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Ultra-High Refractive Index Sensing Structure Based on a Metal-Insulator-Metal Waveguide-Coupled T-Shape Cavity with Metal Nanorod Defects
摘要： An ultra-high plasmonic refractive index sensing structure composed of a metal–insulator–metal (MIM) waveguide coupled to a T-shape cavity and several metal nanorod defects is proposed and investigated by using finite element method. The designed plasmonic MIM waveguide can constitute a cavity resonance zone and the metal nanorod defects can effectively trap the light in the T-shape cavity. The results reveal that both the size of defects in wider rectangular cavity and the length of narrower rectangular cavity are primary factors increasing the sensitivity performance. The sensitivity can achieve as high as 8280 nm/RIU (RIU denotes the refractive index unit), which is the highest sensitivity reported in plasmonic MIM waveguide-based sensors to our knowledge. In addition, the proposed structure can also serve as a temperature sensor with temperature sensitivity as high as 3.30 nm/°C. The designed structure with simplicity and ease of fabrication can be applied in sensitivity nanometer scale refractive index sensor and may potentially be used in optical on-chip nanosensor.
关键词： T-shape cavity,nanorod defects,temperature sensor,finite element method,refractive index sensor,metal–insulator–metal,plasmonics,sensitivity
更新于2025-09-19 17:13:59
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A Refractive Index Sensor Based on H-Shaped Photonic Crystal Fibers Coated with Ag-Graphene Layers
摘要： An Ag‐graphene layers‐coated H‐shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor with a U‐shaped grooves open structure for refractive index (RI) sensing is proposed and numerically simulated by the finite element method (FEM). The designed sensor could solve the problems of air‐holes material coating and analyte filling in PCF. Two big air‐holes in the x‐axis produce a birefringence phenomenon leading to the confinement loss and sensitivity of x‐polarized light being much stronger than y‐polarized. Graphene is deposited on the layer of silver in the grooves; its high surface to volume ratio and rich π conjugation make it a suitable dielectric layer for sensing. The effect of structure parameters such as air‐holes size, U‐shaped grooves depth, thickness of the silver layer and number of graphene layers on the sensing performance of the proposed sensor are numerical simulated. A large analyte RI range from 1.33 to 1.41 is calculated and the highest wavelength sensitivity is 12,600 nm/RIU. In the linear RI sensing region of 1.33 to 1.36; the average wavelength sensitivity we obtained can reach 2770 nm/RIU with a resolution of 3.61 × 10?5 RIU. This work provides a reference for developing a high‐sensitivity; multi‐parameter measurement sensor potentially useful for water pollution monitoring and biosensing in the future
关键词： H‐shaped optical fiber,graphene,liquid refractive index,photonic crystal fibers,surface plasmon resonance
更新于2025-09-19 17:13:59
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Linear and nonlinear optical properties change in Ag/GeS heterostructure thin films by thermal annealing and laser irradiation
摘要： The photo and thermal annealing induced linear and nonlinear optical properties, structural properties and surface morphology of thermally evaporated Ag/GeS bilayer thin films are reported in the present study. The related changes due to Ag diffusion into GeS layer by annealing at 200 °C and 532 nm laser irradiation have been probed. The X-ray diffraction revealed no structural change whereas the surface structure was viewed by field emission scanning electron microscopy. The optical data recorded by UV–visible spectrophotometer in the range of 500–1200 nm shows the decrease in refractive index (n) and extinction coefficient (k). The Ag diffusion into GeS layer increased the optical band gap due to the decrease of width of the localised states. The single oscillator Wemple–Di Domenico model was used to study the dispersion relation. The third order nonlinear susceptibility (χ(3)) and nonlinear refractive index (n2) were calculated by using suitable semi-empirical relation. The change in density of defects and localised states explained the observed linear and nonlinear changes with annealing and laser irradiation. The homopolar bond to heteropolar bond transformation is noticed from X-ray photoelectron spectroscopy. The observed optical changes can be used in various optical applications.
关键词： Annealing,Laser irradiation,Optical properties,Refractive index,Thin films,Nonlinear properties
更新于2025-09-19 17:13:59
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An Ag-assisted silicon slot waveguide sensor model for mid-infrared spectra gas detection with micro-ring air pressure compensation
摘要： In this paper, we introduced a metal assisted silicon slot waveguide for highly sensitive gas detection. Considering the shortage of refractive index sensing and the influence of air pressure, we choose infrared absorption as the concentration sensing mechanism instead of traditional refractive index sensing on silicon device. Because of the thin metal layer under slot waveguide, the sensitivity of sensor is significantly enhanced. Meanwhile, an air pressure detection based on refractive index sensing is realized for signal compensation, which improves the accuracy of sensor when compared with single mechanism sensor. The simulation results of designed waveguide and sensing application have shown the feasibility and improvement of this new gas sensor.
关键词： on-chip sensor,slot waveguides,refractive index sensing,infrared gas absorption
更新于2025-09-19 17:13:59
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Photoluminescence characterizations and nonlinear optical of PM-355 nuclear track detector film by alpha-particles and laser irradiation
摘要： The imaging processing technique was used for studying a laser beam nature that transmitted through films of PM-355. The thermal nonlinearity of PM-355 films was studied using a 635 nm cw diode laser at 15 mW as the source of excitation. Third order nonlinear optical properties of PM-355 films irradiated with α-particles at different times and pristine sample has been studied using Z-scan technique. The samples showed a negative and large nonlinear refractive index and reverse saturable absorption (RSA) with high values of the nonlinear absorption coefficient. The fluorescence spectra of PM-355 films were investigated at room temperature and wavelength range of 250-500 nm for a pristine film and in different times of exposure to α-particles. The broad peaks were between 350, 420 and 465 nm. All-optical switching property of PM-355 samples irradiated with α-particles at 20 minutes was also studied using the standard pump-probe technique.
关键词： Diffusion,Polymer,Nonlinear refractive index,Saturable Absorption,Fluorescence
更新于2025-09-19 17:13:59
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31.4: <i>Invited Paper:</i> Recent Development of Soluble Hole Injection Material for Printed OLED and QLED Display
摘要： We are developing the soluble hole injection materials and the inks, named ELsource? that can be used as hole injection layer in OLED display. OLED display is one of optical device. Therefore, we developed the hole injection materials with optical properties necessary for that optical devices. We also developed the hole injection material with the deeper ionization potential applicable to QLED display.
关键词： Hole injection layer,Ionization potential,HIL,Refractive index,HIM,Printed,OLED,Optical property,Hole injection material,QLED,Soluble
更新于2025-09-19 17:13:59
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Toroidal metasurfaces integrated with microfluidic for terahertz refractive index sensing
摘要： A terahertz refractive index sensor consisting of toroidal dipole resonance metasurface integrated with microfluidic channel is proposed. The excitation of toroidal dipole resonance in this metasurface and the localized electromagnetic field enhancement in microfluidic channel are investigated comprehensively. Numerical results show that the calculated quality factor and the corresponding figure of merit can reach 1103 and 244, much higher than previously reported terahertz metamaterials sensors. Moreover, the refractive index sensing capabilities of non-polar and polar liquids are also investigated, which demonstrate the resonant frequency shift does not depend on the losses of analytes and show this device can be used for sensing various materials, including highly absorptive materials. This proposed structure can be extended to work in other frequency regions and has potential applications in high performance gases, liquids and biological materials sensing.
关键词： toroidal dipole,metasurfaces,microfluidic,refractive index sensing,terahertz
更新于2025-09-19 17:13:59
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Broadband Anti-Reflection in Black Silicon Fabricated by Two-Step Silver-Assisted Wet Chemical Etching for Photovoltaics
摘要： This paper reports broadband anti-reflection in black silicon (b-Si) fabricated by two-step metal-assisted chemical etching (MACE) for potential photovoltaic (PV) applications. The method involves deposition of silver nanoparticles (Ag NPs) in aqueous solution of HF:AgNO3, followed by etching in HF:H2O2:DI H2O solution for different duration (10-25 s). Effects of etching time towards surface morphological and optical properties of b-Si nanowires are investigated. Surface morphological characterization confirms presence of b-Si nanowires with heights of 350-570 nm and diameter of 150-300 nm. The b-Si nanowires exhibit outstanding broadband anti-reflection due to refractive index grading effect. This is represented as weighted average reflection (WAR) in the 300-1100 nm wavelength region. After 20 s of etching, b-Si nanowires with height of 570 nm and width of about 200 nm are produced. The nanowires demonstrate WAR of 5.5%, which represents the lowest WAR in this investigation. This results in absorption of 95.6% at wavelength of 600 nm. The enhanced broadband light absorption yields maximum potential short-circuit current density (Jsc(max)) of up to 39.7 mA/cm2, or 51% enhancement compared to c-Si reference. This facile b-Si fabrication method for broadband enhanced anti-reflection could be a promising technique to produce potential PV devices with high photocurrent.
关键词： black silicon,nanowires,silver-assisted etching,refractive index grading,anti-reflection
更新于2025-09-19 17:13:59
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Laser-induced incandescence on metal nanoparticles: validity of the Rayleigh approximation
摘要： Time-resolved laser-induced incandescence (TiRe-LII) is increasingly being used to characterize non-carbonaceous nanoparticles. However, there exist several measured phenomena, particularly on metal nanoparticles, that cannot be explained using traditional models. This paper shows that some of these phenomena may be due to errors caused by the Rayleigh approximation of Mie theory, which is a standard approach for modeling the spectral absorption of carbonaceous nanoparticles but is generally invalid for metal nanoparticles. Other measurement phenomena can be explained by combining Mie theory with a polydisperse particle size distribution or by considering the change in the refractive index as the nanoparticles melt. Also, the effect of the nanoparticle charge on optical properties is investigated and is found to have a negligible effect on the TiRe-LII model.
关键词： Mie theory,Polydisperse particle size distribution,Metal nanoparticles,Refractive index,Nanoparticle charge,Rayleigh approximation,Laser-induced incandescence
更新于2025-09-19 17:13:59
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Analysis and Simulation of a Novel Localized Surface Plasmonic Highly Sensitive Refractive Index Sensor
摘要： Dividing a metal nanoparticle into smaller components and the occurrence of the plasmonic phenomenon in the gap between these components can improve the sensitivity of the detector to variation of the refraction coefficient of liquid. In this paper, in a constant volume of metal, a golden disk is divided into two rings and one smaller disk. With a proper arrangement of these components, the surface plasmon resonance phenomenon takes place at the wavelength of 945.7 nm. The occurrence of this phenomenon increases the field in the distance between nanoparticles surrounded by liquid. The sensitivity of the detector that designed using nanodisks is 300 nm/RIU while it increases to 500 nm/RIU for the new structure. The increase of LSPR displacement, for a variation of 0.01 in the liquid refraction coefficient, from 3 nm for a disk to 5 nm for a proposed structure verifies a 67% improvement in the sensitivity of the sensor.
关键词： Refractive index sensor,Nanodisks,Plasmon,Plasmonic effects
更新于2025-09-19 17:13:59