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The third-order nonlinear optical properties of gold nanoparticles-methylene blue conjugation
摘要： Third-order nonlinear properties of a thiazine dye (methylene blue (MB)) and a plasmonic nanoparticle (gold nanoparticles (GNPs)) have been studied by Z-scan method with a 50 mW continues wave (CW) diode pumped solid state laser (DPSSL) operating at 532 nm. The nonlinear parameters (nonlinear refractive (NLR) index (n2) and nonlinear absorption (NLA) coefficient (β)) are determined. The mechanism of the observed NLA and nonlinear refraction is attributed respectively to reverse saturable absorption (RSA) and thermal nonlinear effects. The magnitude of the measured NLR index (n2) and NLA coefficient (β) are founded to be the order of 10?8 cm2/W and 10?4 cm/W respectively. The effect of MB and GNPs on each other has been studied. Z-scan experiments for GNPs-MB conjugation shows noticeable increase in nonlinear parameters.
关键词： Z-scan method,Metal nanoparticles,Nonlinear optics,Organic dye,Nonlinear refractive index,Nonlinear absorption coefficient
更新于2025-09-09 09:28:46
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KRIGING-PARETO FRONT APPROACH FOR THE MULTI-OBJECTIVE EXPLORATION OF METAMATERIAL TOPOLOGIES
摘要： Metamaterials provide the opportunity for designers to create customisable artificial materials by independently tailoring the electric and magnetic response of sub-wavelength geometric structures to electromagnetic energy. Due to the increased complexity of these geometric structures, exacerbated by the increased interest in generating inhomogeneous and anisotropic metamaterials, direct optimisation of these designs using conventional approaches often becomes impractical and limited. In order to alleviate this issue, we propose an alternative optimisation approach which exploits the Kriging methodology in conjunction with an adaptive sampling plan to simultaneously optimise multiple conflicting objectives. Results show the effectiveness of the outlined algorithm in calculating a uniform spread of optimal trade-off designs, balancing the real and imaginary components of the refractive index over a wide range of values.
关键词： Kriging,Metamaterials,Refractive Index,Multi-Objective Optimisation,Pareto front
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - Lausanne (2018.7.29-2018.8.2)] 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - An Ultra-Sensitive Glucose Sensor by Using Metamaterial-Based Microfluidic Chip
摘要： A large-scale lithography-free metamaterial (MM) is presented, which is integrated with a microfluidic chip for effective glucose sensing. MM is composed of hybrid nanopillars fabricated with SiO2 and Au thin-films on Si substrate. It exhibits angle-independence, and polarization-independence, which are the most important factors for color filters for industrial applications. The resonance shift is 56 nm with a stable bandwidth (~30 nm) by varying concentration of glucose solution. The sensitivity is 158 nm/RIU and the corresponding figure-of-merit is 5.3.
关键词： lithography-free,plasmonics,refractive index sensors,chemical sensors,metamaterials
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - Lausanne (2018.7.29-2018.8.2)] 2018 International Conference on Optical MEMS and Nanophotonics (OMN) - A Large-Scale, Omnidirectional, and Polarization-Independent Metamaterial-Based Chemical Sensor
摘要： We develop an effective method for volatile organic solutions (VOS) sensing by using metamaterial with hybrid nanopillars to form a metamaterial-based chemical sensor (MCS). It exhibits large-scale, omnidirectional, and polarization-independence characterizations, which are the most important factors for sensors applications. The experiment results indicate the sensitivity and figure-of-merit of MCS are 71 nm/RIU and 3.5, respectively. The proposed MCS can successfully recognize inorganic and organic solutions for chemical sensors in the UV-visible wavelength range.
关键词： lithography-free,plasmonics,refractive index sensors,chemical sensors,metamaterials
更新于2025-09-09 09:28:46
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[ASME ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting - Montreal, Quebec, Canada (Sunday 15 July 2018)] Volume 1: Flow Manipulation and Active Control; Bio-Inspired Fluid Mechanics; Boundary Layer and High-Speed Flows; Fluids Engineering Education; Transport Phenomena in Energy Conversion and Mixing; Turbulent Flows; Vortex Dynamics; DNS/LES and Hybrid RANS/LES Methods; Fluid Structure Interaction; Fluid Dynamics of Wind Energy; Bubble, Droplet, and Aerosol Dynamics - Refractive Index Matching for Optical Flow Investigation With High Density Stratification
摘要： Turbulent mixing in density stratified environments represents a challenging task in experimental turbulence research. When optical measurement techniques like Particle Image Velocimetry (PIV) are applied to stratified liquids, it is common practice to combine two aqueous solutions with different densities but equal refractive indices. As a result, light deflections/distortions due to the mixing of the fluids can be suppressed. While refractive image matching (RIM) was developed in the late ‘70s, the limit of a 4% density ratio had yet to be reported before this work. In the present work, a methodology based on the behavior of changes in a multi component methodology allows RIM for solutions with higher density differences. The applicability of this methodology is experimentally demonstrated with a turbulent buoyant jet using a ternary combination of water, isopropanol and glycerol, for which an index matched density ratio of 8.6% has been achieved (Krohn et al. 2018). Measurements were conducted with a high fidelity synchronized PIV/PLIF system and the results are qualitatively compared in terms of turbulent statistics.
关键词： PIV,density stratification,refractive index matching,PLIF,Turbulent mixing
更新于2025-09-09 09:28:46
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First-principles investigation of the electronic band structures and optical properties of quaternary <i>A</i> Ba <i>MQ</i> <sub/>4</sub> ( <i>A</i> = Rb, Cs; <i>M</i> = P, V; and <i>Q</i> = S) metal chalcogenides
摘要： In this paper, we study the optoelectronic properties of quaternary metal chalcogenide semiconductor ABaM Q4 (A = Rb, Cs; M = P, V; and Q = S) compounds using state-of-the-art density functional theory (DFT) with TB-mBJ approximation for the treatment of exchange-correlation energy. In particular, the electronic and optical properties of the relaxed geometries of these compounds are investigated. Our first-principles ab-initio calculations show that the CsBaPS4 and RbBaPS4 compounds have direct bandgaps whereas the CsBaVS4 compound exhibits indirect bandgap nature. Importantly, the theoretically calculated values of the bandgaps of the compounds are consistent with experiment. Furthermore, our analysis of the electronic charge densities of these compounds indicates that the above quaternary chalcogenides have mixed covalent and ionic bonding characters. The effective masses of these compounds are also calculated which provide very useful information about the band structure and transport characteristics of the investigated compounds. Similarly, high absorptivity in the visible and ultraviolet regions of the electromagnetic spectrum possibly predicts and indicates the importance of these materials for potential optoelectronic applications in this range.
关键词： energy band structure,electronic charge densities,optical conductivity,Chalcogenides,refractive index,dielectric constants,optical reflectivity
更新于2025-09-09 09:28:46
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The Use of Index-Matched Beads in Optical Particle Counters
摘要： In this paper, we demonstrate the use of 2-pyridinemethanol (2P) aqueous solutions as a refractive index matching liquid. The high refractive index and low viscosity of 2P-water mixtures enables refractive index matching of beads that cannot be index matched with glycerol-water or sucrose-water solutions, such as silica beads that have the refractive index of bulk fused silica or of polymethylmethacrylate beads. Suspensions of beads in a nearly index-matching liquid are a useful tool to understand the response of particle counting instruments to particles of low optical contrast, such as aggregated protein particles. Data from flow imaging and light obscuration instruments are presented for bead diameters ranging from 6 μm to 69 μm, in a matrix liquid spanning the point of matched refractive index.
关键词： bead,particles,light obscuration,flow imaging,refractive index,flow microscopy
更新于2025-09-09 09:28:46
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Empirical expressions for the spectral dependence of the refractive index for the case of thin-film silicon and some of its common alloys
摘要： We aim to model the spectral dependence of the refractive index associated with thin-film silicon, and some of its common alloys, using a series of elementary polynomial fits. For the purposes of this particular analysis, experimental data sets for the refractive index as a function of the photon energy corresponding to samples of thin-film silicon, and its alloy with germanium and carbon, prepared through evaporation, plasma enhanced chemical vapor deposition, and dc sputtering, are considered, this range of results providing a reasonably representative sampling over the thin-film silicon genome. The results of this analysis, i.e., the polynomials that arise from these fits, are explicitly tabulated. We believe that such models will offer the thin-film silicon community a number of advantages, including the ease with which such a result can be replicated, manipulated, and employed by fellow thin-film silicon researchers in their analyzes of this material system.
关键词： spectral dependence,alloys,refractive index,polynomial fits,thin-film silicon
更新于2025-09-09 09:28:46
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Tunable triple-band graphene refractive index sensor with good angle-polarization tolerance
摘要： In this article, we design a triple-band graphene refractive index sensor with good angle-polarization tolerance, which is composed of graphene elliptic-circular nanodisk resonators periodically arranged on a dielectric substrate. The numerical results indicate that the resonant wavelengths of three modes of graphene resonators show consecutively linear tunability when the refractive index of the surrounding medium varies, and the sensitivity is up to 11.56 μm/RIU. The sensing range can be further adjusted by controlling the doping level of graphene. In addition, the proposed graphene sensor maintains polarization insensitivity over a wide angular range (0-60°), showing very good angle-polarization tolerance. This work enables us to achieve a tunable triple-band sensor and provides potential value for label-free biomedical sensing.
关键词： graphene,surface plasmon resonance,refractive index sensor,metamaterials
更新于2025-09-09 09:28:46
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Composite GaN-C-Ga (‘GaCN’) Layers with Tuneable Refractive Index
摘要： This article describes novel composite thin films consisting of GaN, C and Ga (referred to as ‘GaCN’, as an analogue to BCN and other carbonitrides) as a prospective material for future optical applications. This is due to their tuneable refractive index that depends on the carbon content. The composites are prepared by introducing alternating pulses of trimethylgallium (TMG) and ammonia (NH3) on silicon substrates to mimic an atomic layer deposition process. Since the GaCN material is hardly reported to the best of our knowledge, a comprehensive characterization is performed to investigate into its chemical nature, primarily to determine whether or not it exists as a single-phase material. It is revealed that GaCN is a composite, consisting of phase-segregated, nano-scale clusters of wurtzitic GaN polycrystals, in addition to inclusions of carbon, nitrogen and gallium, which are chemically bonded into several forms, but not belonging to the GaN crystals itself. By varying the deposition temperature between 400 and 600 oC, and the NH3 partial pressure between 0.7×10-3 and 7.25 mbar, layers with a wide compositional range of Ga, C and N are prepared.
关键词： composite thin films,atomic layer deposition,optical applications,GaCN,tuneable refractive index
更新于2025-09-09 09:28:46