The enhanced light diffuse reflection of laser marking Al substrate for the back reflector purpose

This study set out with the aim of assessing the possibilities of incorporating the laser marking strategies for the purpose of diffuse back reflector fabrication. The correlation between the laser process parameters of fabricated samples' microstructure and their optical properties has been determined. The laser texturizing was conducted on the aluminum substrate throughout the Nd:YAG (1064 nm) laser varying the laser process parameters, i.e. scanning speed (v) and pulse repetition rate (f). The effect of laser irradiation on surface nanostructure was investigated by means of confocal optical microscopy (COM) and scanning electron microscopy (SEM). In order to evaluate the phase composition and optical properties of fabricated nanotextures, the X-ray diffraction (XRD) and spectrophotometric measurements were performed. The obtained reflectance spectra of samples were used to perform the colorimetry analysis and calculate the luminous reflectance. The morphological evaluation of patterned surfaces gives evidence of periodic crater-shaped structures formation influenced by chaotic radial-ligaments patterns resulting from splashing liquid metal solidification. Laser-textured Al reflectors show almost similar total reflectance as the untreated substrate whereas the significant enhancement of diffuse reflectance of patterned sample series can be observed. The different hues of white colour appear on all laser-patterned Al surfaces. The calculated luminous reflectance of proceeded samples ranging from 65% to 75%. The overall results show the effectiveness of the laser marking process in order to obtain highly diffusive scattering layers on Al substrate without employing any additional coating.