Progress on ultrafast laser fabricating metal surface micro-nano antireflection structures

Surface antireflection properties are of great value in many fields including solar utilization, optoelectronic products, infrared sensing/imaging, stealth, aerospace technologies, etc. Here, the applications, the artificial realization routines of surface antireflection properties were summarized, as well as the state of the art in the surface antireflection structures. Currently, scientists have achieved ultra-broad-band antireflection performances through carbon nanotube coatings and silicon nanotip array structures. However, there is still much room for the improvement of the antireflection properties of metal surface micro/nano structures. Based on the next generation high power high repetition rate ultrafast laser system, the Laser Materials Processing Research Grouop in Tsinghua University has successfully fabricated diverse metal surface micro-nano structures and conducted systematic research on their antireflection properties. The average reflectance of metal surfaces in the UV-VIS, UV-NIR, UV-MIR, and UV-FIR regions are reduced down to around 2%, 6%, 5%, and 8%, respectively, exhibiting ultra-broad-band highly effective antireflection properties. Besides, these antireflection performances show little change within the incident angle range of 0-60. Further, macro-micronano-nanowire hierarchical structures are also developed, reaching an ultralow total reflectance of 0.6% at the infrared wavelength around 16-17 m and keeping steadily below 3% over a broad band of 14-18 m. The outstanding ultra-broad-band spectrum antireflection properties are anticipated to have good prospects in various applications in future.