Determination Of Refractive Index Research Articles

Refractive Index and Extinction Coefficient of Vapor-deposited Water Ice in the UV–vis Range

Abstract Laboratory results of the optical properties of vapor-deposited water ice, specifically the refractive index and extinction coefficient, are available mainly for a selective set of wavelengths and a limited number of deposition temperatures. Experimental limitations are the main reason for the lack of broadband data, which is unfortunate as these quantities are needed to interpret and predict astronomical and planetary observations. The goal of this work is to address these lacking data, using an experimental broadband method that is capable of rapidly providing reliable water ice data across the entire UV–visible range. This approach combines the simultaneous use of a monochromatic HeNe laser and a broadband Xe-arc lamp to record interference fringes of water ice during deposition at astronomically relevant ice temperatures. The ice thickness is typically more than 20 μm. Analyzing the period and intensity patterns combining both the monochromatic and broadband interference patterns allows the determination of the wavelength-dependent refractive index and extinction coefficient. We present accurate refractive index and extinction coefficient graphs for wavelengths between 250 and 750 nm and ices deposited between 30 and 160 K. From our data, we find a possible structural change in the ice in the 110–130 K region that has not been reported before. We also discuss that the data presented in this paper can be used to interpret astronomical observations of icy surfaces.

Ultra-precise determination of thicknesses and refractive indices of optically thick dispersive materials by dual-comb spectroscopy.

Precise measurements of the geometrical thickness of a sample and its refractive index are important for materials science, engineering, and medical diagnosis. Among the possible non-contact evaluation methods, optical interferometric techniques possess the potential of providing superior resolution. However, in the optical frequency region, the ambiguity in the absolute phase-shift makes it difficult to measure these parameters of optically thick dispersive materials with sufficient resolution. Here, we demonstrate that dual frequency-comb spectroscopy can be used to precisely determine the absolute sample-induced phase-shift by analyzing the data smoothness. This method enables simultaneous determination of the geometrical thickness and the refractive index of a planar sample with a precision of five and a half digits. The thickness and the refractive index at 193.414 THz (λ = 1550 nm) of a silicon wafer determined by this method are 0.5204737(19) mm and 3.475625(58), respectively, without any prior knowledge of the refractive index.

Determination of the Complex Refractive Index and Extinction Coefficient of Graphene Aerogel in the Infrared Band by Spectroscopy

Determination of the Complex Refractive Index and Extinction Coefficient of Graphene Aerogel in the Infrared Band by Spectroscopy

Analysis of the temperature component of the combined standard uncertainty of the refractive index according to the test data of the control system for meteorological parameters developed for the Lyptsi geodetic polygon

The National Scientific Centre “Institute of Metrology” is actively involved in the implementation of a number of international projects under the EMPIR programme. One of such joint projects is the EMPIR 18SIB01 GeoMetre research project “Large-scale dimensional measurements for geodesy”. The overall goal of the project is to ensure traceability of length measurements – from the measurement standard of the unit of length to long distances typical for geodetic measurements. As a result of the project, it is necessary to provide length measurements of at least 5 km with an expanded uncertainty of no more than 1 mm.
 The main task of the NSC “Institute of Metrology” within this project is the development, research and practical implementation of methods and means of accounting for the influence of the earth’s atmosphere on the results of measurements of long distances in geodesy, carried out using electromagnetic waves in the optical range.
 When performing the section Task 1.4 of the project, new methods of highly accurate determination of the mean integral refractive index of air, used as a correction taking into account the influence of the atmosphere on the measurement results, are justified. Requirements for the accuracy of measurements of meteorological parameters at discrete points of the baseline are formulated, which are necessary to determine the mean integral refractive index. That is, the requirements for the metrological characteristics of temperature, pressure and humidity sensors are determined.
 The article discusses the results of the development, manufacture and testing of the sensors for temperature measurement. It is shown that the created sensors meet the requirements of the GeoMetre project.

اصطناع بوليميرات آزو ببلمرة مشتاقات إيتيرية لبروميد الآليل ودراسة فجوتها الطاقية وتعيين بعض خصائصها الفيزيائية

في هذا البحث، اُصطنع مشتقان ايتريين لاصبغة ازو فينولية عن طريق تفاعل ويليمسون وفقاً لآلية. الاستبدال النيكلوفيلي SN2. تمت بلمرة المركبات المحضرة بلمرةً جذرية باستخدام (AIBN) كبادئ وأُثبتت بنى المركبات المصطنعة بواسطة مطيافيات FT-IR و 1H-NMR. بالإضافة إلى دراسة الخصائص الحرارية للبوليميرات المُحضرة بواسطة (DSC). دُرست عرض الفجوة الطاقية وذلك لمعرفة امكانية استعمال البوليميرات كأنصاف نواقل ضوئية وكانت قيمتها 2.4ev, 2.8ev لكل من P(AO2) و P(AON1) على التوالي. كماعُينت كل من قرينة الانكسار واللزوجة الكيناميكية والكثافة ودرجة العكارة.

Use of virtual laboratory PhET for organization and conduct of independent physical experiment

The article, on the example of laboratory work on optics "Determination of refractive index of glass", highlights the possibilities of using a virtual laboratory PhET for independent experimental activities of students. Possibilities of expanding the range of physical experiments on the topic of studying and implementing a differentiated approach to their conduct are revealed. The expediency of using virtual laboratories for conducting an experiment at a higher level, comparing the results and thus creating opportunities for more accurate determination of the studied parameters is shown. The advantages of combining real and virtual experiment in the complex formation of conscious knowledge and practical skills are outlined.

Surface plasmon resonance chemical sensor composed of a microstructured optical fiber for the detection of an ultra-wide refractive index range and gas-liquid pollutants

A surface plasmon resonance (SPR) chemical sensor comprising microstructured optical fiber (MOF) is designed for refractive index (RI) sensing in the visible to near-infrared (0.42-1.60 µm) region (NIR) as well as detection of gas-liquid pollutants. To realize mode coupling and facilitate manufacturing, gold with inert and plasmonic properties and an analyte sensing layer are introduced to the external surface of the MOF. The sensor is analyzed by the full-vector finite element method (FEM) and the wavelength and amplitude interrogation methods are adopted to evaluate the sensing characteristics. Our analysis reveals a maximum wavelength sensitivity (WS) of 15,000 nm/RIU, amplitude sensitivity (AS) of 1,603.37 RIU-1, and resolution (R) of 6.67×10−6 RIU in the determination of analyte RIs spanning an ultra-wide range between 1.00 and 1.45. Furthermore, the figure of merit (FOM) and signal-to-noise ratio (SNR) of the sensor are 295.01 RIU−1 and 2.95, respectively. On account of its simple structure, low cost, and industrial compatibility, this multi-functional sensor has tremendous potential in the chemical industry, environmental monitoring, and safety control such as harmful gas monitoring, industrial wastewater and domestic sewage detection.

Refractive index of phosphate-buffered saline in the telecom infrared C + L bands

The refractive index of phosphate-buffered saline (PBS) solutions, for concentrations ranging from 0 mol/L to 1.516 mol/L, was experimentally determined in the telecom C + L infrared bands, ranging from 1510 to 1620 nm, which is commonly used for silicon photonics biochemical sensors. The infrared measurements were performed with a silicon photonics arrayed waveguide sensor and compared with the optical visible range values measured with a handheld refractometer. An equation for the refractive index of PBS solutions as a function of wavelength and PBS concentration is presented. Moreover, the conductivity of the test solutions was determined and the relation between conductivity and refractive index was established, allowing for a fast, easy, cost-effective, indirect method of refractive index determination of PBS solutions. The data presented will enable more realistic simulation of optical biosensors and their precise experimental calibration.

Multiple solution solving in plasmon sensing by deep learning: determination of a layer refractive index and thickness in one experiment.

Plasmons have received intensive attention owing to their significant spectrum shift in environmental sensing. Experimentally, the same spectral shifts may be caused by different combinations of structural parameters of a plasmonic nanoparticle. This multi-parameter problem cannot be solved by just a single feature analysis, but requires using the full scattering spectrum containing all features of the parameters. In this Letter, a deep learning method for solving multi-parameter problems is proposed based on the layer refractive index (n) and layer thickness (d) sensing of different nanorods and nanospheres. The full scattering spectrum can be theoretically simulated, precisely predicted using a well-trained deep learning method, and experimentally obtained using a homemade dark-field microscope. An error analysis of the simulation and experimental results indicates that this method is a potential way to determine n and d and further solve multi-parameter in plasmon sensing.

(Invited) Complex Relative Permittivity of UV-C Transparent AlN

The optical absorption coefficients of high-quality 2-inch AlN substrates grown by physical vapor transport (PVT) were accurately calculated from transmittance and absolute reflectance measurements in the ultraviolet-visible (UV-Vis) range. Spatially uniform UV absorption coefficients of 13-23 cm-1 at 4.68 eV (265 nm) were demonstrated. This approach also provided accurate values for the reflection coefficients, allowing a determination of the complex refractive index and relative permittivity, which showed good agreement with previous reports. Values for the high-frequency and static permittivities obtained in this study were 4.22 and 7.84, respectively. The data specific to PVT AlN substrates obtained using this method are useful in the design of electronic and optoelectronic devices grown on these substrates.

Determination of thickness and refractive index of SiO2 thin films using the cross-entropy global optimization method

Silicon dioxide (SiO2) is a material that is abundant in nature and has wide application in semiconductor and insulating devices. In this work, a set of six SiO2 samples were grown on a Sigma-Aldrich Silicon substrate, varying the growth time and temperature. This set of samples were grown using times of 10 and 12h and temperatures of 800, 900, and 1000 ºC, under ambient atmosphere. After film growth, reflectance measurements were performed on the films and the substrate, using the Stellarnet UV-VIS-NIR spectrophotometer between 194 and 1081.5 nm. These measurements were modeled using a global optimization method, called Cross-entropy, together with the Bootstrapping resampling technique, seeking to robustly and statistically determine the thin film refractive index as a function of the wavelength and its thickness. To estimate the refractive index of the SiO2 thin film, the Cauchy model was used. For the substrate, reflectance measurements were used. The method proved to be efficient, presenting thickness values that were validated according to growth parameters and literature data. This method proved to be an important and low-cost tool, compared to traditional methods, to help in the steps of building thin films for semiconductor and insulating devices, thus improving their physical properties and enabling the development of new devices.

Simultaneous determination of thickness and refractive index using Cauchy or Sellmeier formulas by the example of surface plasmon resonance study on ultrathin polysulfone film

A three-wavelength method based on Cauchy or Sellmeier formulas is proposed for simultaneous determination of the thickness and refractive index without using approximate expansions of the refraction index over the wavelength. The method is also applicable for the simultaneous determination of other optical characteristics together with the refractive index. To test the applicability of the proposed method, the refractive index and thickness of ultrathin polysulfone film were obtained in the surface plasmon resonance experiment.

Simultaneous Determination of Refractive Index and Thickness of Submicron Optical Polymer Films from Transmission Spectra.

High-transparency polymers, called optical polymers (OPs), are used in many thin-film devices, for which the knowledge of film thickness (h) and refractive index (n) is generally required. Spectrophotometry is a cost-effective, simple and fast non-destructive method often used to determine these parameters simultaneously, but its application is limited to films where h > 500 nm. Here, a simple spectrophotometric method is reported to obtain simultaneously the n and h of a sub-micron OP film (down to values of a few tenths of a nm) from its transmission spectrum. The method is valid for any OP where the n dispersion curve follows a two-coefficient Cauchy function and complies with a certain equation involving n at two different wavelengths. Remarkably, such an equation is determined through the analysis of n data for a wide set of commercial OPs, and its general validity is demonstrated. Films of various OPs (pristine or doped with fluorescent compounds), typically used in applications such as thin-film organic lasers, are prepared, and n and h are simultaneously determined with the proposed procedure. The success of the method is confirmed with variable-angle spectroscopic ellipsometry.

Simulation for Enhancement in Sensitivity of Chalcogenide Glasses-Based Fibre Optic Evanescent Absorption Sensor for Malignant Tissue Detection

Background: Refractive index determination of biological tissues is a challenging issue. Many biological species also show vibrational signature in the infrared domain. The chalcogenidebased glasses can be used to make the fibree optic evanescent wave sensors for the detection of the analyte. Objectives: The primary objective is to study the effect of various parameters on the sensitivity of chalcogenide glass-based evanescent-wave sensor for biological tissue detection. Methods: An evanescent wave sensor has been proposed with collimated source illumination and uniform tapering. The chalcogenide materials are chosen such that the weakly guiding approximation could be followed. Complex refractive indices of liver tissue samples have been taken for the analysis of sensitivity via the method of the evanescent absorption coefficient. Equations for sensitivity have been solved analytically using MATLAB software. Results: The simplification of the formula for sensitivity leads to the inference that the sensitivity is a function of core radius, refractive indices of sample tissues and wavelength used. Moreover, since the refractive indices of the materials are also a function of temperature, therefore a change in temperature results in a change in the profile of guiding mode. Hence, the effect of temperature must also be observed. The initial simulation parameters are taken; core radius 100 μm, sensing length 4 cm and wavelength 1.0 μm. In the NIR region, we have a better sensitivity of detection for all the tissue samples and the risk of photodamage of the bio-samples is reduced to a good extent. It has been found that sensitivity decreases with wavelength and core radius, whereas increases with temperature. It has also been shown that sensitivity is found to be better with collimated in comparison with the diffused source. Conclusion: The comparative study results that one should operate at a shorter NIR region of wavelength for higher sensitivity. The collimated source illumination should be preferred over diffused one for launching the light within the fibree to have high sensitivity. Further, the length of the sensing region should be larger, but the fibree core radius should be smaller. The proposed biosensor is robust and can also be used many times if the probe (sensing region) is cleaned properly. Moreover, a small amount of analyte is enough for detection. Thus, the proposed sensor is very useful for biomedical applications with its high performance, accuracy and robustness.

Analytical determination of the complex refractive index and the incident angle of an optically isotropic substrate by ellipsometric parameters and reflectance.

An analytical solution for the determination of both angle of incidence (AOI) and the complex refractive index from combined ellipsometric and reflectometric measurements at optically isotropic substrates is presented. Conventional ellipsometers usually measure flat surfaces because the curvatures of the surface alter the reflected or transmitted light, which causes experimental errors due to the deviation of the incident angle. However, in real industrial applications, the shapes of samples are usually curved or even free-form. In this case, the knowledge of the AOI is essential. The proposed method provides a simple way to measure the AOI and the complex refractive index of nonplanar samples without extra or complicated hardware.

Investigation of a high-sensitivity surface plasmon resonance sensor based on the eccentric core quasi D-shape photonic quasi-crystal fiber

A highly sensitive refractive index (RI) sensor based on the surface plasmon resonance (SPR) phenomenon is proposed and demonstrated. The sensor is composed of a quasi D-shape ten-fold photonic quasi-crystal fiber (PQF) and indium tin oxide (ITO) film. The quasi D-shape and eccentric core structure strengthen coupling between the core mode and surface plasmon polariton (SPP) mode to enhance the sensing sensitivity, while the mechanical strength of the PQF is preserved. The properties of the sensor are determined numerically and optimized by the finite element method. In the RI range of 1.40–1.44, the maximum wavelength sensitivity and average wavelength sensitivity are 62,000 nm/RIU and 26,500 nm/RIU, respectively. Meanwhile, the loss spectra show smaller full-width at half-maximum and maximum FOM of 542.5 RIU−1. This novel sensor which boasts ultra-high-sensitivity and excellent FOM has large potential in the determination of liquid RIs.

Determination of the refractive index and wavelength-dependent optical properties of few-layer CrCl within the Fresnel formalism.

SummaryBased on previous reports on the optical microscopy contrast of mechanically exfoliated few layer CrCl3 transferred on 285 nm and 270 nm SiO2 on Si(100), we focus on the experimental determination of an effective mean complex refractive index via a fitting analysis based on the Fresnel equations formalism. Accordingly, the layer and wavelength‐dependent absorbance and reflectance are calculated. Layer and wavelength‐dependent optical contrast curves are then evaluated demonstrating that the contrast is significantly high only around well‐defined wavelength bands. This is validated a posteriori, by experimental UV‐Vis absorbance data. The present study aims to show the way towards the most reliable determination of thickness of the 2D material flakes during exfoliation.

An Improved Method for Determination of Refractive Index of Dielectric Films from Reflectance Spectrum by Using the Generalized Morse Wavelet

Abstract The Generalized Morse Wavelet (GMW) algorithm was adapted to determine the refractive index of dielectric film from the reflectance spectrum. A theoretically generated reflectance spectrum in the range of 300-1200 nm wavelength was analyzed by the Continuous Wavelet Transform (CWT) and the refractive index dispersion was obtained by the mentioned method. In addition, a noisy reflectance spectrum was analyzed to show the advantages of the CWT method. Refractive index dispersions calculated by the Morlet and the Paul wavelet were compared to GMW at the end of the study.

Comprehensive Study and Experimental Validation of U-shaped Probe Extrinsic Fiber Optic Sensor for the Measurement of Refractive Index at Various Temperatures using a Tunable Light Source

Extensive detection performances due to sensitivity to external and internal perturbations in the fiber structure makes the optical fiber sensors highly superior over the conventional sensors. The fiber optic sensors with clad removed fibers at some portion along its length play a vital role in the determination of refractive index of various liquids at several wavelengths and at several temperatures. In the present paper a refractive index sensor has been developed to investigate the performance and experimental validation in the measurement of R.I. values of liquids at various temperatures using a tunable light source capable of emitting light at the wavelengths of 630nm, 660nm, 820nm and 850nm. The U-shaped glass probe connected between the tunable light source and an optical detector using two multimode PCS fibers of 200/230μm, acts as a clad removed portion of the sensor which is called as sensing zone or sensing region. In the working principle of the sensor, the U-shaped glass rod immersed into each mixture prepared with the combination of Toluene and Acetonitrile, the light launched from the source reaching the detector was noted at various temperatures and by tuning the wavelength of the source to 630nm, 660nm, 820nm and 850nm. From the data obtained, the sensor was calibrated to measure the refractive index of various liquids at different temperatures and wavelengths. Exploiting all the advantages offered by the fiber optic communication systems, the sensor was expected to be rugged, robust, reliable, and durable offering the sensitivity in the range of the order of 10-5.

Determination of refractive index on three mediums based on the principle of refraction of light

This study aims to develop a tool to determine the refractive index and height of objects in three media based on the principle of light refraction. The method used was an experimental method. The results showed the refractive index values of the three media were quite accurate when compared to the absolute refractive index. The relationship of the angle of the incident ray was directly proportional to the angle of the refractive ray. The angle of light produced will be greater if the value of the given beam angle was greater. Thus, the set of refractive index laboratory tools developed is said to be good and suitable to be implemented in schools to explain the concept of the refractive index of light.