Different Values Of Refractive Index Research Articles

Multi-Wavelength Coherent-Perfect-Absorption−Laser Points and Half-Wave Phase Shift in Parity-Time-Reciprocal Scaling Symmetry Structure

Two slabs of dielectrics with different values of refractive index are synthesized to form a composite structure and the whole system satisfies parity-time-reciprocal scaling symmetry. Four coherent-perfect-absorber-laser points are induced by modulating the incident wavelength of lightwaves and the loss/gain factor of materials. The locations of coherent-perfect-absorber-laser points in parameter space, which manifests the multi-wavelengths of coherent-perfect-absorber-lasers could be regulated by the incidence angle. Especially, a value of π phase shift in the transmitted/reflected light wave has been observed as well. This research has potential applications in multi-wavelength absorbers/lasers and half-wave phase shifters.

Simple Method for Optical Detection and Characterization of Surface Agents on Conjugated Gold Nanoparticles.

In this article, we propose a simple method to calculate electrical permittivity and refractive index of surface agents of gold nanoparticles (Au NPs), in which it is possible to find the refractive index of surface agents shell by using the absorption peak of the gold nano-colloid. One of the usual tests for detection of surface agents is colorimetric methods based on the change of color of Au NPs. The color change is mainly due to the shift of localized surface plasmon resonance which is related to electrical interactions of surface agents. Although there are many mathematical models for simulating the absorption spectrum and calculating the plasmonic peak, using them is not simple and possible for everyone due to the need for programming. Here, the necessary simulations have been performed for different values ​​of refractive index of surface agents and particle size, and absorption peaks have been obtained. Using numerical methods, a simple formula is obtained between the wavelength of plasmonic peak, the ratio of hydrodynamic diameter to Feret size of the particles, and the refractive index of the surface agents. This method can help researchers to obtain the refractive index and consequently the type or concentration of surface agents around Au NPs without the need for programming or complex mathematical operations. It can also open new horizons in analyzing colorimetric diagnosis of biological agents such as viral antibodies, antigens, and other biological agents.

A Differential Intensity-Modulated Refractive Index Sensor Using a Droplet-Like Fiber Cascaded With FBGs

An intensity-modulated refractive index (RI) sensor based on a bending single-mode fiber (BSF) cascaded with fiber Bragg gratings (FBGs) is designed and experimentally investigated. The BSF structure can be easily fabricated by bending a section of single-mode fiber without coating, which is immersed in the RI matching solution. The different values of RI can be measured by monitoring the variation of the intensity difference of transmission dips of two FBGs. The experimental results show that the RI sensitivity of the proposed sensor is 413.23 dB/RIU in the sensing range from 1.333 to 1.371. In addition, the designed sensing system also shows a certain resistance to temperature cross-sensitivity and the fluctuation of light source, which can make a significant directive role in the field of food safety, biochemistry and environmental science.

Sensitivity Enhancement of Heterocore Macrobend Fiber Optics by Adding a ZnO Film

Optical fibers with high sensitivity are in demand due to their great potential in sensor application. Semiconductors, such as ZnO, are good materials. Using them as a second cladding offers opportunities in realizing next-generation multimaterial fiber optics. COMSOL Multiphysics is used to simulate heterocore macrobend fiber optics with the same curvature radius but different values of refractive index and thickness of ZnO films. The optimum thickness of ZnO films is identified by determining the loss of optical fibers. Macrobend heterocore fiber optics by adding ZnO thin film has been established by simulating and interpreting the relationship in terms of transmission and refractive index in the evanescent field. These results will provide a reliable fundamental to guide the performance in practice.

Improving the Efficiency of a Polymer Nanocomposite for Formation of Photon Structures by Means of Optical Recording

We present the results of investigation of conditions leading to optimization of an optical recording medium based on photosensitive urethane–acrylate nanocomposites containing silicone oxide nanoparticles that is used for efficient recording of Bragg gratings by means of multiple-beam interference. It is demonstrated that the choice of most efficient monomers and their concentration in the nanocomposite depending on their structure and the rate of polymerization, followed by finding optimal intensity of recording radiation for given composition, allows regulating the conditions for component diffusion thereby optimizing their redistribution in the recording medium and formation of regions with different values of refractive index. The results of the study can be used for creation of complex 2D and 3D photonic structures based on purposeful modification of light-sensitive polymer nanocomposites exhibiting various properties (luminescent, nonlinear-optical, etc.)

Splitting the bandwidth of a frustrated total internal reflection filter with nanoparticle inclusions

The frustrated total internal reflection (FTIR) spatial-frequency thin-film filter with metamaterial inclusions operating in a visible spectral range is investigated. Influence of nanoparticles embedded into a resonator layer is analyzed taking into account the frequency dispersion. Narrow band spectral lines and highly directional transmitted light beams for s- and p- polarizations are demonstrated at different values of refractive indices and thicknesses of layers. It is shown that the dispersion causes splitting of the filter bandwidth and spatial splitting of incidence beam into three angularly separated output beams. The type of thin-film filter considered should be useful in many applications, such as high-resolution spectroscopy and color imaging systems.

Vinyl ethers and epoxides photoinduced copolymerization with perfluoropolyalkylether monomers

New perfluoropolyalkylether (PFPAE) monomers, chain extended with different alkyl groups and functionalized with vinyl ether or epoxide end-groups, were employed, together with trimethylolpropane trivinyl ether or trimethylolpropane triglycidyl ether, to produce fluorinated copolymers. The photoinduced cationic polymerization was investigated, and the PFPAE-based copolymer properties were thoroughly characterized. Interesting surface properties and two different values of refractive index were observed: thus, these fluorinated copolymers can be suitable materials for the manufacture of self-cleaning coatings and optical waveguides.

Rectangular and sinusoidal Au-Grating as plasmonic sensor: A comparative study

Sensitivity of surface plasmon resonance sensor (SPRS) is mainly associated to efficient excitation of surface plasmon polaritons (SPPs) waves. In this work, effect of 50 nm thick Au film designed as rectangular and sinusoidal grating structure on glass substrate has been explored by finite element analysis (FEA) using COMSOL Multiphysics 5.3a. The comparison between the rectangular and sinusoidal gratings for efficient sensing has been presented here. Slit width (SW) for grating device has been optimized by applying far-field and near-field analysis while periodicity of grating structure is kept constant. Far field transmission spectra for both devices have been analyzed by illuminating the grating device through excitation port from the substrate side. Resonance wavelength (RW) dips for plasmonic grating device has been examined in each transmission spectrum for different values of refractive indices (RI). The sensitivity of plasmonic grating device has been calculated by measuring the shift in resonance wavelength by varying refractive index of analyte. The sinusoidal grating supporting fundamental plasmonic mode is found to be more sensitive (717 nm/RIU) as compared to simple rectangular grating (693 nm/RIU). Being highly sensitive to minute change in refractive index, such devices are efficiently applicable in real life.

Optimized conditions of Schlieren photography

Schlieren photography is a technique used to capture air movement based on differences in fluid density. Air with higher temperature has lower density than the surrounding air with lower temperature, leading to different values of refractive index. This work aimed to determine optimized conditions for schlieren photography to capture air movements in several situations. Schlieren photography was set up by using a single off-axis parabolic mirror with a 14.1cm diameter and a focal length of 131.2 cm. The air movement was captured in hi-speed mode with a Nikon V1 at 400 frames per second with a resolution of 640 × 240 pixels. The camera was set at ISO 400 at f/5.6 and used with a 70 − 300 mm zoom lens. Optimized conditions include percentage of light blocked by a knife edge, distance of test area to the mirror, illuminance of the light source, and ambient temperature.

Effect of negative permittivity and permeability on the transmission of electromagnetic waves through a structure containing left-handed material

We investigate the characteristics of electromagnetic wave reflection and transmission by multilayered structures consisting of a pair of left-handed material (LHM) and dielectric slabs inserted between two semi-infinite dielectric media. The theoretical aspect is based on Maxwell's equations and matching the boundary conditions for the electric and magnetic fields of the incident waves at each layer interface. We calculate the reflected and transmitted powers of the multilayered structure taking into account the widths of the slabs and the frequency dependence of permittivity and permeability of the LHM. The obtained results satisfy the law of conservation of energy. We show that if the semi-infinite dielectric media have the same refractive index and the slabs have the same width, then the reflected (and transmitted) powers can be minimized (and maximized) and the powers-frequency curves show no ripple. On the other hand if the semi-infinite dielectric media have different values of refractive indices and the slabs have different widths, then under certain conditions the situation of minimum and maximum values of the mentioned powers will be reversed.

Tunable nanoswitches based on nanoparticle meta-molecules

We introduce ultra-fast tunable nanoswitches based on the transition between states ofnanoparticle meta-molecules. These molecules are formed (activated) when hybrid systemsconsisting of metallic nanoparticles and semiconductor quantum dots interact withcoherent light sources (laser fields). The switching process occurs via minuscule changes ofthe refractive index of the environment or the distance between the quantumdots and metallic nanoparticles. These changes stimulate the transition betweenthe states of the meta-molecules in nanosecond timescales, setting up dramaticoptical events that can be observed easily. These nanoswitches can be tuned byvarying the intensity of the activating laser field, allowing us to adjust the switchingprocess to occur at different values of refractive indices. The results open a newhorizon for chemically, biologically, or physically triggered optical nanoswitchesand nanosensors that are sensitive to ultra-small changes in the environment.

Frustrated-total-internal-reflection-based thin-film color separator

The frustrated-total-internal-reflection thin-film color filtering device operating in a visible spectral range is designed. Such a device splits an incident light beam into spatially separated red, green, and blue color beams. Spectral shape and angular spread of transmitted light for s and p polarizations are calculated at different values of refractive indices and thicknesses of layers.

Spectrophotometric determination of iron and boron in soil extracts using a multi-syringe flow injection system

In the last decade, significant advances in flow analysis have been reported, namely the extensive use of computer-controlled devices to enhance the autonomy and performance of analysers. In the present work, computer-controlled multi-syringe flow injection systems are proposed to perform the spectrophotometric determination of available iron and boron in soil extracts. The methodologies were based on the formation of ferroin complex (determination of iron) and azomethine-H reaction (determination of boron). Both determinations were performed in manifolds with similar configurations by changing the reagents present in the different syringes. In the determination of iron, elimination of Schlieren effect in the detection system was achieved through the binary sampling approach, where a three-way valve was actuated to intercalate small slugs of sample and reagent, promoting better mixing conditions for solutions with different values of refractive index. In the determination of boron, in-line sample blank measurement was attained by omitting the introduction of reagent through software control, without manifold reconfiguration. Linear calibration curves were established between 0.50 and 10.0 mg Fe l −1 and between 0.20 and 4.0 mg B l −1. No systematic difference was found when soil extracts were analysed by the proposed methodologies and compared to the respective reference procedures.

EFFECTS OF FRESNEL AND DIFFUSED REFLECTIVITIES ON LIGHT TRANSPORT IN A HALF-SPACE MEDIUM

Radiation transfer problem for isotropically scattering, non-absorbing half-space medium with angular-dependent (specular) and constant diffuse reflecting boundary is considered. The angular-dependent reflectivity of the boundary is considered as Fresnel’s reflection probability function. Some physical and engineering quantities of interest such as angular distribution of radiation, total density of radiation and extrapolated endpoint are computed for various values of refractive index and diffuse reflecting coefficient using variational method. For sake of comparisons, results with average and effective reflectivities are carried out for different values of refractive indices. Our results for non-diffuse reflectivity are compared with the available data given for specular Fresnel’s reflectivity which show excellent agreement.

A design method for dielectric multilayer optical filters

A generalized design method for an optical filter consisting of a dielectric multilayer structure is proposed to get an arbitrary profile of the wavelength dispersion of reflectivity or transmittance. The basic concept of the method lies in the fact that the wavelength dispersion of the reflectivity is approximately determined by taking the inverse Fourier transformation of the refractive index profile of the multilayer structure. Construction of a filter with only three different values of refractive index is described.

Kerr enhancement by SiO and AlN films sputtered on plastic substrates

It has been found that there is a remarkable difference of Kerr enhancement effect between films sputtered on glass and on plastics. SiO film does not show so clear enhancement on plastics while it does on glass. Dependence of Kerr rotation angle Θk on SiO film thickness was compared with calculated Θk for different values of refractive index n, and the decrease of n was found on plastics. Also surface roughness was observed on plastics. On the other hand, AlN film shows fairly well enhancement even on plastics as well as on glass. There is no decrease of n, and smoother surface was observed. To obtain enough enhancement, many factors should be optimized.

The scattering of light by particles suspended in a medium of higher refractive index

A short review of the theoretical as well as experimental work done on the scattering of light by particles suspended in a medium of lower refractive index is given. Using the formula derived by Mie, calculations are extended to the case of particles such as air bubbles suspended in a medium of higher refractive index. Results are obtained for three different values of refractive indices and for three different sizes of the particles. When the particles are small in size, the distribution of intensity is symmetrical about the plane perpendicular to the incident beam. As the size of the particle increase, the intensity in the forward direction becomes greater than that in the backward direction. The angle of maximum polarisation is displaced from 90° in the direction of the incident rays and moreover, it is everywhere incomplete. Experimental observations are also made in the case of water particles dispersed in benzene.