Different Wavelengths Of Incident Light Research Articles

Design of a wide bandwidth achromatic metalens based on phase change material GST with aperture sharing

This paper proposes the use of aperture sharing synergistic operation in the structure of the metalens, together with the rational selection of the scattering unit size according to the linear relationship between the output phase and frequency of the scattering unit, and the selection of the slope of the phase variation with frequency, combined with the modulation of the phase change material Ge2Sb2Te5 crystallization rate m value, in the set wavelength band, for different wavelengths of incident light through the metasurface can produce a uniform phase distribution. The method is used to achieve a polarization-insensitive achromatic metalens in the 9.5-13 μm continuous wavelength band by adjusting the m value of the phase transition material Ge2Sb2Te5 crystallization rate and producing a phase distribution with a uniform focal length for different wavelengths of incident light passing through the metasurface. The simulation results show that the focal length of the achromatic metasurface varies by 3.57 μm in the working band, with an error of about 4.3% from the set focal length, and the full width of the half-peak of the focal point at all wavelengths of incidence reaches the diffraction limit, and the focusing efficiency exceeds 60%. The achromatic metalens proposed in this paper provides a new idea for the design of achromatic metasurfaces and promotes the research of phase change materials in broadband achromatic metasurfaces.

Study of transmission and reflection of hydrophilic transparent nano-titanium dioxide coating

Purpose The paper aims to design the optimum formulation of the nano-titanium dioxide (TiO2) hydrophilic coating system using the synthetic polypropylene glycol (PPG), which can create the reflection and absorption property. Design/methodology/approach TiO2 nanoparticles are used as fillers, and PPG has been blended at the proper ratio of 1PPG: 0.2TiO2. The prepared resin has been applied onto the glass substrate at different numbers of glass immersions during the dip-coating fabrication process. One-time glass immersion is labeled as T1 coating, two-time glass immersion is labeled as T2 coating and three-time glass immersion is labeled as T3 coating. All the prepared coating systems were left dry at ambient temperature. Findings T3 coating showed the lowest reading of WCA value at 40.50°, due to higher surface energy at 61.73 mN/m. The T3 coating also shows the greatest absorbance property among the prepared coating systems among the prepared coating. In terms of reflectance property, the T2 coating system has great reflectance in UV region and near-infrared region, which is 16.47% and 2.77 and 2.73%, respectively. The T2 coating also has great optical transmission about 75.00% at the visible region. Research limitations/implications The development of thermal insulation coating by studying the relationship between convection heat and reflectance at different wavelengths of incident light. Practical implications The developed coating shows high potential for glass window application. Originality/value The application of the hydrophilic coating on light absorption, reflectance and transmission at different wavelengths.

Trapping and sorting of nanoparticles by bowtie-nanohole plasmonic tweezers

Optical tweezers are a crucial tool for manipulating nanoscale objects, and have a wide range of applications in various fields. Bowtie-nanohole tweezers, a type of near-field optical tweezers, are particularly intriguing due to their strong near-field enhancement and unique characteristics. In this paper we provide a detailed discussion of the properties of bowtie-nanohole tweezers on trapping and sorting nanoparticles through theoretical and numerical results. It is discovered that the tweezers behave differently when trapping particles with varying refractive indices, leading to a discussion of sorting chiral particles. Moreover, the relative refractive index between the particles and the background solution greatly influences the trapping and sorting abilities of the tweezers. Finally, we investigate the performance of the tweezers at different wavelengths of incident light to determine the optimal working wavelength for trapping or sorting.

Linear and circular dichroisms of cholesteric liquid crystals in a longitudinal external magnetic field

ABSTRACT We investigated the properties of linear and circular dichroisms of cholesteric liquid crystal layer in external static magnetic field directed along helix axis. We showed that when the direction of light propagation and the direction of external magnetic field coincide, increasing the latter magnitude leads to a decrease in the linear dichroism, whereas when these directions are opposite, increasing the external magnetic field ( B e x t ) magnitude leads an increase in the linear dichroism. The presence of external magnetic field leads to the shift of circular dichroism curves both along wavelength axis and along dichroism axis. Then, we investigated the peculiarities of dichroism dependencies on B e x t for different wavelengths of incident light. We compared the dependence of circular dichroism on B e x t for a magnetically active cholesteric liquid crystal layer and an isotropic magnetically active layer and showed that while these dependencies are similar for wavelengths away from the photonic band gap, diffraction significantly affects these dependencies for wavelengths near and inside the photonic band gap. We investigated the evolution of spectra of linear and circular dichroisms at the change in B e x t , too. The results obtained can find application in the design of innovative polarised optoelectronic devices.

Enhancement of focusing properties of Bessel-like beam by metallic surface nanostructure

The focusing properties of a Bessel-like beam emitted from a circular slit surrounded by a surface groove (CSSG) were explored using experimental and numerical methods. The optical properties of the light emitted from the CSSG can be enhanced by using the scattered light from the surface groove. Furthermore, different modes of cylindrical surface plasmons in the circular slit are induced by different wavelengths of incident light, and beam shapes with a single spot and doughnut are created under illumination in the ultraviolet and visible regimes, respectively. A versatile beam shape is obtained from the CSSG structure.

Specific properties of light localisation in the cholesteric liquid crystal layer. The effects of layer thickness

ABSTRACT We investigated the effect of the thickness of the cholesteric liquid crystal (CLC) layer on the light energy and the density of the localised light energy in a CLC layer, as well as on the photonic density of states (PDS). It was shown that strong light localisation takes place on edge modes and that the amount of stored energy in the CLC layer depends on the value of refractive index of CLC layer surroundings. The dependences of the density of the localised light energy and PDS versus CLC layer thickness both for different wavelengths of incident light and edge modes are investigated. The effect of the thickness of the CLC layer on the total (integral) light energy and the density of the total localised light energy in the cholesteric liquid crystal (CLC) layer is discussed. It was shown that the total energy density is maximum for very small thicknesses of the CLC layer. We investigated the effect of the thickness of the CLC layer on absorption, the total field (aroused in CLC layer) amplitude, ellipticity and azimuth, too.

Sensitivity analysis of graphene multilayer based surface plasmon resonance biosensor in the ultraviolet, visible and infrared regions

The sensitivity of a gold–graphene-based surface plasmon resonance (SPR) biosensor with angle scanning was numerically analyzed in the ultraviolet, visible and infrared regions. By comparing the sensitivities of the proposed SPR biosensor for different wavelengths of incident light, we find that there is an optimal wavelength of incident light for the proposed SPR biosensor to achieve the highest sensitivity (called peak sensitivity) in the ultraviolet, visible and infrared regions. In addition, with the increases of the number of graphene layers, the optimal wavelength becomes larger (red shift), but the peak sensitivity increases first, and then decreases. When the number of graphene layers equals to 7, the maximum of peak sensitivity shows at 550 nm and reaches to 76.80°/RIU, which is 40% higher than the sensitivity at 630 nm (near a common-used wavelength 633 nm). Furthermore, the sensitivity decreases with the number of graphene layers increases at the wavelength less than 540 nm, while increases at the wavelength more than 570 nm. Moreover, the origin of sensitivity enhancement is also determined by analyzing the electric field intensity inside the proposed SPR biosensor.

Ag nanoprism metamaterial based tunable plasmonic logic gate

A metamaterial comprised of asymmetrically arranged Ag nanoprisms has been proposed and investigated in this paper. The metamaterial shows a polarization dependent PIT effect. The metamaterial with its periodic length along a y-axis less than 400 nm shows two tunable transmission dips. When the periodicity is increased above 400 nm, the metamaterial shows three adjustable transmission dips against the polarization state. By choosing different wavelengths of incident light, the metamaterial can be used as plasmonic Boolean logic gates. The working wavelengths of these plasmonic devices can then be adjusted by controlling the fillet radius of Ag nanoprism in metamaterial. These results offer great potential in developing polarization dependent tunable plasmonic information processing devices.

Plasmonic Circuit Theory for Multiresonant Light Funneling to a Single Spatial Hot Spot.

We present a theoretical framework, based on plasmonic circuit models, for generating a multiresonant field intensity enhancement spectrum at a single "hot spot" in a plasmonic device. We introduce a circuit model, consisting of an array of coupled LC resonators, that directs current asymmetrically in the array, and we show that this circuit can funnel energy efficiently from each resonance to a single element. We implement the circuit model in a plasmonic nanostructure consisting of a series of metal bars of differing length, with nearest neighbor metal bars strongly coupled electromagnetically through air gaps. The resulting nanostructure resonantly traps different wavelengths of incident light in separate gap regions, yet it funnels the energy of different resonances to a common location, which is consistent with our circuit model. Our work is important for a number of applications of plasmonic nanoantennas in spectroscopy, such as in single-molecule fluorescence spectroscopy or Raman spectroscopy.

Efficient photocatalytic hydrogen generation by Pt modified TiO2 nanotubes fabricated by rapid breakdown anodization

Photo-assisted hydrogen generation studies of platinum loaded titanium (IV) oxide nanotubes suspended in ethanol–water mixture were carried out at room temperature. The TiO2 nanotubes synthesized by rapid breakdown anodization technique were loaded with Pt nanoparticles by chemical reduction of aqueous chloroplatinic acid solution using sodium borohydride. The chemisorption (active) surface area of the synthesized nanocomposites for hydrogen was measured by pulse chemisorption method using temperature programmed desorption reduction oxidation equipment and found to decrease with increase in platinum loading in the range 1–10wt%. The platinum supported nanotube composites were characterized for phase and morphology by XRD, TEM and SEM. The hydrogen generated by the photocatalytic reduction of water from water–ethanol mixture at different wavelengths of incident light, using the Pt-TiO2 nanocomposite photocatalyst, was determined by using a proton exchange membrane based hydrogen meter. The highest hydrogen generation efficiency was observed at 1–2.5wt% of Pt loading. The maximum photocatalytic hydrogen generation of 0.03mol/h/g of Pt-TiO2 was observed with a 64W UV light source (λ=254nm). The photoluminescence property of the Pt loaded TiO2 has been correlated with the hydrogen generation efficiency and the reaction mechanism briefly discussed.

ChemInform Abstract: Photochemical Isomerization of Platinum(II) Complexes Containing Phosphine and Carbonyl Ligands: Pt(CO)(PR3)X2 (X: Cl, Br, I)

Abstract The photo-induced cis-trans isomerization of Pt(CO)(PR 3 )X 2 , where X=Cl, Br and I; PR 3 =PEt 3 , PMePh 2 and PPh 3 , has been studied in chloro-hydrocarbon solvents, with emphasis on the chloro-triethyl complexes. Photo-induced dimerization was a concurrent reaction to varying degrees for the complexes. In chloroform and carbon tetrachloride, an induction period was observed for isomerization. Addition of carbon monoxide enhanced isomerization but suppressed dimerization, while continuous purging with nitrogen produced the opposite effects. For cis -Pt(CO)(PEt 3 )Cl 2 , the quantum yield of cis-trans conversion was about 0.6 at different wavelengths of incident light; it was invariable towards the presence of oxygen or 1,3-pentadiene, but increased to about 0.8 in the presence of carbon monoxide introduced at different pressures. These results indicate that isomerization takes place from a singlet state of relatively long lifetime, with metal-carbonyl bond breaking as the first step, followed by catalysis of the reaction by the free ligand.

FDTD analysis of the light propagation in the cones of the human retina: an approach to the Stiles–Crawford effect of the first kind

In this work, we analyse the propagation of light in the human retinal cones by the finite-difference time-domain method (FDTD) in cylindrical coordinates, for systems with axial symmetry or body of revolution (BOR). This work constitutes a preliminary approach to the study of the Stiles?Crawford effect of the first kind (SCE I), as a cone has been simulated, while the SCE I is a consequence of a large number of photoreceptors. The FDTD method enables a numerical resolution of Maxwell's equations. With the computational implementation of these equations we have obtained, in the cone endface, the intensity patterns for different angles with which the light strikes the input side of the photoreceptor, and different wavelengths of incident light. In view of the results, the characteristics of fibre optics presented by the retinal cones remain valid, as does the goodness of the method and of the computational cone model that we have proposed. This work demonstrates, in short, the computational validity of our cone model as well as the power and versatility of the FDTD-BOR algorithm for the analysis and comprehension of the phenomenon of light propagation in retinal photoreceptors. It therefore offers broad possibilities in the field of research on visual processes, serving as support for analysis and interpretation of experimental measurements.

Photochemical isomerization of platinum(II) complexes containing phosphine and carbonyl ligands: Pt(CO)(PR 3)X 2 (X=Cl, Br, I)

The photo-induced cis-trans isomerization of Pt(CO)(PR 3)X 2, where X=Cl, Br and I; PR 3=PEt 3, PMePh 2 and PPh 3, has been studied in chloro-hydrocarbon solvents, with emphasis on the chloro-triethyl complexes. Photo-induced dimerization was a concurrent reaction to varying degrees for the complexes. In chloroform and carbon tetrachloride, an induction period was observed for isomerization. Addition of carbon monoxide enhanced isomerization but suppressed dimerization, while continuous purging with nitrogen produced the opposite effects. For cis-Pt(CO)(PEt 3)Cl 2, the quantum yield of cis-trans conversion was about 0.6 at different wavelengths of incident light; it was invariable towards the presence of oxygen or 1,3-pentadiene, but increased to about 0.8 in the presence of carbon monoxide introduced at different pressures. These results indicate that isomerization takes place from a singlet state of relatively long lifetime, with metal-carbonyl bond breaking as the first step, followed by catalysis of the reaction by the free ligand.