Effect of Annealing Temperature on Metal/Dielectric Multilayers for Fabricating Broadband Pulse Compression Gratings

Metal/dielectric multilayers were prepared by physical vapor deposition process using gold as the metal material, HfO2 and SiO2 as high and low refractive index materials, respectively. These stacks were used to fabricate broadband pulse compression gratings. Influences of annealing temperature on the surface root-mean-square roughness, reflectivity and resistance to chemical cleaning damage were investigated. The experimental results indicated that surface root-mean-square roughness of these multilayers changed only slightly after annealing. Their resistance to chemical cleaning damage improved with the annealing temperature increase, whereas their reflectivity decreased. The metal/dielectric multilayers annealed at 250°C for 10 h could not only endure the process of chemical cleaning, but also slightly decrease the reflectivity, suggesting that it is an optimal annealing process for metal/dielectric multilayers.