Bruggeman Effective Medium Research Articles

Measurement of the Optical Constants of Sand Samples Using Ellipsometry on Sand-Adhesive Composites.

In order to model the propagation of light through a sand cloud, it is critical to have accurate data for the optical constants of the sand particles that comprise it. The same holds true for modeling propagation through particles of any type suspended in a medium. Few methods exist, however, to measure these quantities with high accuracy. In this paper, a characterization method based on spectroscopic ellipsometry (SE) that can be applied to a particulate material is presented. In this method, a polished disc of an adhesive compound is prepared, and its optical constants are measured. Next, a mixture of the adhesive and a sand sample is prepared and processed into a polished disc, and SE is performed. By treating the mixture as a Bruggeman effective medium, the optical constants of the particulate material are extracted. For verification of the proposed method, it is first applied to pure silica powder, demonstrating good agreement between measured optical constants and literature values. It is then applied to Arizona road dust, a standard reference material, as well as real desert sand samples. The resulting optical constant data is input into a rigorous scattering model to predict extinction coefficients for various types of sand. Modeling results are compared to spectroscopic measurements on static sand samples, demonstrating good agreement between predicted and measured spectral properties including the presence of a Christiansen feature near a wavelength of 8 µm.

Electrical conductivity of geopolymer-graphite composites: Percolation, mesostructure and analytical modeling

The incorporation of carbon fillers into geopolymers enhances conductivity, forming intricate networks for integrated energy conversion in construction materials. This study employs a novel computational modeling approach to investigate the electrical conductivity of geopolymer-graphite composites. Utilizing a particle-based Monte Carlo method, percolation thresholds in virtual composite mesostructures are simulated, and Bruggeman's effective medium model is applied to predict conductivity. The research explores how mesostructural characteristics, including pore and particle size distribution, influence percolation and conductivity in multi-phase mixtures. The findings indicate that graphite polydispersity increases the percolation threshold from 10 vol% to 24.4 vol%, while the introduction of two additional (segregated) phases, metakaolin and pores, decreases the percolation threshold to 11.9 vol%. The concept of effective volume fraction is introduced to assess the influence of metakaolin and porosity on the percolation threshold. This enabled to establish a linear relationship between the electrical conductivity and effective volume fraction of graphite with a slope of 2 S/m/vol%. In a three-phase mixture, the percolation threshold is 12.18 vol%, with a 2.35% increase due to capillary water drying, enhancing graphite particle aggregation in the dried pores. Finally, Bruggeman's analytical effective medium model is used to simulate conductivity variation with increasing graphite content, aligning well with conductivity measurements. These findings provide valuable insights into percolation behavior and offer a relatively simple quantitative modeling approach to understand the factors influencing the effective conductivity of geopolymer-graphite composites.

A general objective-orientated automatic optimization of multi-layer thermochromic smart glazes

VO2-based thermochromic smart glazes have attracted much attention for energy-saving buildings. Their practical applications need high visible luminous transmittance (Tlum) and high solar light modulation efficiency (ΔTsol). High Tlum and ΔTsol are difficult to be realized by a single-layer VO2 film, and constructing multi-layer film assemblies has been a widely adopted way to increase Tlum and ΔTsol. Tlum and ΔTsol of a multi-layer film assembly are multi-dimensional functions of the complex dielectric permittivity and the thickness of each layer, respectively. The current research reported a computer automatic searching of the total minimum of an evaluation function that together takes the cool-state Tlum, hot-state Tlum, and ΔTsol into account. It can be used to optimize a multi-layer assembly composed of any components according to the given objectives and weights for Tlum and ΔTsol. Different multi-layer film systems consisting of SiO2, TiO2, and VO2 layers were optimized. The best film system was proposed to be TiO2/VO2/TiO2/s, and the effects of objectives and weights on Tlum and ΔTsol were also checked. The physical reason that leads to high Tlum and ΔTsol was analyzed based on the optimized reflectance and transmittance spectra. The RGB tristimulus of the optimized multi-layer system can also be obtained from the transmittance spectra. The program can also realize an automatic optimization with some variables being constrained, and the composite layers are also involved under the basis of the Bruggeman effective media theory. The results showed that a satisfied objective-orientated optimization can be realized for a thermochromic layer system; this should be meaningful for the design and preparation of the multi-layer film assemblies according to the different user's demands.

A doped-polymer based porous silicon photonic crystal sensor for the detection of gamma-ray radiation.

In this research, a theoretical investigation of the one-dimensional defective photonic crystals is considered for the detection of gamma-ray radiation. Each unit cell of the considered one-dimensional photonic crystals (1D PhCs) is composed of two layers designed from porous silicon infiltrated by poly-vinyl alcohol polymer doped with crystal violet (CV) and carbol fuchsine (CF) dyes (doped-polymer) with different porosity. In addition, a single layer of doped-polymer is included in the middle of the designed 1D PhCs to stimulate the localization of a distinct resonant wavelength through the photonic band gap. In particular, the appearance of this resonant mode represents the backbone of our study towards the detection of γ-ray radiation with doses from 0 to 70 Gy. The Bruggeman's effective medium equation, the fitted experimental data to the refractive index of the doped-polymer, and the Transfers Matrix Method (TMM) serve as the mainstay of our theoretical treatment. The numerical findings provide significant contributions to some of the governing parameters such as the thicknesses of the considered materials on the performance of the presented sensor, the effect of incidence angle and the porosity of the considered materials on the resonance wavelength. In this regard, at optimum values of these parameters the sensitivity, quality factor, signal-to-noise ratio, detection limit, sensor resolution, and figure of merit that are obtained are 205.7906 nm RIU-1, 9380.483, 49.315, 2.05 × 10-5 RIU, 3.27 × 10-5, and 2429.31 RIU-1, respectively. Therefore, we believe that the suggested design could be of significant interest in many industrial, medical, and scientific applications.

One-dimentional periodic structure infiltrated by (PVA/CV + CF)-polymer for high-performance sensitivity

In the current work, we demonstrate a design to act as a Gamma-ray radiation dosimeter based on the one-dimensional photonic crystal (1D-PhC). The basic concept of the present dosimeter is based on a Porous Silicon (PSi) infiltrated by poly-vinyl alcohol (PVA)-polymer doped with crystal violet (CV) and carbol-fuchsine (CF) dyes. The mechanism of suggested dosimeter is based on the shift of the photonic bandgap (PBG) to higher wavelengths as exposed to gamma-ray radiation doses from 0 to 70 Gray (Gy). The basic axes of the current theoretical treatment are the transfers matrix method (TMM), Bruggeman's effective medium equation, and the fitted experimental data to the refractive index of the doped PVA-Polymer. The obtained results showed the proposed sensor is characterized by high stable sensitivity varied from (178–186 nm/ RIU) along an applied γ-dose from (10–70 Gy) in the visible range. In addition, we compared these results with previous researches. In addition, based on the our knowledge may be it is the first time that a 1D-PhC has been used for gamma-ray detection by using (PVA/CV + CF) based on Porous Silicon.

Film thickness dependency and refractive index sensing capabilities of lossy mode resonances in metallic indium-rich ITO thin films

Film thickness plays a crucial role in determining the position and depth of lossy mode resonance (LMR). Herein, we explore the overall film thickness dependency of LMR properties of pulsed-laser-deposited metallic indium-rich indium tin oxide (ITO) thin films by employing a simple Kretschmann–Raether geometry. It is observed that the depth of LMR is increased monotonically with increasing film thickness. Extremely high attenuation values of − 20 d B for transverse electric and − 10 d B for transverse magnetic polarizations are achieved for the film with the greatest film thickness. Also, the LMR positions are considerably redshifted with increasing thickness. A numerical simulation algorithm based on the modified transfer matrix method, where surface roughness is taken into account with the application of anisotropic Bruggemann effective medium approximation, is used to simulate the experimental LMR spectra for all vacuum-deposited ITO thin films effectively. As an application of this study, refractive index (RI) sensing is demonstrated in the RI range of 1.3325–1.4459, and highest sensitivity values of 3840 nm/RIU and 2542 nm/RIU are accomplished for transverse electric and transverse magnetic polarizations, respectively. This study will help in attaining a deep level of understanding of the film thickness effect on thin film based LMR and elevate metallic indium-rich ITO as an excellent material template for LMR studies.

Segregated carbon nanotube networks in CNT-polymer nanocomposites for higher electrical conductivity and dielectric permittivity, and lower percolation threshold

In an effort to find higher electrical properties of CNT-based polymer composites, a segregated CNT (carbon nanotube) network model is constructed, and a computational scheme is also provided. The construction involves randomly oriented CNTs decorated on the surface of polymer particles. A two-scale computational scheme with segregated CNT networks as the small scale and the overall composite consisting of polymer particles and segregated networks as the large scale is proposed. The small-scale problem involves percolation feature and is solved through Bruggeman's effective-medium approximation, while the large-scale problem is solved with Hashin's exact approach in conjunction with the small-scale solution. The formulations are further extended to the complex domain for the analysis of frequency dependence under AC loading. In this process, the influence of interphase, electron tunneling, Maxwell-Wagner-Sillars polarization, Dyre's electron hopping, and Debye's dielectric relaxation, are also incorporated. The calculated results are validated with experimental data of 2-phase CNT/PA (polyamide) and 3-phase CNT/PA/PP (polypropylene) nanocomposites. Compared with homogeneously dispersed CNT systems, it is also demonstrated that segregated CNT networks can indeed lead to markedly higher conductivity and permittivity, and lower percolation threshold.

Hybrid Perovskite Degradation from an Optical Perspective: A Spectroscopic Ellipsometry Study from the Deep Ultraviolet to the Middle Infrared

AbstractA quantitative analysis of the thermally induced degradation of various device‐relevant multi‐cation hybrid perovskite films is performed using spectroscopic ellipsometry, for temperatures between 80 and 120 °C. The studied compositions are a triple cation perovskite Cs0.05(MA0.17FA0.83)0.95Pb(Br0.17I0.83)3, a Rb‐containing variant Rb0.05Cs0.05(MA0.17FA0.83)0.90Pb(Br0.17I0.83)3, and a methylammonium‐free Rb0.05Cs0.10FA0.85PbI3 composition. A very wide combined spectral range of 200 nm to 25 μm is covered by combining the data from two separate instruments. The relative changes in organic cation concentrations are quantified from the middle infrared molecular absorption bands, leveraging the use of point‐by‐point fitting for increased sensitivity. Additionally, the formation of PbI2 and non‐perovskite δ‐CsPbI3 phases is evidenced from Bruggemann effective medium fits to the visible and ultraviolet complex refractive indices. Methylammonium is almost completely depleted from the relevant compositions within 100 to 285 min of thermal annealing. The MA‐free perovskite degrades faster at intermediate temperatures, which is attributed to phase instability due to the formation of δ‐CsPbI3 in addition to PbI2.

Evolution of epsilon-near-zero plasmon with surface roughness and demonstration of perfect absorption in randomly rough indium tin oxide thin films

Any degree of surface roughness could play a significant role in determining the optical properties of ultra-thin films required for epsilon-near-zero (ENZ) applications. In this report, we have provided a systematic analysis of the evolution of an ENZ mode with increasing surface roughness values and established both experimentally and theoretically that roughness acts as a supporting mechanism for achieving a strong ENZ plasmon resonance response in randomly rough indium tin oxide thin films. For pulsed laser deposited indium tin oxide thin films, ENZ plasmon-mediated absorption is enhanced monotonically with the increasing surface roughness. A value of 99.75%, depicting near-perfect absorption, at a wavelength of 1335 nm for the incidence angle of 50° is demonstrated experimentally via Kretschmann–Raether configuration for the film with the highest surface roughness. A modified transfer matrix method based on the anisotropic Bruggemann effective medium approximation is being used to effectively simulate the experimental spectra, and based on this analysis, an even higher absorption is predicted at lower angles outside the experimentally viable domain. Such a high value of absorption just above the ENZ wavelength is due to the strong electric field enhancement inside the film layer, while in terms of absorption loss, surface roughness leads the way and contributes immensely toward the occurrence of perfect absorption in the collective media. Modification of the ENZ mode dispersion in the presence of a surface roughness layer is also discussed, and observed perfect absorption is recognized as the outcome of the crossover between the internal damping and radiation damping terms.

Reflection color tuning of a metal–insulator–metal cavity structure using arc plasma deposition of gold nanoparticles

Structural colors have diverse applications in optical filters, surface decoration, photovoltaics, and digital displays. In this study, an arc plasma deposition (APD) method was employed for fabrication of the top Au layer in the asymmetric Fabry–Perot cavity structure of Au/Si3N4/Al. With an increasing number of APD pulses (nP), the morphology of the Au layer gradually changed from a dispersion of nanoparticles (NPs) to a nanoporous film and then to a dense film, which in turn led to a change in the refractive index of the Au layer. The structural colors of the Au/Si3N4/Al structure were mainly governed by the interference effect. The optical constants of the NP-dispersed and nanoporous Au layers could be reasonably estimated based on Bruggeman's effective medium approximation. When the Au layers deposited with different nP were combined with dielectric Si3N4 layers of various thicknesses (hd), the full range of color hue with a wide range of color chroma could be realized using the Au/Si3N4/Al trilayer structure. The color hue was predominantly governed by hd, and the color chroma gradually increased with nP for a given value of hd.

Effective medium approximation based interpretation for Mueller matrix spectra of polydimethylsiloxane gratings

Dielectric corrugated gratings are of considerable interest due to their applications in acousto-optics, quantum electronics, integrated optics, spectroscopy, and holography integrated optics. Rigorous coupled-wave analysis has been widely used for the analysis of dielectric gratings. However, this approach is not only time-consuming and computer intensive but it also does not really promote the physical understanding of the origin of the observed optical behavior. Here, we use Mueller matrix (MM) spectroscopic ellipsometry to systematically study the sinusoidal polydimethylsiloxane grating. We correlate the observed polarization mixing in the Mueller matrix to the underlying physical origin using the physics-based approach. The calculated MM contour plots obtained from a biaxial Bruggemann effective medium approximation model are completed by the presence of Rayleigh-Woods anomalies. The roles of optical interference, geometric anisotropy, and diffraction orders are respectively identified by their different dispersion behavior, with their interactions and couplings highlighted. Such a straightforward procedure provides a new method for analyzing dielectric gratings, which requires considerably less computer power and is directly linked to the physical interpretations.

1D porous silicon photonic crystals comprising Tamm/Fano resonance as high performing optical sensors

We theoretically discuss a new design for the sensing and detection of chemical and biomedical fluids based on the change in their indices of refraction in the refractive index range 1−1.5. The transfer matrix method in cylindrical coordinates and the Bruggeman's effective medium approximation represent the theoretical overview of our study. The metallic cap in front of a ternary porous silicon photonic crystal induces Tamm / Fano states inside the photonic band gap that take part of the resonant peaks in conventional defected PCs. Analysis shows that the spectral positions of these states are very sensitive to changes in refractive index of the void fluids. In particular, the proposed sensor could provide higher performance than many previous 1D photonic crystals sensors. At a void refractive index of 1.1, our design exhibits a sensitivity of 6770 nm/RIU and a quality factor of 662. Therefore, the detection and sensing procedures of chemical and biomedical fluids could be investigated in a rather much efficient, stable and novel technique that has not been applied before.

Characterization of optically effective complex refractive index of black carbon composite aerosols

Black carbon aerosols, always existing as complicated mixtures of various species, have important impacts on the global and regional climate, whereas their effective aerosol complex refractive index (ACRI) is a must for modeling their radiative effects. Retrieval of optically effective ACRI from accurately calculated scattering and absorption properties of an internal-mixed aerosol model with BC and dust coated with sulfate, roughly representing ambient aged multicomponent BC particles, are performed. The sensitivities of retrieved optically effective ACRI to particle size distribution and composition ratio are explored, and the popular volume weighted average (VWA) method and Bruggeman effective medium (BEM) theory are also considered for comparison. The optically effective ACRIs depicts dramatic variation for monodisperse size parameter larger than π, as opposed to almost a constant for size parameter less than π, whereas the VWA and BEM can hardly provide acceptable effective ACRIs for coarse BC composite particles. The retrieved optically effective ACRI are sensitive to both size distribution and composition ratio, and becomes more sensitive to particle size distribution with aerosols containing more BC content. As BC volume content reaches ~4%, the VWA overestimates the imaginary part of effective ACRI with significant bias when compared with the optically effective ACRI, indicating overestimated aerosol absorption in most atmospheric environments in aerosol-climate models employing the VWA. We suggest that the optically effective ACRI, rather than the ACRI given by the VWA, should be applied to account for coarse BC-containing particles in the state-of-the-art aerosol-climate models.

Thermal hysteresis measurement of the VO2 dielectric function for its metal-insulator transition by visible-IR ellipsometry

The real and imaginary parts of the dielectric function of VO2 thin films, deposited on r-plane sapphire via pulsed laser deposition, are measured by means of visible-infrared ellipsometry for wavelengths ranging from 0.4 to 15 μm and temperatures within its phase transition. For both the insulator-to-metal (heating) and metal-to-insulator (cooling) transitions, it is shown that the two ellipsometric signals exhibit three temperature-driven behaviors, which are well described by appropriate combinations of the Tauc-Lorentz, Gaussian, and Drude oscillator models. By fitting Bruggeman's effective medium model for the dielectric function to the corresponding measured experimental values, using the volumetric fraction of the VO2 metallic domains as a fitting parameter for different temperatures within the VO2 phase transition, we have found that this model is suitable for describing the dielectric function in visible and near-infrared wavelengths (∼0.4 to ∼3.0 μm), but it generally fails for longer infrared ones. Furthermore, the hysteresis loop of the VO2 emissivity averaged over a relevant interval of wavelengths is determined and shown to vary from ∼0.49, in the insulator phase, to ∼0.16, in the metallic one. These values, based on the VO2 dielectric function, are consistent with previous measurements reported in the literature, and therefore, our measured data are expected to be useful for describing the behavior of VO2 films involved in optical and radiative applications.

High-contrast infrared polymer photonic crystals fabricated by direct laser writing.

One-dimensional (1D) photonic crystals (PCs) were fabricated by three-dimensional (3D) direct laser writing using a single polymer to obtain reflectance values approaching that of a gold reference in the near-infrared (near-IR) spectral range. The PCs are composed of alternating compact and low-density polymer layers that provide the necessary periodic variation of the refractive index. The low-density polymer layers are composed of subwavelength-sized pillars which simultaneously serve as a scaffold while also providing refractive index contrast to the adjacent compact polymer layers. The Bruggemann effective medium theory and stratified-layer optical-model calculated reflectivity profiles were employed to optimize the PC's design to operate at a desired wavelength of 1.55μm. After the fabrication, the PC's structure was compared to the nominal geometry using complementary scanning electron microscopy and optical microscopy micrographs identifying a true-to-form fabrication. The performance of the PCs was investigated experimentally using FTIR reflection and transmission measurements. A good agreement between stratified-layer optical-model calculated and measured data is observed. Therefore, we demonstrate the ease of predictive design and fabrication of highly efficient 1D PCs for the IR spectral range using 3D direct laser writing of a single polymer.

Dielectric Insights into the Microcosmic Behavior of Ionic Liquid-Based Self-Assembly—Microemulsions/Micelles

Dielectric relaxation spectra of ([Bmim][BF4]/TX-100/ p-xylene) microemulsions and ([Bmim][BF4]/TX-100) micelles were measured. A specific dielectric relaxation changing with the concentration of ionic liquids (ILs) was observed in the range of 106-108 Hz. When dielectric parameters were combined with the Einstein displacement equation and Bruggeman's effective-medium approximation, the interaction between [Bmim][BF4] and p-(1,1,3,3-tetramethylbutyl) phenoxypolyoxyethyleneglycol (TX-100) in microemulsions/micelles was presented: because of the electrostatic interaction and van der Waals force, [Bmim][BF4] is bound around the polyethylene oxide (PEO) chains of TX-100, and once the electric field is added, ions of [Bmim][BF4] will move along the PEO chain. The dependence of dielectric and phase parameters such as relaxation time, permittivity, and volume fraction on the mass fraction of ILs presents an evidence for our proposals about the transition of both systems with the increase of IL content. In addition, it was confirmed that percolation is a unique phenomenon in microemulsions and the percolation mechanism here belongs to static percolation. The transition process of micelles with the change of IL content is presented from the dielectric view.

Enhanced microwave electromagnetic properties of core/shell/shell-structured Ni/SiO2/polyaniline hexagonal nanoflake composites with preferred magnetization and polarization orientations

Core/shell/shell-structured Ni/SiO2/polyaniline hexagonal nanoflakes possessing in-plane [111] easy magnetization (M) and out-of-plane interfacial polarization (P) are synthesized by a three-step liquid chemical method, and their physicochemical properties and growth mechanism are investigated. Three characteristic types of paraffin-bonded ring-shaped nanoflake composites having random (R), vertical–horizontal (V–H), and horizontal–vertical (H–V) orientations of the orthogonal M and P to their two major surfaces are prepared by randomly, vertically, and horizontally aligning the nanoflakes in the paraffin matrix under a magnetic alignment and thermal curing process. The composites are evaluated experimentally and theoretically in the L–Ku (1–18 GHz) bands of microwaves in order to investigate the orientation effect of the orthogonal M and P on their microwave electromagnetic properties. The in-plane M in the H–V-oriented composite and the out-of-plane P in the V–H-oriented composite, which are parallel to the effective magnetic and electric field vectors of incident microwaves, result in a significant enhancement in permeability with multiple magnetic natural resonances and an obvious improvement in permittivity in comparison with other composites, respectively. The observations agree with the theoretical predictions based on the Landau–Lifshitz–Gilbert equation and Bruggeman's effective medium theory for permeability and the Debye's polarization theory for permittivity. As a result, the H–V-oriented composite achieves the best microwave electromagnetic impedance matching and absorption with a broad absorbing bandwidth of 4 GHz, a wide thickness range of 7–10 mm, and a minimal reflection loss of −41.5 dB in the Ku (12–18 GHz) band.

Broadband near-infrared antireflection coatings fabricated by three-dimensional direct laser writing.

Three-dimensional direct laser writing via two-photon polymerization is used to fabricate anti-reflective structured surfaces (ARSSs) composed of subwavelength conicoid features optimized to operate over a wide bandwidth in the near-infrared range from 3700 cm-1 to 6600 cm-1 (2.7-1.52μm). Analytic Bruggemann effective medium calculations are used to predict nominal geometric parameters such as the fill factor of the constitutive conicoid features of the anti-reflective structured surfaces (ARSSs) presented here. The performance of the ARSSs was investigated experimentally using infrared reflection and transmission measurements. An enhancement of the transmittance by 1.35%-2.14% over a broadband spectral range from 3700 cm-1 to 6600 cm-1 (2.7-1.52μm) was achieved. We further report on finite-element-based reflection and transmission data using three-dimensional (3D) model geometries for comparison. A good agreement between experimental results and the finite-element-based numerical analysis is observed once as-fabricated deviations from the nominal conicoid forms are included in the model. 3D direct laser writing is demonstrated here as an efficient method for the fabrication and optimization of ARSSs designed for the infrared spectral range.

Study of the optical properties of silver nanoparticle layers and Si‐based nanostructure layers

Ellipsometric spectra (λ = 250–900 nm) of surface layers were for the first time obtained in three stages of the catalytic etching of silicon, used to fabricate wire‐like nanostructures. Self‐assembled silver particles deposited with chemical method on the silicon surface form a discontinuous layer with its own complex dielectric function ϵ, which is independent of the radiation incidence angle (at 50–70 degrees relative to the normal to the surface) and differs from ϵ of the bulk silver structure. The variation of the imaginary part of the pseudodielectric function, ϵ2, of the layer of silicon nanowire (SiNW) sprouts was studied. At the minimum catalytic etching duration, the thickness of the rough SiNW layer being formed is comparable with the thickness of the layer of preliminarily deposited silver. With increasing etching duration, a low‐refractive SiNW layer is formed with a thickness of 111 nm and void fraction of 33–78%, found in Bruggeman's effective medium approximation. The experimental data obtained with a spectroscopic ellipsometry and their interpretation made it possible to determine specific features of nanostructures at the earliest interval silicon etching time.

Safe and simple detection of sparse hydrogen by Pd-Au alloy/air based 1D photonic crystal sensor

A simple integrated hydrogen sensor using Pd-Au alloy/air based one dimensional photonic crystal with an air defect layer is theoretically modeled. Structural parameters of the photonic crystal are delicately scaled to generate photonic band gap frequencies in a visible spectral regime. An optimized defect thickness permits a localized defect mode operating at a frequency within the photonic band gap region. Hydrogen absorption causes modification in the band gap characteristics due to variation of refractive index and lattice parameters of the alloy. As a result, the transmission peak appeared due to the resonant defect state gets shifted. This peak shifting is utilized to detect sparse amount of hydrogen present in the surrounding environment. A theoretical framework is built to calculate the refractive index profile of hydrogen loaded alloy using density functional theory and Bruggeman's effective medium approximation. The calculated refractive index variation of Pd3Au alloy film due to hydrogen loading is verified experimentally by measuring the reflectance characteristics. Lattice expansion properties of the alloy are studied through X-ray diffraction analyses. The proposed structure shows about 3 nm red shift of the transmission peak for a rise of 1% atomic hydrogen concentration in the alloy.