Metal-Dielectric mirrors utilizing three gradient refractive index dielectric materials for 10.6 μm wavelength applications

Abstract

Thin films are crucial in optics, particularly in fabricating high-reflectivity mirrors for high-power lasers. We propose a novel approach that transcends traditional low–high refractive index (LH) structures by designing a metal-dielectric mirror composed of three materials with gradient refractive indices. The optimal process was selected by thoroughly investigating the properties of ZnSe and YbF₃ thin films under varying ion-assisted energies. Using Macleod software, we meticulously designed the optical thicknesses of the ZnSe and YbF₃ coatings, striking a delicate balance between reflection and absorption within the mirror’s dielectric layer, thereby minimizing the overall reflection loss. The resulting mirrors exhibited a remarkable reflectivity of 99.92 % at a wavelength of 10.6 μm, coupled with a significantly low stress level of −18.66 MPa. These results boost the efficiency and durability of laser systems, underscoring the potential of mirrors for various industrial applications.