Fabrication of UV-Curing Linalool-Polysiloxane Hybrid Films with High Refractive Index and Transparency

In this article,a series of high refractive indices(1.50-1.53)thiol phenyl polysiloxane(TPS)were synthesized via hydrolytic sol-gel reaction.The Fourier transform infrared spectra(FT-IR)and nuclear magnetic resonance spectra(NMR)results showed that TPS conformed to the predicted structures.Natural terpene linalool was exploited as photocrosslinker to fabricate UV-curing linalool-polysiloxane hybrid films(LPH)with TPS via photoinitiated thiol-ene reaction.LPH rapidly cured under UV irradiation at the intensity of 80 mW/cm^(2) in 30 s,exhibiting good UV-curing properties.The optical transmittance of LPH in the wavelength of 300-800 nm was over 90%,exhibiting good optical transparency.The water contact angle and water vapor permeability results showed that the introduction of phenyl groups enhance the hydrophobicity and water vapor barrier properties of LPH.The results indicated the potential of LPHs in the applications of optical functional coatings.

Predictive methods for density and refractive index of naphthenic lubricating oils during solvent extraction process

Lubricating oils are usually produced by solvent extraction to separate aromatics in order to achieve the desired specifications and better quality products.Among the different properties of lubricating oils,density and refractive index are some of the most important properties which can both be used for petroleum fluid characterization.Predictions of density and refractive index for naphthenic oils during solvent extraction by DMSO obtained by the pseudo-component approach and the quadratic correlation were both examined.The pseudo-component approach is a method to predict density and refractive index from composition while the latter merely relates density to refractive index.Results indicated that the predictions yielded by the pseudo-component method were in good agreement with experimental data for naphthenic oils.And the use of a function of refractive index(FRI_(20))as a pseudo-component property remarkably improved n_(20)predictions for the naphthenic mixtures.However,the density and refractive index predictions obtained by the quadratic correlation exhibited significantly higher de-viations for naphthenic oils than those for paraffinic oils.Thus a new modified correlation of the same functional form was proposed for naphthenic oils.The modification significantly improved predictions for naphthenic oils,which presented similar accuracy as the pseudo-component approach.And the previous correlation was still used for paraffinic oils.Additionally,effect of temperature on density and refractive index of naphthenic oils was examined.Results showed that the modified quadratic correlation was accurate for describing the relationship between density and refractive index of naphthenic oils at 20-90℃.The temperature dependence of density and refractive index for the raffinates and the extracts could be accurately described by the thermal coefficients for saturates and aromatics,respectively.Regarding the refractive index variation of the extracts with temperature,the empirical equation was proved to be a better option compared with the method using the thermal coefficient for aromatics.

Design of a coated thinly clad chalcogenide long-period fiber grating refractive index sensor based on dual-peak resonance near the phase matching turning point

A novel method for designing chalcogenide long-period fiber grating(LPFG) sensors based on the dual-peak resonance effect of the LPFG near the phase matching turning point(PMTP) is presented. Refractive index sensing in a high-refractive-index chalcogenide fiber is achieved with a coated thinly clad film. The dual-peak resonant characteristics near the PMTP and the refractive index sensing properties of the LPFG are analyzed first by the phase-matching condition of the LPFG. The effects of film parameters and cladding radius on the sensitivity of refractive index sensing are further discussed. The sensor is optimized by selecting the appropriate film parameters and cladding radius. Simulation results show that the ambient refractive index sensitivity of a dual-peak coated thinly clad chalcogenide LPFG at the PMTP can be 2400 nm/RIU, which is significantly higher than that of non-optimized gratings. It has great application potential in the field of chemical sensing and biosensors.

Highly sensitive fiber refractive index sensor based on side-core holey structure

We propose a side-core holey fiber （SCHF）-based surface plasmon resonance （SPR） sensor to achieve high refractive index （RI） sensitivity. The SCHF structure can facilitate analyte filling and enhance the overlapping area of the core mode and surface plasmon polariton （SPP） mode. The coupling properties of the sensor are analyzed by numerical simulation. The maximum sensitivity of 5000 nm/RIU in an RI range of 1.33-1.44, and the average sensitivity of 9295 nm/RIU in an RI range from 1.44 to 1.54 can be obtained.

Prediction of Density and Refractive Index of Lubricating Oils during Secondary Solvent Extraction Process by Furfural

To meet the requirements for high aromatic content and low polycyclic aromatic(PCA)concentration,eco-friendly aromatic-rich rubber extender oils are usually produced by two-stage solvent extraction processes with furfural.Among the different properties of rubber processing oils,density and refractive index are some of the most important properties related to their final quality.Two types of methods,including a pseudo-component approach by using mixing rules and several correlations,were used for calculation of density and refractive index at 20℃ of paraffinic furfural-extract oils and their secondary raffinates.Results indicated that similar accuracy was obtained for predicting the density and the refractive index of furfural+furfural-extract paraffinic oil systems.However,the quadratic correlation presents its advantage over the pseudo-component approach when the composition of oils is not available.Moreover,the quadratic correlation was also used for naphthenic lubricating oils during two-stage solvent extraction processes.The predictions showed much larger discrepancies with respect to experimental values than those of paraffinic lubricating oils,which indicated that the quadratic correlation was more suitable for paraffinic oils with a CN value of below 37%.

Cascaded tilted fiber Bragg grating for enhanced refractive index sensing

We proposed and experimentally demonstrated a cascaded tilted fiber Bragg grating（TFBG） for enhanced refractive index sensing. The TFBG is UV-inscribed in series in ordinary single-mode fiber（SMF） and reduced-diameter SMF with the same tilt angle, and then excites two sets of superposed spectral combs of cladding modes. The cascaded TFBG with total length of 18 mm has a much wider wavelength range over 100 nm and narrower wavelength separation than that of a TFBG only in the SMF, enabling an enlarged range and a higher accuracy of refractive index measurement. The fabricated TFBG with the merits of enhanced sensing capability and temperature self-calibration presents great potentials in the biochemical sensing applications.

The Approach of Compensation of Air Refractive Index in Thermal Expansion Coefficients Measurement Based on Laser Feedback Interferometry

We present the thermal expansion coefficient （TEC） measurement technology of compensating for the effect of variations in the refractive index based on a Nd： YA G laser feedback system, the beam frequency is shifted by a pair of aeousto-optic modulators and then the heterodyne phase measurement technique is used. The sample measured is placed in a muffle furnace with two coaxial holes opened on the opposite furnace walls. The measurement beams hit perpendicularly and coaxially on each surface of the sample. The reference beams hit on the reference mirror and the high-refiectivity mirror, respectively. By the heterodyne configuration and computing, the influences of the vibration, distortion of the sample supporter and the effect of variations in the refractive index are measured and largely minimized. For validation, the TECs of aluminum samples are determined in the temperature range of 29-748K, confirming not only the precision within 5 × 10-7 K-1 and the accuracy within 0.4% from 298K to 448K but also the high sensitivity non-contact measurement of the lower reflectivity surface induced by the sample oxidization from 448 K to 748 K.

High Refractive Index Ti3O5 Films for Dielectric Metasurfaces

Ti33O55 films are deposited with the help of an electron beam evaporator for their applications in metasurfaces. The film of subwavelength （632nm） thickness is deposited on a silicon substrate and annealed at 400℃. The ellipsometry result shows a high refractive index above 2.5 with the minimum absorption coefficient in the visible region, which is necessary for high efficiency of transparent metasurfaces. Atomic force microscopy analysis is employed to measure the roughness of the as-deposited films. It is seen from micrographs that the deposited films are very smooth with the minimum roughness to prevent scattering and absorption losses for metasurface devices. The absence of grains and cracks can be seen by scanning electron microscope analysis, which is favorable for electron beam lithography. Fourier transform infrared spectroscopy reveals the transmission and reflection obtained from the film deposited on glass substrates. The as-deposited film shows high transmission above 60%, which is in good agreement with metasurfaces.

Refractive index characteristics of edible oils based on spectrometry and effects of oil dispersion on OCT

It is necessary to investigate the wavelength-dependent variation rules of the refractive index of edible oils so as to explore the specificity of the dispersion in light propagation,imaging,and interference processes among different types of edible oil products.In this study,by deriving the refractive index equations of the double glass sheet holding device and oil,the reflectance spectra of three different types of oil samples,namely,peanut oil,colza oil,and kitchen waste oil,were measured via a spectrometer.Furthermore,the refractive index model of these different types of oil samples was investigated.Additionally,based on the oil dispersion characteristics,the dis-persion of oil in optical coherence tomography(OCT)was compensated via deconvolution.In the wavelength range of λ∈(380,1500)nm,the analytical expressions of the double glass sheet holding device and oils are featured by practical reliability.The refractive indexes of three different types of oils n∈(1.38,1.52)show normal dispersion characteristics.The Cauchy co-efficient matrix of the oil refractive index can be used for oil identification;in particular,the healthy oil and waste oil differ significantly in terms of the Cauchy coefficient matrix in the infrared band.Oil dispersion has almost no influence on the phase spectra of oils but can enhance their amplitude spectra.The dispersion mismatch can be eliminated by calculating the convo-lution kernel.The envelope broadening factors of OCT interference signals of oil products are 0.84,0.64,and 0.91,respectively.According to the present research results,the refractive index model of oil can effectively remove the influence of the holding device.The refractive indexes of three different types of oil samples show similar wavelength-dependent variation characteristics,which confirms the existence of many correlated components in these oil samples.The established refractive index model of oil in a wide spectral range,from the ultraviolet to the infrared band,can be adequately employed for identifying different types of oils.The numerical dispersion compensation based on the established refractive index model can enhance the axial resolution in OCT imaging.

Determination of Specific Refractive Index Increment (dn/dc)_μ at a Constant Chemical Potential,for Solutions of Polymer in Mixed Solvents by the GPC Method

A new chromatographic method is described for the determination of specific refractive index increment（dn/dc）μ at a constant chemical potential,for polymer/mixed solvent systems.In this method the（dn/dc）is obtained by measuring the areas of solvated-polymer peaks when the mixed solvent is used as an eluent.Values of（dn/dc）μ for the poly（dimethylsiloxane）（PDMS）-benzene-methanol system,determined by the proposed method are in good agreement with those determined by the conventional dialysis method.The new approach has the advantages of simplicity,fast speed,and high reproducibility.The experimental results for stearic acid-chloroform-methanol system show that this method can also be applied to nonpolymer/mixed solvent systems for the determination of（dn/dc）μ.

Band rules for the frequency spectra of three kinds of aperiodic photonic crystals with negative refractive index materials

By means of the theory of electromagnetic wave propagation and transfer matrix method, this paper investigates the band rules for the frequency spectra of three kinds of one-dimensional （1D） aperiodic photonic crystals （PCs）, generalized Fibonacci GF（p, 1）, GF（1,2）, and Thue Morse （TM） PCs, with negative refractive index （NRI） materials. It is found that all of these PCs can open a broad zero-n gap, TM PC possesses the largest zero-n gap, and with the increase of p, the width of the zero-n gap for GF（p, 1） PC becomes smaller. This characteristic is caused by the symmetry of the system and the open position of the zero-n gap. It is found that for GF（p, 1） PCs, the possible limit zero-n gaps open at lower frequencies with the increase of p, but for GF（1,2） and TM PCs, their limit zero-n gaps open at the same frequency. Additionally, for the tbree bottom-bands, we find the interesting perfect self-similarities of the evolution structures with the increase of generation, and obtain the corresponding subband-number formulae. Based on 11 types of evolving manners Qi （i = 1, 2,... , 11） one can plot out the detailed evolution structures of the three kinds of aperiodic PCs for any generation.

Refractive Index and Electronic Polarizability of Ternary Chalcopyrite Semiconductors

Simple models are proposed for the calculation of refractive index n and electronic polarizability α of AⅠBⅢC2Ⅵ and AⅡBⅣC2Ⅴ compounds of groups of chalcopyrite semiconductors from their energy gap data. The values family and 12 compounds of AⅡBⅣC2Ⅴ family are calculated for the work. The proposed models are applicable for the whole range of energy gap materials. The calculated values are compared with the available experimental and reported values. A fairly good agreement between them is obtained.

Effects of Phenyl Content and Molecular Structure on the Refractive Index of Organic Silicon Polymer

The effects of phenyl content and group distribution on the refractive index of phenyl silicone oil were investigated by synthesis and characterization of silicone oils of different molecular structures.A group contribution function model was established to predict the refractive index. The results showed that refractive index of phenyl silicone oil increased as its phenyl content increased. A linear equation had been established to describe the quantitative relationship between the refractive index and phenyl content.Refractive index values from the group contribution function model showed good consistency with experimental results.

Structure and Nonlinear Refractive Index of Bismuth Borate Glass

The method of conventional glass melting is used to study the glass formation region of Bi2O3-B2O3-TiO2-La2O3 system. The instrument of Differential Scanning Calorimeter （DSC） is used to research the glass stability. Raman spectra and IR spectra are used to speculate on the structure of glasses. The refractive index of glass is measured by prism coupler. With increase of Bi2O3, the glass stability, the amount of [BiO3] group and boron-oxygen loops decrease, while the content of B-O- bond, refractive index and nonlinear refractive index increase.

Measurement of Refractive Index Ranging from 1.42847 to 2.48272 at 1064 nm Using a Quasi-Common-Path Laser Feedback System

Wavelength 1064 nm is one of the most widely used laser wavelengths in industries and science. The high-precision measurement of the refractive index of optical materials at 1064 nm is significant for improving the optical design. We study the direct measurement of refractive index at 1064nm of lasers, including cMcium fluoride （CaF2）, fused silica and zinc selenide （ZnSe）, whose refractive indices cover a large range from 1.42847 to 2.48272. The measurement system is built based on the quasi-common-path Nd：YAG laser feedback interferometry. The thickness can be measured simultaneously with the refractive index. The results demonstrate that the system has absolute uncertainties of ~10-5 and ~10-4 mm in refractive index and thickness measurement, respectively.

Determination of Fructose and Glucose Contents in Honey by Liquid Chromatography-refractive Index Detection Method and Direct Titration Method

In this study, fructose and glucose contents in honey were determined by liquid chromatography-refractive index detection method and alkaline copper tartrate solution-direct titration method. According to the results, there were great differences between determination results of reducing sugar contents by liquid chromatography-refractive index detection method and alkaline copper tartrate solution-direct titration method. Specifically, average determination results of reducing sugar contents by liquid chromatography-refractive index detection method were reduced by about 9.5% compared with alkaline copper tartrate solution-direct titra- tion method. Subsequently, determination results of reducing sugar contents by two methods were compared and analyzed. Liquid chromatography-refractive index detection method was used to determine fructose and glucose monomers in honey, but alkaline copper tartrate solution-direct titration method was used to determine reducing sugar composition in honey, which might lead to significantly different results. Due to small sample size and limited conditions, the determination results were not necessarily representative. Bee product acquisition and processing enterprises and relevant departments should pay much attention on these issues and fully consider the current situation of grass-roots units to develop scientific, rigorous, simple, universal, convenient, low-cost and practicable standards, thus ensuring the safety and reliability of food quality.

Research Advances in Detection Techniques of High Performance Liquid Chromatography-Refractive Index Detector

As a highly sensitive and stable detector,refractive index detector is usually used for quantitative detection of substances such as polymer,sugar and organic acid. The research reviewed the application of HPLC-RID in the fields of quantitative determination of medicine and food,in order to lay a foundation for wider use of RID.

Temperature-induced effect on refractive index of graphene based on coated in-fiber Mach-Zehnder interferometer

The temperature-induced complex refractive index（CRI） effect of graphene is demonstrated theoretically and experimentally based on a graphene coated in-fiber MZI（Mach-Zehnder interferometer）. The relationships between real and imaginary parts of the graphene CRI and temperature are obtained through investigating the dip wavelength and intensity of the MZI interference spectrum changing with temperature, respectively. The temperature effect of CRI of the graphene is also analyzed theoretically. Both experimental and theoretical studies show that the real part and imaginary part of the CRI nonlinearly decrease and increase with temperature increasing, respectively. This graphene-coated in-fiber MZI structure also possesses the advantages of easy fabrication, miniaturization, low cost and robustness. It has potential applications in nanomaterial-based optic devices for communication and sensing.

FABRICATION OF TRANSPARENT PU/ZrO_2 NANOCOMPOSITE COATINGS WITH HIGH REFRACTIVE INDEX

Transparent ZrO2-polyurethane nanocomposites with high refractive index were prepared by dispersing ZrO2 nanoparticles in a polyurethane matrix via ligand molecule engineering. TEM showed that the inorganic particles were well dispersed within the polymeric network with no significant macroscopic agglomeration. By controlling the phase separation it was possible to obtain transparent zirconia nanostructured coatings, characterized by improved mechanical and thermal properties. UV-Vis spectra indicated that the coatings still maintained transparency in the visible light. The refractive index of the UV-cured films depends linearly on the ZrO2 content and varies from 1.475 to 1.625 （20 wt%） at 633 nm. These coatings could find advanced applications in coatings of optical and electronic devices.

Effect of Si δ-Doping on the Linear and Nonlinear Optical Absorptions and Refractive Index Changes in InAlN/GaN Single Quantum Wells

In the framework of effective mass approximation, we theoretically investigate the electronic structure of the Si δ-doped InAIN/GaN single quantum well by solving numerically the coupled equations Schrodinger-Poisson self-consistently. The linear, nonlinear optical absorption coefficients and relative refractive index changes are calculated as functions of the doping concentration and its thickness. The obtained results show that the position and the amplitude of the linear and total optical absorption coefficients and the refractive index changes can be modified by varying the doping concentration and its thickness. In addition, it is found that the maximum of the optical absorption can be red-shifted or blue-shifted by varying the doping concentration. The obtained results are important for the design of various electronic components such as high-power FETs and infrared photonic devices.