Large-area broadband ultralow reflectance biomimetic structures silicon via femtosecond laser inducing and chemical etching

The low efficiency of femtosecond laser processing and the ordinary antireflection performance are still huge obstacles that dramatically inhibit the practical application of femtosecond laser antireflection technology. Inspired from the moth eye, this paper aims to propose a novel and highly efficient method to fabricate the broadband ultralow reflectance biomimetic structures silicon via femtosecond laser inducing and chemical etching. Different from the traditional micro size focus spot of femtosecond laser, a beam shaping strategy is used to generate centimeter scale line beam to fabricate hierarchical structures on silicon surface, which dramatically increases the manufacturing efficiency. Then, based on the structural differences induced by line beam, a screen block strategy and a chemical etching method are involved to selectively fabricate antireflective biomimetic micro pillars in a large area. Accordingly, the reflectance of biomimetic structures is lower than 0.2 % in the wavelength of 300 nm–2500 nm, and the omnidirectional reflectance is lower than 0.6 % and 1.4 % for S polarization and P polarization light at different incident angles (20°–80°), respectively. Additionally, it only takes <35 min to fabricate biomimetic structures of 24.8 × 24.8 mm² on Si surface with such outstanding antireflection performance, which is highly efficient.