Refractive Index Values Research Articles

Extraction Study of Black Pepper (Piper nigrum l.) Using Ultrasound-Assisted Extraction Method

Piper nigrum l. or black pepper, is a plant native to Indonesia that grows in Malaysia, Sri Lanka, Vietnam, and other Southeast Asian countries. Black pepper is processed into oleoresin by extraction. Ultrasound-assisted extraction is a method to increase the yield and efficiency of oleoresin extraction. This study aimed to examine the effect of extraction time and temperature on yield, density, refractive index, study chemical components of black pepper oleoresin, and assess the best relative results according to SNI 01-0025-1987-B. Black pepper powder was extracted by ultrasound using ethanol solvent. The ratio of material and solvent used is 0.37 w/v. The operating conditions were carried out at extraction times of 20, 35, 50, 65, and 80 minutes and extraction temperatures of 30, 40, 50, 60, and 70 ˚C with a frequency of 40 kHz. The results showed that increasing the extraction time and temperature caused the yield, density, and refractive index values to be greater. The best relative results at 80 minutes and 70˚C with a dark brown color, in the form of a liquid paste, with a distinctive pepper aroma, yield 22.57%, density 0.8350 gram/ml, piperine content 74.78%, content 25.22 %, and a refractive index of 1.4900

Evaluation of characteristics of cajuput oil by steam-hydro distillation (Melaleuca leucadendra L.)

Cajuput oil is one of the types of essential oil that is most widely used by the society. Cajuput oil is obtained through a distillation process. The aim of this study was to determine the characteristics of cajuput oil. The raw material used is fresh cajuput leaves and the distillation process carried out is the steam-hydro distillation method. The characteristic analysis seen in this research includes yield of oil, water content of cajuput leaves, refractive index and sensory of the aroma and color of cajuput oil. The results showed cajuput oil with a yield value of 0.6%, water content of cajuput leaves of 64.36%, refractive index value of 1.470, aroma of cajuput leaves, and yellow color of cajuput oil. The characteristic of cajuput oil in this research was meet the Indonesian National Standard of cajuput oil.

Unveiling Local Optical Properties Using Nanoimaging Phase Mapping in High-Index Topological Insulator Bi2Se3 Resonant Nanostructures.

Topological insulators are materials characterized by an insulating bulk and high mobility topologically protected surface states, making them promising candidates for future optoelectronic and quantum devices. Although their electronic properties have been extensively studied, their mid-infrared (MIR) properties and prospective photonic capabilities have not been fully uncovered. Here, we use a combination of far-field and near-field nanoscale imaging and spectroscopy to study chemical vapor deposition-grown Bi2Se3 nanobeams (NBs). We extract the MIR optical constants of Bi2Se3, revealing refractive index values as high as n ∼ 6.4, and demonstrate that the NBs support Mie resonances across the MIR. Local near-field reflection phase mapping reveals domains of various phase shifts, providing information on the local optical properties of the NBs. We experimentally measure up to 2π phase-shift across the resonance, in excellent agreement with finite-difference time-domain simulations. This work highlights the potential of Bi2Se3 for quantum circuitry, nonlinear generation, high-Q metaphotonics, and photodetection.

Influence of the addition of WO3 on TeO2–Na2O glass systems in view of the feature of mechanical, optical, and photon attenuation

Abstract A study was conducted to investigate how the addition of WO3 affects the mechanical, optical, and photon attenuation properties of TeO2–Na2O glass systems. In this study, four glass systems categorized as W5, W10, W15, and W20 were studied to evaluate the impact of WO3 on TeO2–Na2O glass systems in view of the feature of mechanical, optical, and photon attenuation. The rising values of elastic moduli suggest that increasing WO3 on TeO2–Na2O glass systems makes the glassy structure more stable. Incorporating WO3 into TeO2–Na2O glass systems results in an increased energy band gap, rising from 2.83 to 2.95 eV. This phenomenon, in turn, leads to a decrease in the refractive index, dielectric constant, and optical dielectric constant values from 2.444 to 2.411, 5.975 to 5.811, and 4.975 to 4.811, respectively. While the linear attenuation coefficient (LAC) of the examined glass systems (W5, W10, W15, and W20) displayed a comparable pattern, the LAC value of glass sample W20 stood out as the highest among them. However, due to the addition of WO3 on the TeO2–Na2O glass system, at a lower energy region from 0.0284 to 0.06 MeV, there was a little variation among the mass attenuation coefficients of these glass systems studied herein, but a negligible variation was found from 0.662 to 2.51 MeV. The studied glass sample W20 with the highest amount of WO3 (20 mol%) on the TeO2–Na2O glass system displayed the lowest half-value layer. However, glass samples W5, W10, and W15 exposed 1.29, 1.07, and 1.03 times higher values of mean free path than W20. In addition, the values of the half-value layer were compared with the literature data of WO3–MoO3–TeO2, BaO–Li2O–B2O3, and CaF2–BaO–P2O5 glass systems. Studied glass sample W20 showed the maximum shielding performance from energy 0.284 to 2.51 MeV.

Judd–Ofelt Analysis and Spectroscopy Study of Tellurite Glasses Doped with Rare-Earth (Nd3+, Sm3+, Dy3+, and Er3+)

A series of glasses based on (80-y) TeO2-20 BiCl3-y RE2O3 (y = 0, 0.6 mol%; RE = Nd, Sm, Dy, and Er) were prepared. The thermal stability of the glass was determined by differential scanning calorimetry (DSC). The density and optical energy values of the prepared glass increased in the order of Sm2O3, Nd2O3, Dy2O3, and Er2O3. In addition, the glass doped with Er2O3 had the highest refractive index values compared to the other samples. Subsequently, Judd–Ofelt parameters (Ω2, Ω4, and Ω6) were obtained for the family of RE3+ trivalent rare-earth ions introduced as dopants in a tellurite glass. These parameters were calculated from the absorption spectra for each RE3+. The structures were studied by Raman spectroscopy deconvolution, which determined that TeO4, TeO3, TeO3+1, BiO6, and BiCl6 units had formed. In addition, the structural changes in the glass are related to the intensity ratio of TeO4/TeO3, depending on the type of rare-earth. For the optics and Judd–Ofelt parameters, the ray spectroscopy results of the prepared glass show that it is a good candidate for nonlinear optics fibers, a solid laser material.

Effect of TiO2/ZnO nanofillers on structural, optical and nonlinear optical properties of PVA

Polyvinyl alcohol (PVA)/(x)Titanium dioxide (TiO2) (15-x) Zinc oxide (ZnO) nanocomposites for x = 0, 1, 5, 7.5, 10, 14 and 15 wt% concentration was prepared using solution casting method with the help of an ultrasonicator. The XRD spectra of films validate the formation of nanocomposites, as evidenced by the presence of peaks corresponding to both PVA and TiO2/ZnO nanoparticles. FTIR spectroscopy reveals the formulation of complexes between the PVA main chain and nano fillers. The homogeneous distribution of nano fillers in PVA nanocomposites was observed using SEM and EDAX. The optical studies conducted using an ultraviolet–visible spectrometer reveals that PVA/(x)TiO2(15-x) ZnO shows minimum energy gap of 2.66 eV at x = 15 wt%. The photoluminescence measurements carried out at an excitation wavelength of 370 nm using spectrophotometer exhibits unique strong emission band at 680 nm in the visible region for all the films. The open aperture (OA) Z-scan traces of PVA filled TiO2–ZnO nanocomposites at various filling levels were explored by means of Z-scan technique with DPSS continuous wave laser at 532 nm wavelength and 200 mW output power reveals that the absorption coefficient (β) of PVA nanofilms rises from 3.19 × 10−5 cm/W (for pure) to 1.17 × 10−3 cm/W (for x = 14 wt %) with rise in filling level. The closed-aperture (CA) z-scan analysis gives the nature of third order nonlinear refractive index (NRI) (n2) of PVA nanofilms. The value of nonlinear refractive index (NRI) increases from −1.57 × 10−9cm2/W (pure PVA) to −3.24 × 10−8 cm2/W for x = 14 wt% filling level. The observed enhancement in Nonlinear absorption (NLA) coefficient (β), NRI (n2) and third order nonlinear susceptibility (χ3) of prepared nanocomposites is due to added nanofillers to the PVA matrix. The improved third order nonlinear optical properties make these PVA nanocomposites as good candidates for optical switching device and optoelectronic device applications.

Polarization-insensitive magnetically tunable perfect absorber for refractive index sensing applications

In this paper, a polarization-insensitive magnetic tunable perfect metamaterial absorber is analyzed which shows its functionality as a refractive index (RI) sensor. The unit cell structure of reported absorber consists of a cross-shaped Indium Arsenide (InAs) array over aluminum ground plane and has dimensions less than [Formula: see text] with thickness of 7.5[Formula: see text][Formula: see text] and periodicity of 9[Formula: see text][Formula: see text] making it an ultra-thin absorber. The proposed absorber provides an average absorption of 99.99% on the implementation of magnetic field (B) at 0.4[Formula: see text]T. The resonance frequency and corresponding absorption rates can be controlled by varying the magnetic field from [Formula: see text]–0.4[Formula: see text]T which provides high absorption as well as shift in the frequency spectrum by 0.3[Formula: see text]THz/T. Additionally, parametric analysis has also been done to confirm the selection of the optimum value of the designed parameters of the structure. Furthermore, simulation results reveal that the proposed structure is very sensitive to the change of RI values in the surroundings thus, the proposed structure can be employed as a RI sensor high sensitivity of 1.083[Formula: see text]THz/RIU over the range of 1–1.6[Formula: see text]RI. In addition, the result shows that the sensor can detect different chemical compounds such as ethanol, gasoline, paraffin, sodium chloride, carbon disulfide with an average sensitivity of 0.925[Formula: see text]THz/RIU. Thus, the proposed absorber with obtained sensitivity can be utilized as a biochemical sensor, making it one of the best contenders for chemical industry uses in diagnosis of different hazardous chemicals as well as finding its applicability in biomedical uses.

Optical Properties in Mid-Infrared Range of Silicon Oxide Thin Films with Different Stoichiometries.

SiOx thin films were prepared using magnetron sputtering with different O2 flow rates on a silicon substrate. The samples were characterized using Fourier transform infrared spectroscopy in transmission and reflection, covering a spectral range of 5 to 25 μm. By employing a multilayer model, the values of the complex refractive index that best fit the experimental transmission and reflection results were optimized using the Brendel-Bormann oscillator model. The results demonstrate the significance of selecting an appropriate range of O2 flow rates to modify the SiOx stoichiometry, as well as how the refractive index values can be altered between those of Si and SiO2 in the mid-infrared range.

Refractive index and volume fractions of various cellular components of plankton.

The refractive index (RI) of plankton, especially of live cells, has seldom been measured despite its critical role in determining the optical properties of phytoplankton and their effect on underwater light propagation. Here we present measurements of the RI of live cells representing several phytoplankton groups and ciliates collected from field and lab samples using a high precision holo-tomographic microscope, 3D Cell Explorer. The instrument was able to clearly differentiate three separate cellular structures according to their refractive index: membrane, chloroplast for phytoplankton (or cytoplasm for ciliate), and cytosol. RI values for membranes were distinct according to composition; for chloroplasts, were relatively conserved across phytoplankton taxa; and for cytosol, were close to that of seawater. The volumetric fractions of the membrane and chloroplast scale inversely with cell size whereas the volume of cytosol increased logistically. These results provide a more accurate measurement of RI and volume fractions of various cellular structures that can be used to improve optical modeling of marine plankton.

Determination of optical constants via the single oscillator Drude-Voigt dispersion model in fluoroborate glass for optical lenses: Nonlinear optical properties

In this work, a new fluoroborate (B2O3+AlF3+NaF + CaF2) glass has been fabricated using the melt-quenching technique. Glass sample has been characterized via X-ray diffraction, scanning electron microscope, and optical spectrophotometric measurements for absorption, transmission, and reflection in the range of 350–750 nm. The optical absorption of this transparent glass is used to determine the absorption coefficients, which are then used to estimate the extinction coefficients. The refractive indices as a function of wavelengths are estimated using extinction coefficients and reflectance data of fluoroborate glass. Very important parameters such as density, molar volume, and molar polarizability have been extensively studied. Using these data, fundamental optical parameters such as average oscillator strength (6.42) and inherent absorption wavelength (119 nm) are evaluated using the Drude-Voigt single oscillator model. Compared with previously studied oxide-based glasses, the fluoroborate glass possesses a relatively high refractive index of 1.74 and an Abbe number of 49 in the visible region of 587.6 nm. The relationship between inherent absorption wavelength and Abbe number values is also discussed. Moreover, the values of refractive index and linear optical susceptibility are used to evaluate the third-order optical susceptibility (11.56 × 10−14 esu) and nonlinear refractive index (2.50 × 10−12 esu). These results suggest that fluoroborate glass is a potential material for optical lenses and nonlinear devices in the visible range.

In-line open-cavity Mach-Zehnder interferometric refractive-index sensors based on inter-mode and inter-core-mode interferences

We experimentally demonstrated in-line Mach-Zehnder interferometric sensors based on inter-mode interference (IMI) and inter-core-mode interference (ICMI) for refractive index (RI) measurements. The structure of the IMI-based sensor consisted of a C-shaped fiber spliced between two multi-mode fibers (MMF) with the opposite ends spliced to lead-in and lead-out single-mode optical fibers. The ICMI-based sensor has a similar structure as the IMI-based sensor but with an additional in-house fabricated three-core multi-core fiber (MCF) spliced between the MMF and C-shaped fiber. The performance of the two RI sensors was evaluated and compared using water-glycerol solutions with RI values ranging from 1.333 to 1.338. The RI sensitivity, as well as other characteristic properties such as free spectral range and extinction ratio in relation to three lengths of the C-shaped fiber of 2, 2.5 and 3 mm, were investigated in both structures. The open-cavity characteristic of the C-shaped fiber allows the solution to interact with the optical path of the sensors, hence improving their RI measurement sensitivities. Both types of sensors exhibit linear wavelength responses with variation in RI. The RI sensitivity of the IMI-based sensor exhibits minor variations when the length of the C-shaped fiber is altered, with a maximum sensitivity of -7999.76 nm/RIU. In contrast, the RI sensitivity of ICMI-based sensor exhibits variability when changing the C-shaped fiber length, potentially due to variations in the RI distribution among the cores within the MCF, with its maximum sensitivity being -6211.98 nm/RIU. The temperature sensitivity of all the tested sensors was around 0.7 nm/ °C, denoting a low temperature cross-sensitivity of -7.427 × 10−5 RIU/ °C. This work experimentally exhibits a comparison of two sensing effects in the same configuration. The long length (longer than 2 mm) of the sensing element facilitates the fabrication process, and the open-cavity present in the proposed sensors yields a high sensitivity, which is in the same order of magnitude as the IMI-based sensors and is one order of magnitude higher than the ICMI-based sensors, emphasizing their promising candidacy for label-free optical sensing of chemical and biological samples.

Ultrafast optical characteristics of Mn-doped CdS quantum dots

Cadmium sulfide (CdS) quantum dots (QDs) doped with different concentrations of manganese (Mn = 0, 1, 3, 5, and 7 %) are synthesized via thermolysis of diselenocarbamato complexes of cadmium in the trioctylphosphine oxide (TOPO). The QDs show quantum size effects in the optical spectra and exhibit band-edge emission. The TEM images revealed that the QDs are spherical within the range of 3 to 5 nm. The nonlinear optical studies and optical limiting characteristics are studied. From open and closed aperture data, the nonlinear absorption coefficient (β) and refractive indices (n2) values are found to be in the range of 4–16 x10-9 cm2/w and 8-14x10-15 cm2/w. The cross relaxations and energy transfer mechanism of quantum dots are studied using the transient absorption pump–probe experiment.

Optical and microscopic characterizations of polyethylene oxides (PEO) doped with nickel nitrate (NiNO₃) transition metal salt

This study used a solution cast process to prepare a PEO doped with (4, 8 and 12 wt%) NiNO3 metal salt. Techniques including FTIR, optical microscope (OM), and UV–Visible-absorption spectrometry were employed to examine the structural, microscopic configuration and optical behaviors of the electrolyte. The FTIR bands indicated shifting and narrowing of PEO-O-H stretching bands by addition of 4w%NiNO3, suggesting a good interaction between the NiNO3 and the polymer. The optical microscope images showed the dark regions ascribed to amorphous phases and it is more dominant in the doped films than in the pure films. According to the optical absorption measurements optimum absorption and transmission of UV–visible light were observed at 4 wt% filler loading. Absorbance and transmittance of PEO were amplified by integrating 4 wt%NiNO3, although concentration above 4 wt% had insignificant influence on the optical behavior of PEO. The PEO:4w% NiNO3 films showed a higher value of refractive index and a greater optical conductivity in the UV wavelength which confirmed the presence of more charge carriers in the doped film. The regions attributed to band gap width and the different types of electron transitions were identified by using the Tauc's model in detail. The absorption edge shifting was distinguished for the 4 wt% doped PEO, and the optical band gap was reduced from 5.25 eV to 4.2 eV.

Frequency-dependent nonlinear optical response and refractive index investigation of lactone-derived thermochromic compounds

Nonlinear optical (NLO) switchable materials play a crucial role in the fields of electronics and optoelectronics. The selection of an appropriate switching approach is vital in designing such materials to enhance their NLO response. Among various approaches, thermos-switching materials have shown a 4-fold increase in NLO response compared to other photo-switching materials. In this study, we computationally investigated the geometric, electronic, and nonlinear optical properties of reversible lactone-based thermochromic compounds using the ωB97XD/6-311+G (d,p) level of theory. Molecular orbital studies are employed to analyze the electronic properties of the close and open isomers of these compounds, while time-dependent density functional theory (TD-DFT) analysis is utilized to evaluate their molecular absorption. Our findings reveal that the π-electronic conjugation-induced delocalization significantly influences the ON-OFF switchable nonlinear optical response of the lactone-based thermochromic compounds. Notably, among all compounds, the open isomer of lactone 2 exhibits the highest hyperpolarizability value (6596.69 au). Furthermore, we extended our analysis to investigate the frequency-dependent second and third-order hyperpolarizabilities. The most pronounced frequency-dependent NLO response is observed at 532 nm. Additionally, we calculated the refractive index of these thermochromic compounds to further assess their nonlinear optical response. The open isomer of lactone 1 demonstrates the highest refractive index value (3.99 × 10−14 cm2/W). Overall, our study highlights the excellent potential of reversible thermochromic compounds as NLO molecular thermos-switches for future applications.

Mesoporous aluminium titanate: Superhydrophilic and photocatalytic antireflective coating for solar glass covers with superior mechanical properties

In this study, the results of non-stoichiometric mesoporous aluminum titanate (mp-AlxTiOy) coating using sol-gel-based block copolymers assisted evaporation-induced self-assembly (EISA) have been presented. Here, a remarkably durable superhydrophilic coating with photocatalytic and anti-reflecting properties has been reported. With a Vicker's Hardness of 899 HV, mp-AlxTiOy coating on glass substrate indicates outstanding mechanical durability when exposed to the outside environment. Further, conventional accelerated ageing tests like the UV exposure test, damp-heat test, and saline resistance test were conducted to evaluate the endurance of the coating. By measuring the water contact angle, it has been proven that this coating is superhydrophilic. It has been shown through time-dependent degradation of (methylene blue, MB) dye; mp-AlxTiOy possesses photocatalytic capabilities similar to mp-TiO2. Additionally, the mp-AlxTiOy coatings were found to exhibit improved optical transmittance and a reduced refractive index value. The power gain of a conventional Si solar cell was finally studied by examining the I–V characteristics of mp-AlxTiOy coated glass coupons attached to the solar cell.

Anionic framework descriptors and microstructure affects on optical parameters of Ag7+x(P1-xGex)S6 single crystals

Herein we present a detailed study of single crystalline samples of Ag7+x(P1-xGex)S6 (x = 0, 0.1, 0.25, 0.33, 0.5, 0.75, 1) solid solutions. The Ag7+x(P1-xGex)S6 crystals were grown by directional crystallization from melt and characterized by techniques of XRD, Raman scattering, optical transmission measurements, spectral ellipsometry and electron microscopy. XRD and Raman scattering indicates a formation of solid solutions. The spectral dependences of refractive index are nonlinear with a maximum at the spectral range of ∼645–820 nm. It has been established, that P5+→Ge4+ cationic substitution leads to a monotonic nonlinear increase in the refractive index n from 2.58 (x = 0) to 2.75 (x = 1). The obtained values of refractive index were used to describe the optical parameters by the Wemple-DiDomenico equation. The spectral dependences of lnα at all studied temperatures (77–300 K) have an exponential shape near the absorption edge, indicating that they obey Urbach's rule. The corresponding value of the pseudo-gap Eg* and Urbach energy EU were determined. Increasing the Ge content in solid solutions causes a decrease in Eg* (1.971–1.466 eV) and EU (179.46–21.90 meV) values. Revealed Eg* values suggest that single crystalline Ag7+x(P1-xGex)S6 might be used as perspective solar harvesting materials. The practical application of these materials can be further enhanced with the results of temperature studies of variations of Eg* values. The changes in optical parameters are explained based on the structural and microstructural parameters of the studied solid solutions.

Synthesis, Surface Morphology, Gas Sensor, DSC Technique and Third-Order Behavior of Conducting Polymer.

The compound polyaniline (Poly-ANI) with different concentrations of (H2SO4) sulfuric acid has been synthesized by the chemical polymerization method. The prepared compounds have been characterized using number of techniques including FTIR, FE-SEM, EDS and DSC. Additionally, UV-Vis spectroscopy employed for studying the linear optical properties of polymer with different acid concentrations. Third order optical nonlinearity was characterized using Z-scan at 532nm. The results showed that the nonlinear refractive index has a negative sign. It was observed that the nonlinear refractive index changes in different ratios of H2SO4. The high value of nonlinear refractive index ( ) obtained along Z-axis is cm2/W, and the corresponding is 21.5 × 10-5 esu. Also, the Poly-ANI film shows the response to NH3 gas sensing in the range 20ppm-250ppm and can be used for NH3 sensing application.

Fast and Accurate Prediction of Refractive Index of Organic Liquids with Graph Machines.

The refractive index (RI) of liquids is a key physical property of molecular compounds and materials. In addition to its ubiquitous role in physics, it is also exploited to impart specific optical properties (transparency, opacity, and gloss) to materials and various end-use products. Since few methods exist to accurately estimate this property, we have designed a graph machine model (GMM) capable of predicting the RI of liquid organic compounds containing up to 16 different types of atoms and effective in discriminating between stereoisomers. Using 8267 carefully checked RI values from the literature and the corresponding 2D organic structures, the GMM provides a training root mean square relative error of less than 0.5%, i.e., an RMSE of 0.004 for the estimation of the refractive index of the 8267 compounds. The GMM predictive ability is also compared to that obtained by several fragment-based approaches. Finally, a Docker-based tool is proposed to predict the RI of organic compounds solely from their SMILES code. The GMM developed is easy to apply, as shown by the video tutorials provided on YouTube.

Influence of Gamma-irradiation on the Structural, Morphological, and Optical Properties of β-H2Pc Nanocrystalline Films: Implications for Optoelectronic Applications

Abstract In this study, the effects of gamma radiation with doses ranging from 0 KGy to 100 KGy on the structural and optical properties of the Beta Metal-free Phthalocyanine (β-H2Pc) powder and films were investigated. X-ray diffraction and scanning electron microscope were used to examine the crystalline and morphological structures of the thin films. While Fourier transform infrared and absorption spectra were utilized to study the changes in molecular structure and energy absorption, respectively. The results showed that while γ-irradiation induced changes in the surface morphology and optical properties of β-H2Pc, the molecular structure remained stable except for the disappearance of the hydroxyl (OH) functional group peak. The irradiation dose was found to affect the dielectric constants, dispersion characteristics, and nonlinear optical susceptibility of the material. The β-H2Pc thin films exhibited high absorption coefficients and refractive index values, making them promising candidates for optoelectronic devices such as solar cells. However, careful consideration of the effects of gamma irradiation on other properties of β-H2Pc such as stability, toxicity, and cost-effectiveness is necessary. Graphical Abstract

High-throughput computation and machine learning of refractive index of polymers

Refractive index (RI) of polymers plays a crucial role in the design of optoelectronic devices, including displays and image sensors. We have developed a framework for (1) high-throughput computation of RI values for computationally synthesized amorphous polymer structures based on a generalized polarizable reactive force-field (ReaxPQ+) model, which is orders-of-magnitude faster than quantum-mechanical methods; (2) prediction of composition–structure–RI relationships based on a machine-learning model based on graph attention neural network; and (3) computation of frequency-dependent RI combining ReaxPQ+ and Lorentz-oscillator models. The framework has been tested on a computational database of amorphous polymers.