Design and Fabrication of Dual-Scale Broadband Antireflective Structures on Metal Surfaces by Using Nanosecond and Femtosecond Lasers

摘要： Antire?ective surfaces, with their great potential applications, have attracted tremendous attention and have been the subject of extensive research in recent years. However, due to the signi?cant optical impedance mismatch between a metal surface and free space, it is still a challenging issue to realize ultralow re?ectance on a metal surface. To address this issue, we propose a two-step strategy for constructing antire?ective structures on a Ti-6Al-4V (TC4) surface using nanosecond and femtosecond pulsed lasers in combination. By controlling the parameters of the nanosecond laser, microgrooves are ?rst scratched on the TC4 surface to reduce the interface re?ection. Then, the femtosecond laser is focused onto the sample surface with orthogonal scanning to induce deep air holes and nanoscale structures, which e?ectively enhances the broadband absorption. The antire?ection mechanism of the dual-scale structures is discussed regarding morphological characterization and hemispherical re?ectance measurements. Finally, the modi?ed sample surface covered with micro-nano hybrid structures is characterized by an average re?ectance of 3.1% over the wavelengths ranging from 250 nm to 2250 nm.