Preparation and Performance Investigation of Broadband Antireflection Coatings in the Visible and Near-Infrared Spectral Regions

A seven-layer broadband antireflection coating consisting of Al2O3, TiO2, SiO2, and MgF2 was designed and deposited on both sides of K9 glass for the 400–1100 nm range. The deposition parameters for TiO2 and SiO2 single layers were optimized, and the measured optical constants were used in TFCalc to refine the multilayer design. Layer-specific thickness-tolerance analysis was performed to identify the layers requiring strict process control. The initially characterized double-sided coating showed an average transmittance of 98.72% over 400–1100 nm. Four samples prepared in one additional deposition batch exhibited closely matching transmittance spectra, indicating low sample-to-sample variation within that batch. Five-position profilometry indicated consistent total-thickness control. Cross-sectional scanning electron microscopy (SEM) revealed well-defined multilayer contrast without obvious cracking, and regional energy-dispersive X-ray spectroscopy (EDS) analysis detected the constituent elements of the coating. These results demonstrate a practical design-to-fabrication approach that combines process-specific optical constants with tolerance analysis, with potential applications in imaging systems, optical windows, and lidar.