Simulation of reflectivity spectrum for non-absorbing multilayer optical thin films (original) (raw)
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Simulation of reflectivity spectrum
2009
Reflectivity simulation is an essential tool for the design and optimization of optical thin films. We have developed a reflectivity simulator for non-absorbing dielectric multilayer optical thin films using LabVIEW. The name of the substrate material as well as the material and thickness of each layer of the multilayer stack are fed into the program as input parameters in a pop-up window. The program calculates reflectivity spectrum for the given range of wavelengths using layer thicknesses and dispersion data of refractive indices for the defined stack of dielectric materials. The simulated reflectivity spectra for various combinations of materials in multilayer stacks are presented and compared with the experimental results of the multilayer optical thin films grown by electron-beam evaporation technique.
We have optimized and automated the experimental in-situ reflectivity measurement system for the laser diode (LD) facet coating. We have also developed a reflectivitysimulator program that gives the reflectivity data as a function of the thickness of the film (single or multi-layer) for a given wavelength, which aids in optimizing the above parameters while monitoring the coating of the films in-situ. We report the results for the in-situ reflectivity of a single layer MgF 2 and a quarter-wave optical thick three bi-layer pairs of MgF 2 and silicon on GaAs as a substrate for both the cases. We have achieved up to 83 % experimental reflectivity for the latter case.
Applied Optics, 2001
Using measurements of reflectance, transmittance, and the ellipsometric parameter ⌬, we have determined the thickness, refractive index, and the absorption coefficient of various thin films and thin-film stacks. ͑⌬, the relative phase between the p-and s-polarized components, is measured for both reflected and transmitted light.͒ These optical measurements are performed with a specially designed system at the fixed wavelength of ϭ 633 nm over the 10°-75°range of angles of incidence. The examined samples, prepared by means of sputtering on fused-silica substrates, consist of monolayers and trilayers of various materials of differing thickness and optical constants. These samples, which are representative of the media of rewritable phase-change optical disks, include a dielectric mixture of ZnS and SiO 2 , an amorphous film of the Ge 2 Sb 2.3 Te 5 alloy, and an aluminum chromium alloy film. To avoid complications arising from reflection and transmission losses at the air-substrate interface, the samples are immersed in an index-matching fluid that eliminates the contributions of the substrate to reflected and transmitted light. A computer program estimates the unknown parameters of the film͑s͒ by matching the experimental data to theoretically calculated values. Although our system can be used for measurements over a broad range of wavelengths, we describe only the results obtained at ϭ 633 nm.
Nano Express, 2021
A user-friendly software PRISA has been developed to determine optical constants (refractive index and extinction co-efficient), dispersion parameters (oscillator energy and dispersion energy), absorption co-efficient, band gap and thickness of semiconductor and dielectric thin films from measured transmission spectrum, only. The thickness, refractive index, and extinction co-efficient of the films have been derived using Envelope method proposed by Swanepoel. The absorption co-efficient in the strong absorption region is calculated using the method proposed by Connel and Lewis. Subsequently, both direct and indirect bandgap of the films is estimated from the absorption co-efficient spectrum using Tauc plot. The software codes are written in Python and the graphical user interface is programmed with tkinter package of Python. It provides convenient input and output of the measured and derived data. The software has a feature to cross check the results by retrieving transmission spec...
Applied Optics, 2006
A method for determining the optical constants and the thickness of weakly absorbing thin films on substrates is proposed. In this method only the reflectance and transmittance spectra obtained at a single arbitrary angle of incidence are used, provided that the former reveals several interference extrema. The calculation procedure is based on relatively simple relations suitable for the programmed realization and does not call for the prescription of the initial values of the parameters to be determined. The method proposed is fairly accurate and allows one to uniquely solve the inverse problem of spectrophotometry. The optical constants and the thickness of an As x Se y film formed on a glass substrate have been determined by the proposed method in the visible region of the spectrum.
Optical peculiarities of thin absorbing films
OPTIKA '98: 5th Congress on Modern Optics, 1998
Optical parameters of thin semiconductor films in visible region are investigated with two different methods: use the new analogues of Fresnel's formulas for absorbing media for calculation of reflection and transmission [1] and, use the calculation of an index of refraction on a base of a phase change on reflection. Results of these methods agree well. Thickness dependencies of n(d) and k(d) of Ge,Si,Se, Te were obtained for the experimental data [2]. Curves n(d) have resonance maxima at thicknesses, which are less than light wavelength in a medium in it times. Curves
Applied Optics, 2001
In this contribution a new efficient modification of a method that enables us to perform the optical characterization of nonabsorbing and weakly absorbing thin films without using the absolute values of the reflectances measured is presented. Namely, this modification is based on determining the values of the wavelengths corresponding to touching the spectral dependences of the reflectances of the studied films measured for several angles of incidence with the envelopes of maxima and minima of these spectral dependences. By means of combining the explicit formulas containing the wavelengths mentioned and the suitable iteration procedure one can evaluate the values of the thicknesses and spectral dependences of the refractive indices of the films analyzed in reliable and precise ways.