Inverse Synthesis Method Research Articles

Correlation of optical parameters of pure and doped Ge17Sb8Se75-xErx chalcogenides films using transmission spectra

Six compositions of erbium (Er) doped Ge17Sb8Se75-xErx(x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) chalcogenide bulk have been synthesized by melt quenching technique. Further, systematic studies of chemical composition based optical parameters via Inverse synthesis methods have been carried out. Thin films of these chalcogenides have been deposited using thermal evaporation technique (∼10−4 Pa) on the microscopic glass substrate which are found to be amorphous. Transmission spectroscopy carried out in the range 400–2000 nm has been used as the signature of these compositions to calculate various optical parameters. Further, inverse synthesis method is used to estimate the refractive index (n), extinction coefficient (k), and thickness (d) of thin film. In the strong absorption region, absorption coefficient is calculated with the help of method suggested by Connel and Lewis. The systematic compositional dependency on Er doped has been established with refractive index and band gap of chalcogenide glasses. The refractive index dispersion is also discussed in terms of the single oscillator using the Wemple-Di Domenico model. The chemical composition dependent parameters such as dispersion energy, oscillator energy have been calculated to understand the order parameter.

An Inverse Procedural Modeling Pipeline for SVBRDF Maps

Procedural modeling is now the de facto standard of material modeling in industry. Procedural models can be edited and are easily extended, unlike pixel-based representations of captured materials. In this article, we present a semi-automatic pipeline for general material proceduralization. Given Spatially Varying Bidirectional Reflectance Distribution Functions (SVBRDFs) represented as sets of pixel maps, our pipeline decomposes them into a tree of sub-materials whose spatial distributions are encoded by their associated mask maps. This semi-automatic decomposition of material maps progresses hierarchically, driven by our new spectrum-aware material matting and instance-based decomposition methods. Each decomposed sub-material is proceduralized by a novel multi-layer noise model to capture local variations at different scales. Spatial distributions of these sub-materials are modeled either by a by-example inverse synthesis method recovering Point Process Texture Basis Functions (PPTBF) [ 30 ] or via random sampling. To reconstruct procedural material maps, we propose a differentiable rendering-based optimization that recomposes all generated procedures together to maximize the similarity between our procedural models and the input material pixel maps. We evaluate our pipeline on a variety of synthetic and real materials. We demonstrate our method’s capacity to process a wide range of material types, eliminating the need for artist designed material graphs required in previous work [ 38 , 53 ]. As fully procedural models, our results expand to arbitrary resolution and enable high-level user control of appearance.

Effect of laser irradiation on optical properties of Ge12Sb25Se63 amorphous chalcogenide thin films

The change in photo-induced optical properties in thermally evaporated Ge12Sb25Se63 chalcogenide thin film under 532-nm laser illumination has been reported in this paper. The structure and composition of the film have been examined by X-ray diffraction and energy dispersive X-ray analysis, respectively. The optical properties such as refractive index, extinction coefficient and thickness of the films have been determined from the transmission spectra based on inverse synthesis method and the optical band gap has been derived from optical absorption spectra using the Tauc plot. It has been found that the mechanism of the optical absorption is due to allowed indirect transition. The optical band gap increases by 0.05 eV causing photo-bleaching mechanism, while refractive index decreases because of reduction in structural disordering. Deconvolution of Raman and X-ray photoelectron spectra into several peaks provides different structural units, which supports the optical photo-bleaching.

Photo-induced optical bleaching in Ge12Sb25S63 amorphous chalcogenide thin films: effect of 532 nm laser illumination

The photo-induced effects of Ge12Sb25S63 films illuminated with 532 nm laser light are investigated from transmission spectra measured by FTIR spectroscopy. The material exhibits photo-bleaching (PB) when exposed to band gap light for a prolonged time in a vacuum. The PB is ascribed to structural changes inside the film as well as surface photo-oxidation. The amorphous nature of thin films was detected by x-ray diffraction. The chemical composition of the deposited thin films was examined by energy dispersive x-ray analysis (EDAX). The refractive indices of the films were obtained from the transmission spectra based on an inverse synthesis method and the optical band gaps were derived from optical absorption spectra using the Tauc plot. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple–DiDomenico model. It was found that the mechanism of the optical absorption follows the rule of the allowed non-direct transition. Raman and x-ray photoelectron spectra (XPS) were measured and decomposed into several peaks that correspond to the different structural units which support the optical changes.

Investigation of elastic and optical properties of electron beam evaporated ZrO2–MgO composite thin films

Thin films of composite materials are being progressively explored for achieving tunability in the optical constants for application in multilayer optical devices. In the present study, a set of ZrO2–MgO binary mixed composite thin films have been prepared by reactive electron beam evaporation of solid solution of ZrO2 and MgO at different oxygen partial pressures. Since elastic properties of the thin films are very important for their environmental stability under high power laser application, elastic moduli (indentation moduli) of the films have been measured by atomic force acoustic microscopy measurements. The optical properties especially refractive index of such films has been determined from the optical transmission measurement using an inverse synthesis method, while the density of such films has been measured by grazing incidence X-ray reflectivity. The variation of the elastic moduli of the thin films as a function of oxygen partial pressure used during deposition has been studied and the above variation has been corroborated with the variation of density and refractive index of the thin films.

Optical properties and microstructure of Ta_2O_5 biaxial film

This study investigates the optical properties and microstructure of Ta(2)O(5) film deposited with the glancing angle deposition technique. The tilted nanocolumn microstructure, examined with scanning electron microscopy, induces the optical anisotropy of thin film. The optical properties of thin film are characterized with an inverse synthesis method. Based on the Cauchy model, the dispersion equations of optical constants of film are determined from the transmittance spectra measured at normal and oblique incidence over 400-800 nm. The starting values derived with an envelope method quicken the optimization process greatly. The dispersion of the principal indices N(1), N(2), and N(3) and the thickness d of thin film are presented statistically. A good agreement between the measured optical properties and theoretical calculation is obtained, which validates the model established for thin film produced by glancing angle deposition.

Structural Dynamics Optimization Based on a Hybrid Inverse Synthesis Method Using a Quadratic Approximation

This paper lies within the framework of the so-called redesign problem of structures subjected to dynamic constraints. A hybrid synthesis algorithm is developed, combining the truncated modal basis of the initial system and the spatial or material co-ordinates of an added component, which is modelled with shell-type finite elements parameterized with respect to a shape factor. Based upon a quadratic inverse formulation, the proposed technique shows several advantages in comparison to other synthesis methods, such as a refined sensitivity strategy, a powerful modal synthesis approach and a simplified optimization phase. Numerical examples are provided illustrating the capabilities of the novel procedure.

Spectrophotometric analysis of aluminum nitride thin films

The optical functions of AlN thin films deposited on the quartz substrates by the reactive radio frequency magnetron sputtering, such as refractive index, extinction coefficient, optical band gap, and film thickness were determined from the transmittance and reflectance spectra in the range of 190–820 nm. For these analyses, an inverse synthesis method was established after literature survey. The results were doublechecked with a modified envelope method, and compared with those of previous reports. Spectroscopic ellipsometry analyses were performed to confirm the accuracy of the methods. Refractive indices of AlN films in this study were in the range of 1.95–2.05 at 633 nm and 2.26–2.38 at 250 nm, depending on the preparation conditions. The extinction coefficients were small (<5×10−4) and nearly constant at low energy region (<2 eV), but exhibited various dispersion features at 2.2–3.5 eV, indicating different amount and kinds of defects of AlN films. The absorption coefficient at near-band-gap energy exhibited a strong thickness dependence, resulting in various optical band-gap energies ranging 5.34–5.71 eV.

Use of the inverse synthesis method for the determination of the optical constants of paper in the far infrared

Optical thin film methods were used to determine the refractive index and absorption coefficient of paper at 70.5,96.5, and 118.8 μm. Transmittances and reflectances were measured of paper, two quartz and two TPX plates, as well as of the paper pressed between the quartz and TPX plates. Measurements were performed at angles of incidence between 0 and 50°. The optical constants found provided a reasonable fit between the experimental points and the calculated performance. The small residual departures between the two sets of data are probably due to inhomogeneities within the paper.