipole, which causes interference in the propagation of plasmonic waves, and provides an excellent foundation for a wide range of ultrasensitive refractive index (RI) sensing with an ultra-high-quality factor (Q). The main advantage of the proposed structure is not only sensing a wide range of refractive indices but due to its unique physical mechanism, it covers electromagnetic waves from a few terahertz to 300 THz, including the telecommunication bands. The primary physical mechanism in the proposed sensor is the FP interference in its active area. Also, due to the extreme sensitivity of FP interference (FPi) to the (RI) of the medium and the active area, the proposed structure owns an ultra-high sensitivity and Q. Our full-wave electromagnetic simulations demonstrate a frequency sensitivity of up to 83 THz per RI unit (RIU) and a high value of Q near 275. In addition, the proposed structure for index sensing has the functionality to be tuned in any desired frequency of interest from THz to the Mid-IR range and telecommunication band, which entirely covers 1–300 THz. The chemical potential of graphene can be electrically controlled to tailor the sensing capability and incident frequency. According to the applied gate voltage, the proposed structure can detect ammonia concentration in water with a high sensitivity of 70–85 THz/RIU and a quality factor of more than 275. The error of the ammonia concentration sensing is smaller than 0.5%. In addition, the proposed structure can detect different types of matter, including various microfluidics, air, gasoline, liquid paraffin, ethanol, glycerin, and glucose. The graphene plasmonic grating method suggested here is a good contender for on-chip integrated THz to mid-IR, including telecommunication bio-sensors.

Design and numerical analysis of a circular SPR based PCF biosensor for aqueous environments

This paper presents the design and numerical analysis of a circular photonic crystal fiber (PCF) biosensor based on surface plasmon resonance (SPR) for aqueous environments. The proposed biosensor has a geometrical design that uses the cladding at the fiber's exterior to simplify the gold and analyte deposition process. The sensing characteristics and performances of the proposed biosensor are fully investigated with the finite element method. The investigation indicates that the plasmonic material's thickness affects the biosensor's performance. The results of the proposed biosensor demonstrate a wide refractive index range of 1.30 to 1.44, with the highest wavelength or spectral sensitivity as 21,000 nm/RIU and the highest resolution as 9.09×10−6 RIU. The proposed biosensor has a straightforward geometric profile. The proposed biosensor is stable and suited for aqueous surroundings and wide-range detection applications.

Ultrasensitive Refractive Index Sensing Based on Hybrid High-Q Metasurfaces

High sensitivity and a large quality factor (Q) are two desirable goals to achieve a high figure of merit (FoM) in refractive index (RI) sensing. However, simultaneously satisfying these two goals is challenging. Herein, we propose a new class of hybrid high-Q metasurfaces, which are dielectric arrays standing on a Au plasmonic nanofilm, possessing the advantages of both high RI sensitivity and a large Q. The hybrid metasurface can support the plasmon-coupled lattice mode, which has extremely narrow full width at half-maximum (fwhm) resulting in a high-Q. The hybrid metasurface can be fabricated by a facile straightforward lithography technique and exhibits ultrahigh FoM values over a wide RI range (1–1.384) due to its narrow fwhm (smaller than 1 nm) and tunable high RI sensitivity. The highest Q and FoM values of 2370 and 1431 were experimentally demonstrated, respectively, giving the proposed hybrid metasurface great potential for building advanced optical biosensors in future applications.

The discovery of the effect of compositional disorder on the opto-electronic properties of the deformed InGaAsP quaternary

This article presents a theoretical study of the optoelectronic properties of InGaAsP alloys fabricated on three different substrates: InP, GaA, and ZnSe. Particular attention has been paid to the study of bandgap energy along points of high symmetry in the Brillouin zone, absorption coefficient, and refractive index of materials without compositional disorder and subjected to deformation. Our goal is to expand the range of optoelectronic properties. We found that the absorption coefficient of the deformed InGaAsP/InP material in the absence of disorder varies between 9.66×104cm−1 and 1.35×105cm−1 changing the content of phosphorus and gallium, making it possible to provide a wide range of refractive indices [3.06, 3.84] compared to GaAs substrates [2.67, 3.02] and ZnSe [2.69, 3.05]. This refractive index contrast can be exploited in the design of optical waveguides.

Antimonene-Coated Uniform-Waist Tapered Fiber Optic Surface Plasmon Resonance Biosensor for the Detection of Cancerous Cells: Design and Optimization.

For early-stage cancer detection, a novel design of graphene-antimonene-coated uniform-waist tapered fiber optic surface plasmon resonance (SPR) biosensor is demonstrated. The proposed optical biosensor outperforms over a wide range of refractive index (RI) variations including biological solutions and is designed to detect various cancerous cells in the human body whose RIs are in the range of 1.36-1.4. Here, antimonene is used to enhance the performance of the designed SPR sensor for sensing cancer analytes because of its high binding energy toward adsorption of biomolecules and large active surface area. The design and analysis of the sensor are done with the help of a transfer matrix method-based simulation platform, and the effect of the taper ratio is also studied. The performance of the proposed SPR biosensor is evaluated with performance parameters such as sensitivity, full width at half maximum, detection accuracy (DA), figure of merit (FOM), and limit of detection (LOD). The numerical results show that the designed sensor is able to provide a sensitivity of 7.3465, 10.9250, 11.8914, and 15.2414 μm/RIU, respectively, for sensing skin, cervical, blood, and adrenal gland cancer with a maximum FOM of 131.1525 RIU-1, DA of 14.2126 μm-1, and LOD of 7.2 × 10-5 RIU. Based on the derived results, the authors believe that the designed SPR sensor could practically find its potential applications in the field of medical science for the early-stage diagnosis of cancer and hence, opens a new window in the field of biosensing.

Highly sensitive surface plasmon resonance sensor for refractive index detection of Helicobacter Pylori

Helicobacter Pylori (H-Pylori) is gram-negative and spiral micro-organism that is responsible for its colonization in gastric microniche. The outcome of recent studies indicates that the development of H-Pylori in human bodies results in peptic ulcers, gastric mucosa, and gastric cancer. Therefore, on-time diagnosis of H-Pylori infection is very important to overcome its adverse effects. In this work, we have adopted the surface plasmon resonance (SPR) sensor for the detection of H-Pylori infection in human bodies. The SPR phenomenon is initiated by placing a 40–50 nm thick layer of gold nanoparticles on the flat surface of the glass prism. Four different configurations are designed by immobilizing a layer of biocompatible materials. Probe 1, 2, 3, and 4 are designed by immobilizing the layers of silicon oxynitride (SiON), molybdenum oxide (MoS2), graphene oxide (GO), and graphene, respectively. Added to this, the specificity of all the sensor structures is attained by functionalizing them with a 0.11 nm thick layer of urease enzyme, which oxidizes only in the presence of H-Pylori. Thereafter, the sensing analysis of all the sensor probes is done in a wide range of refractive index (RI) from 1.3227 to 1.3382 which corresponds to the RI of human urine in presence of H-Pylori. The performance analysis of the sensor is done in the terms of sensitivity, detection accuracy (DA), quality factor (QF), the figure of merit (FoM), and dip of a figure of Merit (DFoM). Added to this, the signal propagation through all the sensor structure is analyzed by using two-dimensional finite-difference-time-domain (FDTD) method-based tool.

Wedged Fiber Optic Surface Plasmon Resonance Sensor for High-Sensitivity Refractive Index and Temperature Measurements.

Here, we experimentally demonstrate a wedged fiber optic surface plasmon resonance (SPR) sensor enabling high-sensitivity temperature detection. The sensing probe has a geometry with two asymmetrical bevels, with one inclined surface coated with an optically thin film supporting propagating plasmons and the other coated with a reflecting metal film. The angle of incident light can be readily tuned through modifying the beveled angles of the fiber tip, which has a remarkable impact on the refractive index sensitivity of SPR sensors. As a result, we measure a high refractive index sensitivity as large as 8161 nm/RIU in a wide refractive index range of 1.333-1.404 for the optimized sensor. Furthermore, we carry out a temperature-sensitivity measurement by packaging the SPR probe into a capillary filled with n-butanol. This showed a temperature sensitivity reaching up to -3.35 nm/°C in a wide temperature range of 20 °C-100 °C. These experimental results are well in agreement with those obtained from simulations, thus suggesting that our work may be of significance in designing reflective fiber optic SPR sensing probes with modified geometries.

Phase change material and MXene composited refractive index sensor for a wide range of sensing applications at visible and infrared wavelength spectrum

We present the numerical investigation of the phase change material and MXene-based wide range refractive index sensor for the visible and infrared spectrum. The proposed structure is investigated in three layered structures, consisting of layers of Ge2Sb2Te5, Ti3C2TX, silica, and silver materials. We have presented the reflectance response of these multi-layered structures for refractive index ranges 1–2.2. The overall design is simulated using the finite element method of computational technique. We have also investigated the effect of different material heights on the overall performance of the structure. We have presented several resonating trace equations to identify the sensing behaviour for a specific wavelength range and refractive index values. The proposed design is also investigated for the different oblique angles of the incident condition to identify the wide-angle stability of the proposed structure. Numerical investigation of the proposed structure can help to design biosensors to detect a wide range of biomolecules such as cancerous, haemoglobin, urine, saliva-cortisol and glucose.

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.

Particle-in-cell simulations on parametric instability of the lower hybrid wave

Lower hybrid (LH) wave is an effective tool for current drive (CD) on tokamak devices. Parametric instability (PI) has always been a troubling phenomenon decreasing the lower hybrid current drive efficiency. In this work, the PI behavior of the LH waves for plasma parameters on the Experimental Advanced Superconducting Tokamak is investigated via first-principle simulation with a two-dimensional full-particle-in-cell method. The PI processes where an LH pump wave decays into another LH sideband and a low-frequency mode [ion sound quasi-mode (ISQM) or ion cyclotron quasi-mode (ICQM)] are observed in simulations. The ICQM-type and ISQM-type decay channels dominate, respectively, in the high- and low-plasma regimes while appearing simultaneously in the intermediate regime, which agrees well with the theoretical prediction by solving the parametric dispersion relation. In addition, for both the decay channels, their LH sidebands are excited with a wide range of parallel refractive index N∥ up to 30.0, which can resonantly interact with thermal electrons. The resulting electron heating can be enhanced due to overlap of resonances between the electrons and sidebands. Such electron heating not only dissipates the wave energy in the edge plasma but produces a significant portion of fast electrons, which may seriously affect tokamak discharges. The ion cyclotron heating due to the ICQMs is also observed in simulations.

Infrared D-type photonic crystal fiber sensor for special drug detection and wide-range refractive index detection

In the field of drug inspection, the refractive indices (RIs) of many halogenated ethers and drugs are in the lower range; for example, the RI of anesthetic sevoflurane is approximately 1.27. Infrared spectral detection technology has significant advantages in the field of drug detection; to realize the RI sensing of such drugs in the infrared region, a D-shaped photonic crystal fiber sensor based surface plasmon resonance was investigated in this study. The side polishing adopted here can significantly shorten the distance between the core and metal layer, making the energy of the core easier to detect, reducing the difficulty of coating the metal layer, and improving the performance of the sensor. The structure is provided with two large-sized air holes on both sides of the fiber core, so that the sensor is suitable for sensing in the low RI range and has high wavelength sensitivity in the low RI range. The sensor works mainly in the infrared band, with a detection range of 1.20–1.34, maximum wavelength sensitivity of 24,000 nm/RIU, and resolution of 4.1667 × 10 − 6 R I U . The sensor has excellent performance and is easy to manufacture due to the simple structure; it has broad application prospects in low RI range detection fields such as biomedicine, drug detection, environmental monitoring, and water quality monitoring.

High-Performance of Star-Photonics Crystal Fiber Based on Surface Plasmon Resonance Sensor

Photonic Crystalline (PCF)-based SPR (Surface Plasmon Resonance) sensors continue to develop and achieve goodperformance, but in previous studies, PCF-SPR only has a small refractive index range detection, complex geometricstructure, and low sensitivity. In this paper, we investigate the performance of the Star-shaped PCF-SPR sensor(S-PCF-SPR) in detecting the refractive index of the analyte. We performed numerical simulations using the finite elementmethod (FEM) based on COMSOL Multiphysics version 5.6. It was found that S-PCF-SPR can detect analytes in a widerefractive index range from 1.3 to 139 RIU. S-PCF-SPR has a maximum wavelength sensitivity of 12000 nm/RIU, and thesensor resolution resulting from S-PCF-SPR 5.4 × 10-5. These results indicate that the S-PCF-SPR can be used as a sensorfor sensitive analyte sensing applications and has good sensor resolution.