Comparative Study for Designing Two Optical Multilayers Stacks ThF4/AlF3 and ThF4/LiF

Abstract

The dielectric materials ThF4, AlF3 and LiF and with refract index n=1.5143 n=1.36 and n=1.393 respectively had been used for the optical design Glass/L/H/Air and for two cases Glass/AlF3/ThF4/Air and Glass/LiF/ThF4/Air for 30 layers and for design wavelength λₒ=550 nm and quarterwave thicknesses. The results of this comparative study explain the peak of the gaussian curves. It will increase with increasing the layers but this increase is higher for Glass/AlF3/ThF4/Air and the width of the curves will decrease with increasing the number of layers for the two cases, this will fix the color of the coating and reflect narrow band in the visible region. All results exhibit the coating with AlF3/ThF4 is the best and more efficient for coloration and thermal gain than LiF/ThF4 coating. This study is considered as a modern idea by comparing two multi-layer optical designs and exhibiting which one is better than the other in terms of the solar transmittance (τsol.), solar reflectance (ρsol.), visible reflectance (ρvis.) and coloring efficiency (M), and employ it in the field of building elements for façade solar collectors cladding.

Keywords

• multi-layers stick
• thin films
• facades collectors
• colored glazing.