Refractive Index Dispersion Research Articles

Variation of structure and optical material dispersion in lead borate glass containing multi valence chromium and germanium cations

In pursuit of manufacturing glass having a high refractive index and low dispersion, a series of lead and borate glasses containing germanium and chromium oxide by composition 25B2O3-73.8PbO-xGeO2-(1.2 − x)Cr2O3, with 0 ≤ x ≤ 1.2 mol.%, are prepared. IR measurements are carried out to explore the structure of as-prepared samples. The deconvoluted IR peaks revealed presence of bridging oxygen up to x = 0.6 mol%. At x > 0.6 mol% none bridging oxygen is the dominant. The dependence of the measured hydrostatic density and corresponding molar volume for the studied compositions are analyzed and discussed. The dispersion curves of refractive index (n) and absorption index (k) are calculated in the spectral range 300–2500 nm. The effect of increasing the ratio GeO2/[GeO2 + Cr2O3] on the calculated dispersion energy, lattice energy, oscillator energy and material dispersion are deduced. For photonic applications, the wavelength at zero material dispersion for the investigated samples is calculated and compared with other systems based on Borates, silicates and Germinate fiber. The results recommend that the present glass could be used in different modern optoelectronics devices.

Optical and microstructural characterization of nanocrystalline Cu doped ZnO diluted magnetic semiconductor thin film for optoelectronic applications

A series of Zn 1-x Cu x O nanocrystalline films were deposited on a silica substrate using e-beam evaporation technology. The physical properties of the deposited film were closely examined using x-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), atomic force microscopy (AFM), and spectroscopic ellipsometry (SE). The deposited film's structure revealed the formation of a hexagonal wurtzite structure, with no extra phases found. According to AFM analysis, the deposited Zn 1-x Cu x O (x = 0.0, 0.04, 0.08, 0.12, 0.16, and 0.2) film has nanocrystalline characteristics. The present findings show that increasing Cu content up to x ≤ 0.2 reduces the direct optical energy gap E g from 3.286 eV (x = 0) to 2.934 eV (x = 0.2), which can be attributed to the sp-d exchange coupling. The refractive index dispersion extracted from SE analysis for Cu-doped ZnO thin films increased as the Cu dopant increased. In addition, the refractive index dispersion of the deposited film was studied using a single oscillator model proposed by Wemple-DiDomenico (WDD). It was found that the oscillator energy E o decreases as the Cu concentration increases, while the dispersion energy E d increases. As a result of the improvement in the optical energy band gap and the tunability of the values of the dispersive oscillator parameters E o , E d , n 0 , ε 0 , M -1 , and M -3 with increasing Cu doping levels, Cu doped ZnO films are a good candidate for optoelectronic device applications. • E-beam techniques is used to deposit a series of thin film of Cu doped ZnO. • The deposited film's structure show the formation of a hexagonal wurtzite structure. • SE technique is used to obtained the direct energy gap and found that E g is reduced from 3.286eV to 2.934eV with Cu concentration increases from 0 up to 0.2. • The SE analysis reveal that refractive index dispersion of Cu-doped ZnO thin films has increased as the Cu dopant has increased.

Optical constants of the as-prepared and annealed (Se80Te20)94Ag6/PMMA thin films

Thin films of (Se80Te20)94Ag6/PMMA have been deposited on glass substrate by thermal co-evaporation technique. Melt quenching approach has been adopted to prepared bulk (Se80Te20)94Ag6 chalcogenide glass. Glass transition temperature of bulk (Se80Te20)94Ag6 glass and poly (methyl methacrylate) (PMMA) polymer have been found out by differential scanning calorimetry (DSC) at a heating rate of 10 K/min. Thin films were annealed above glass transition temperatures of glass (332 K) and polymer (340 K) at two different temperatures 343 K and 365 K. The presence of different phases in annealed film was confirmed by X-ray diffraction studies. Transmission spectra of as-deposited and annealed films were obtained by Uv-Vis spectroscopy in the wavelength range of 350-900 nm. To analyze refractive index dispersion Wemple-Didomenico model have been used. Optical parameters viz refractive index (n), extinction coefficient (k), real and imaginary dielectric constants (ε′ and ε′′) and optical band gap (Eg) are calculated by using optical transmittance. The increasing behavior of the optical band gap with increase in annealing temperature is explained on the basis of density of state model.

Dispersion of Complex Refractive Indices for Intense Vibrational Bands. II. Implication to Sum Frequency Generation Spectroscopy.

Sharp and intense vibrational bands are characterized with conspicuous dispersion of complex refractive indices. Based on the quantitative data of dispersion in the preceding paper, this paper clarifies the influence of the dispersion on the sum frequency generation (SFG) spectroscopy. As a consequence of the large dispersion, the lineshapes of SFG spectra could be influenced by the frequency dependence of the Fresnel factor as well as the nonlinear susceptibility. This paper argues the relative importance of the two factors in general cases and provides a useful criterion to evaluate their importance. The effect of Fresnel dispersion becomes significant when the SFG spectrum involves a sharp and intense vibrational band as well as a large non-resonant background susceptibility, typically in some solid-liquid interfaces. A possible way to correct the effect of Fresnel dispersion is suggested using the heterodyne measurement.

Dispersion of Complex Refractive Indices for Intense Vibrational Bands. I. Quantitative Spectra.

This paper reviews the dispersion of complex refractive indices for representative intense vibrational bands of organic liquids in the absolute scale. Conspicuous variations in both real and imaginary refractive indices over the intense bands are precisely determined as a function of infrared wavenumber by attenuated total reflection infrared absorption measurement. The accurate spectral data offer an excellent reference to calibrate the absolute infrared intensities by various quantum chemical calculations, and thus, critical comparison between the present experiment and computation was reported to clarify the general accuracy of the quantum chemical calculations. The precise data of the dispersion will be utilized to clarify their impact on the analysis of vibrational spectroscopy of interfaces in the subsequent paper.

Microstructured single-mode IR fibers based on metal halides with increased mode-field diameter

This paper presents the results of a study of the refractive-index dispersion for the AgBr–TlI, AgBr–TiBr0.46I0.54, and AgCl–AgBr crystal systems in the spectral range from 0.4 to 56 µm, along with the results of the development and fabrication of single-mode microstructured IR fibers by extrusion from solid solutions of metal halides. The fibers had a central insert 16 µm in diameter of composition 2.6 mol% TlI in AgBr, located in a matrix of composition 2.3 mol% TlI in AgBr with external diameter 525 µm. Inserts with diameter 16 µm of composition 2.0 mol% TlI in AgB were placed in the matrix in hexagonal order. The distribution of the radiation emitted from the fibers in the far field at wavelength 10.6 µm was studied, along with the influence of local heating of a section of the fiber on the transport of the IR radiation. The mode-field diameter was experimentally estimated as 120±30µm. The fibers were suitable for transporting both laser and thermal radiation from heated objects to a thermal viewer.

Fabrication of Cellulose-Based Biopolymer Optical Fibers and Their Theoretical Attenuation Limit.

Currently, almost all polymer optical materials are derived from fossil resources with known consequences for the environment. In this work, a processing route to obtain cellulose-based biopolymer optical fibers is presented. For this purpose, the optical properties such as the transmission and the refractive index dispersion of regenerated cellulose, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate were determined from planar films. Cellulose fibers were produced using a simple wet-spinning setup. They were examined pure and also coated with the cellulose derivatives to obtain core-cladding-structured optical fibers. The cellulose-based optical fibers exhibit minimum attenuations between 56 and 82 dB m-1 at around 860 nm. The ultimate transmission loss limit of the cellulose-based optical fibers was simulated to characterize the attenuation progression. By reducing extrinsic losses, cellulose-based biopolymer optical fibers could attain theoretical attenuation minima of 84.6 × 10-3 dB m-1 (507 nm), 320 × 10-3 dB m-1 (674 nm), and 745.2 × 10-3 dB m-1 (837 nm) and might substitute fossil-based polymer optical fibers in the future.

Magnetic plasmons induced in a dielectric-metal heterostructure by optical magnetism

Abstract We investigate numerically and experimentally the optical properties of the transverse electric (TE) waves supported by a dielectric-metal heterostructure. They are considered as the counterparts of the surface plasmon polaritons (i.e., the transverse magnetic (TM) waves) which have been extensively studied in the last several decades. We show that TE waves with resonant wavelengths in the visible light spectrum can be excited in a dielectric-metal heterostructure when the optical thickness of the dielectric layer exceeds a critical value. We reveal that the electric and magnetic field distributions for the TE waves are spatially separated, leading to higher quality factors or narrow linewidths as compared with the TM waves. We calculate the thickness, refractive index and incidence angle dispersion relations for the TE waves supported by a dielectric-metal heterostructure. In experiments, we observe optical resonances with linewidths as narrow as ∼10 nm in the reflection or scattering spectra of the TE waves excited in a Si3N4/Ag heterostructure. Finally, we demonstrate the applications of the lowest-order TE wave excited in a Si3N4/Ag heterostructure in optical display with good chromaticity and optical sensing with high sensitivity.

Stationary optical solitons with cubic–quartic law of refractive index and nonlinear chromatic dispersion

This paper recovers stationary optical solitons for the newly established cubic–quartic form of nonlinear refractive index together with nonlinear chromatic dispersion. The study is extended to the generalized form of cubic–quartic nonlinearity and later with generalized temporal evolution. The extended Jacobi's elliptic function expansion is implemented in all cases to recover the stationary solitons.

Enhancement of multifunctional optoelectronic and spintronic applications of nanostructured Cr-doped SnO2 thin films by conducting microstructural, optical, and magnetic measurements

A chemical synthesis method was used to produce Cr-doped SnO2 nanoparticles. By using the TEM technique, the nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) nanopowder was confirmed. With different Cr concentrations, the electron beam deposition technique was used to deposit a series of Sn1-xCrxO2 nanocrystalline thin films on a silica substrate. X-ray diffraction (XRD), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and vibrating sample magnetometry (VSM) techniques were used to examine the physical properties of the deposited films. The nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) thin film was confirmed by XRD and AFM morphology measurements. The XRD spectrum of the Sn1-xCrxO2 nanocrystalline film demonstrated a tetragonal crystal structure with no detectable extra phases. The optical measurements showed that as the Cr content increases, the direct optical energy gap Eg decreases without any sign of solubility limit up to x ≤ 0.1. The decrease in Eg is attributed to the sp-d exchange interaction. Also, the spectral behavior of the refractive index dispersion of the Cr-doped SnO2 indicates that as the Cr dopant increases, the refractive index of the deposited film also increases, which is attributed to the increase in the polarizability. Moreover, as the Cr content raises the atomic number, the density of the deposited film increases from 1.43 × 1022 cm−3 for SnO2 to 1.57 × 1022 cm−3 for Sn0·9Cr0·1O2. Further, the behavior of the refractive index dispersion of the deposited film was revealed using a single oscillator model proposed by Wemple-DiDomenico (WDD). Our calculations revealed that as the Cr concentration increases, the value of oscillator energy Eo decreases owing to the decrease in Eg, whereas the value of dispersion energy Ed increases because of the chemical structural changes such as the lattice parameters. Finally, the magnetic studies revealed that incorporating a small fraction of Cr into SnO2 produces room temperature ferromagnetism in the film, which is gradually suppressed by a further increase in Cr doping. These findings indicate that the Cr-doped SnO2 film can be recommended for optoelectronic and spintronic device applications.

Studies structure, surface morphology, linear and nonlinear optical properties of nanocrystalline thin films of manganese (III) phthalocyanine chloride for photodetectors application

Manganese (III) Phthalocyanine Chloride (MnClPc) thin films were deposited over glass substrates through the thermal evaporation technique. The structural characteristics of MnClPc films at various thicknesses have been studied using X-ray diffraction (XRD), which revealed an amorphous structure. The atomic force microscope (AFM) investigates the surface morphology of MnClPc thin films and demonstrates that films have nanostructure with a size of 58 nm for thickness 55 nm and slightly increased with increasing film thickness. Spectrophotometer analyses of MnClPc thin films obtained over the wavelength range of 300−2500 nm were used to determine the linear and nonlinear optical parameters. Results indicate that the optical energy gap of MnClPc films was slightly changed due to thickness. The parameters of the optical dispersion were considered using a single-oscillator model. Also, the nonlinear refractive index and susceptibility were determined by the concepts of linear refractive index dispersion. The optical limiting characteristics by using two different types of laser showed a considerable reduction in the laser output power by increasing the film thickness. This intensive result for MnClPc will probably implement in an industrial approach in the field of photodetectors and optoelectronic devices.

Group velocity of light in biaxial crystals.

Based on the wave vector surface, we have derived the analytical expressions for the group velocity of light traveling in an optically biaxial crystal in an arbitrary direction. Our formulas are in terms of either the wave vector direction or the ray direction. An axis dispersion vector is introduced to specify the rotation of the dielectric frame in monoclinic and triclinic crystals, which is found to be responsible for the asymmetry of the group velocity surfaces of these two crystal systems when compared to their phase and ray velocity surfaces. Our formulas confirm that the group velocity of light in a nondissipative medium equals the ratio between the Poynting vector and the total energy density of the electromagnetic field. The group index of light is found to be decomposable into three parts: the ray index, the group index due to principal refractive index dispersion, and that due to axis dispersion. Numerical calculations are performed for the group velocity of light in ${\rm Sn}_2{\rm P}_2{\rm S}_6$ crystal at 550 nm wavelength. Our results show that the dispersion of the principal refractive indices has a considerable contribution to the group index.

The dependence of medium refractive index on optical properties of gold nanorods and their SERS application

In this article, the influence of the medium refractive index on optical properties of gold nanorods (GNRs) and their surface enhanced Raman spectroscopy application were studied. In particular, GNRs have been applied in biomedical sensors to detect diseases by monitoring the changes in the environment. In this study, the changes in optical properties of GNRs were investigated according to the medium refractive index changes in the cationic surfactant cetyltrimethylammonium bromide (CTAB) during synthesis processes as well as GNR dispersion in different medium refractive indices. For instance, in the solutions with different concentrations of CTAB, GNRs were coated by biomolecules [such as PEG, bovine serum albumin (BSA), and glutathione (GSH)], which have different refractive indices. The fundamental reason for the change in optical properties of GNRs is also elucidated. GNRs have been used to enhance surface Raman scattering to detect indigo molecules. The results showed that due to the surface plasmon resonance effect, the GNRs could strongly enhance the scattering signal of indigo dyes, with the lowest detectable concentration of up to 10−8 M and with an enhancement coefficient of over 2000 times.

Investigation of optical non-linearity of lead-free ferroelectric potassium sodium niobate (K0.35Na0.65NbO3) thin films via two-wave mixing phenomenon

In the present work, structural, morphological and optical properties of lead- free ferroelectric Potassium Sodium Niobate (K0.35Na0.65NbO3 or KNN) films (~1 µm thin), grown using pulsed laser deposition (PLD) technique at distinct substrate temperature, have been studied. The bandgap and the refractive index value of KNN thin films at different substrate temperatures (700–800 °C) are found to be in the range of 3.6–4.0 eV and 2.14–2.37 respectively. The refractive index dispersion of KNN films has been fitted using Wemple- DiDomenico’s single oscillator model. Two-wave mixing phenomenon has been exploited via pump-probe technique to investigate the non-linear optical property of KNN thin films having gold microdisks at the surface. The periodic transmission pattern of probe intensity evidently signifies the non-linear optical behaviour of the KNN thin films. The enhancement in the probe beam intensity when the pump beam is kept unblocked indicates the exchange of energy between the pump and probe beams. The non-linear optical response in KNN film is also attributed to the orientation of ferroelectric domains in the direction of the net electric field, along with the occurrence of surface plasmon (SP) modes resulting in the stronger coupling of the pump and probe beams.

Optical properties of novel oxyfluoride glasses on the systems of LaF3–LaO3/2–NbO5/2 and LaF3–LaO3/2–NbO5/2–AlO3/2

AbstractOxyfluoride glasses of xLaF3–(60 − x)LaO3/2–40NbO5/2 (x = 0, 5, 10, 35) and xLaF3–(60 − x)LaO3/2–30NbO5/2–10AlO3/2 (x = 0, 10, 20, 30) were prepared using a levitation technique. Both the glass‐transition temperature, Tg, and onset crystallization temperature, Tc, were lowered by substituting a part of the oxygen with fluorine in the glasses. An appropriate amount of fluorine maximized the difference between the temperatures, ΔT (= Tc − Tg), indicating the improvement in the glass‐forming ability. The atomic packing densities of the glasses were approximately 60%, which gradually increased with the fluorine content. The absorption edge of the glasses shifted toward the shorter wavelength region in the ultraviolet spectra and toward the longer region in the infrared spectra by fluorine substitution. In addition, in one of the oxyfluoride glasses, a wide transparency from 307 nm to 9.2 µm was realized. Furthermore, the glass exhibited superior optical properties, with a combination of a high refractive index, nd, of 2.020 and low wavelength dispersion, vd, of 30.1. The effect of fluorine substitution on the nd and its vd was analyzed using the Lorentz–Lorenz dispersion formula.

Argon pressure dependent optoelectronic characteristics of amorphous tin oxide thin films obtained by non-reactive RF sputtering process

In this work, amorphous tin oxide thin films were deposited by non-reactive radio frequency magnetron sputtering. A ceramic $${\text{SnO}}_2$$ target was used, while different working pressures were employed. The target to substrate distance was fixed to 17 cm, and the substrate was not intentionally heated. The properties of $${\text{SnO}}_2$$ (thickness, refractive index dispersion, optical band gap, resistivity, free carriers concentration, carriers mobility, carriers majority type and their scattering time) have been inferred from spectroscopic ellipsometry, conventional UV-Vis spectroscopy and specific Hall electrical measurements. Thickness and refractive index are slightly dependent on the deposition conditions, while the optical band gap, free carriers concentration and their mobilities are changing from sample to sample. The evolution of the optical band gap and carriers concentration is correlated to the active defects concentration. Amorphous $${\text{SnO}}_2$$ films grown at 0.4 Pa have the lowest resistivity of $$0.86\,\Omega \, \hbox {cm}$$ , a carrier concentration of $$1.05 \times 10^{18}\,\hbox {cm}^{-3}$$ , and a Hall mobility of $$6.8\,\hbox {cm}^{2}$$ / Vs. The average optical transmittance in visible spectrum is 76%.

Theoretical and experimental behavior of optical properties of Er3+ doped fluoroaluminate glasses

The study of a new composition of fluoride glasses based on a mixed fluoroaluminate matrix with small additives of phosphates was carried out. Advanced thermal stability ΔT of the initial glassy matrix, exceeding the classical fluoride systems, was established from the difference between the glass transition temperatures and the onset of crystallization (ΔT = 108 °C). Refractive index dispersion was obtained based on the Sellmeier equations. The radiative characteristics of fluoroaluminate glass samples with different erbium contents were studied in order to evaluate the efficiency of luminescence in the visible and near IR regions. It was found that the theoretical and experimental values of the luminescence lifetimes of energy levels 2H11/2, 4S3/2, 4F9/2 and 4I13/2 depend on the concentration of erbium ions. The effect of concentration quenching of upconversion luminescence bands was found; for near infrared emission around 1.5 μm the quantum efficiency was 96 % in the absence of luminescence quenching.

Characteristics of Poly(vinyl Alcohol) (PVA) Based Composites Integrated with Green Synthesized Al3+-Metal Complex: Structural, Optical, and Localized Density of State Analysis.

The influence of dispersing Al-metal complex on the optical properties of PVA was investigated using UV–visible spectroscopy. Polymer composite films with various Al3+-complex amounts in the PVA matrix were arranged by solution casting technique by means of distilled water as a widespread solvent. The formation of Al3+-metal complex was verified through Ultraviolet–visible (UV-Vis) and Fourier-transform infrared spectroscopy (FTIR) examinations. The addition of Al-complex into the polymer matrix led to the recovery of the optical parameters such as dielectric constant (εr and εi) and refractive index (n). The variations of real and imaginary parts of complex dielectric constant as a function of photon wavelength were studied to calculate localized charge density values (N/m*), high-frequency dielectric constant, relaxation time, optical mobility, optical resistivity, and plasma angular frequency (ωp) of electrons. In proportion with Al3+-complex content, the N/m* values were amplified from 3.68 × 1055 kg−1 m−3 to 109 × 1055 kg−1 m−3. The study of optical parameters may find applications within optical instrument manufacturing. The optical band gap was determined from Tauc’s equation, and the type of electronic transition was specified. A remarkable drop in the optical band gap was observed. The dispersion of static refractive index (no) of the prepared composites was analyzed using the theoretical Wemple–DiDomenico single oscillator model. The average oscillator energy (Eo) and oscillator dispersion energy (Ed) parameters were estimated.

Optical properties of native (anodic) layer on the InAlAs surface of different morphology

The influence of InAlAs/InP(001) heterostructures surface morphology on the optical properties (dispersive refractive index and extinction coefficient) of the anodic layer, formed by the oxidation in low-energy Townsend gas-discharge O2-Ar-containing plasma at room temperature, was studied using atomic force microscopy and ellipsometry methods. High resolution transmission electron microscopy and X-ray photoelectron spectroscopy were used to determine the anodic layer morphology and chemical composition. It is shown that the growth structural defects (pits) on the InAlAs surface, with a density 106–107 cm−2, do not significantly influence the optical properties of the amorphous anodic layers, mainly consisting of In2O3, Al2O3, As2O3 and elemental arsenic quite uniformly distributed over their depth and area. The thickness of thin (≤10 nm) oxide layers on InAlAs is measured at a high accuracy by the nondestructive ellipsometry method using the optical model of a single-layer isotropic film on an absorbing substrate.

Determination of Dispersion Relation and Optical Parameters Induced by Exciton–Polariton Effect in Whispering-Gallery Microcavities Using Photoluminescence Spectroscopy

To realize the refractive index dispersion accurately is essential for the design of optical devices. In this paper, we study hexagonal ZnO microrod cavities. We measure angle-resolved photolumines...