Using Narrow Line-Width Laser to Measure the Thickness and Refractive Index of the Film

We demonstrate applications of a novel setup which is used for measuring the relative phase difference between S and P polarization at an oblique incidence point in optically denser medium by analyzing the relative frequency shift of adjacent axial modes of S and P resonances of a monolithic folded Fabry-Perot cavity (MFC). The relative phase difference at a reflection point A in an optically denser medium is inferred to be around -167.4° for a confocal cavity and -201.1° for a parallel cavity. Given the n1, n3, φ1, φ3, λ, and Δ, the elliptic formula tan(ψ)exp(iΔ) = Rp/Rs is used to find a solution for thickness d and refractive index n2 of the thin film coated on point A, where Rs and Rp are total refractive index of s and p component of light related to two unknown values. Since it is hard to deduce an analytical solution for thickness and refractive index of the film, we firstly used exhaustion method to find the set of solution about thickness and refractive index when assumed there is no light absorption by the film and then Particle Swarm Optimization (PSO) to find a set of solution of thickness and complex refractive index which accounts the light absorption by the film.

Design of Optical Filter Using Bald Eagle Search Optimization Algorithm

Controlled thermonuclear reactors require consistent monitoring of plasma in the toroidal chamber.Better working conditions of such machines can be monitored by analyzing its radiations.Various wavelengths such as 656.3,486.1,464.7 nm are quite significant which are used for health monitoring of thermonuclear machines.The optical thinfilmfilters which work on construc-tive and destructive interference are the ideal choices.Thesefilters are multi-layered with a pair of high and low refractive index dielectric materials.Significantly high transmission index at the desired wavelength and relatively low transmission at the other wavelengths are desired.With this as the objective,it is necessary to design thefilter.Various optimization techniques are used for identifying the suitable design of thefilters.To choose the parameter combination that provides the most excellent performance,optimization of the design para-meters is entailed.The goal of this work is to improve the optical bandfilter using the Bald eagle search optimization(BES)method.The ideal design is determined by assessing several characteristics such as thickness,refractive index,Full-Width at Half-Maximum(FWHM),and the impact of choosing optical properties,which increases transmission potential.Initially,an alternate multi-layer stack with 28,30,and 32 layers is created by altering the thickness while keeping the dielectric substances high and low refractive indices constant.By adjusting the thickness of each layer,the BES algorithm achieves the best practical solution.The proposed method is implemented using MATLAB and the outcomes show the efficacy of the proposed technique.The transmittance,reflectance,and FWHM using the pro-posed BES are found to be 99.9356%,0.065%,and 1.2 nm respectively.

Generating soil thickness maps by means of geomorphological-empirical approach and random forest algorithm in Wanzhou County,Three Gorges Reservoir

Soil thickness,intended as depth to bedrock,is a key input parameter for many environmental models.Nevertheless,it is often difficult to obtain a reliable spatially exhaustive soil thickness map in widearea applications,and existing prediction models have been extensively applied only to test sites with shallow soil depths.This study addresses this limitation by showing the results of an application to a section of Wanzhou County(Three Gorges Reservoir Area,China),where soil thickness varies from 0 to40 m.Two different approaches were used to derive soil thickness maps:a modified version of the geomorphologically indexed soil thickness(GIST)model,purposely customized to better account for the peculiar setting of the test site,and a regression performed with a machine learning algorithm,i.e.,the random forest,combined with the geomorphological parameters of GIST(GIST-RF).Additionally,the errors of the two models were quantified,and validation with geophysical data was carried out.The results showed that the GIST model could not fully contend with the high spatial variability of soil thickness in the study area:the mean absolute error was 10.68 m with the root-mean-square error(RMSE)of 12.61 m,and the frequency distribution residuals showed a tendency toward underestimation.In contrast,GIST-RF returned a better performance with the mean absolute error of 3.52 m and RMSE of 4.56 m.The derived soil thickness map could be considered a critical fundamental input parameter for further analyses.

Simultaneous quality improvement of the roughness and refractive index of SiC thin films

We deposite silicon carbide thin layers on cleaned Si（100） substrates using the plasma enhanced chemical vapor deposition method,and show that the RFTIR spectrum is periodic in the near and medium infrared ranges. It is shown that both the deposition rate and the uniformity of the thin films are decreased by increasing the substrate temperature,and that the refractive index is increased by increasing the substrate temperature.This shows that there is a trade-off between the quality improvement of the uniformity and refractive index.