超快激光制备金属表面微纳米抗反射结构进展

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

材料表面抗反射性能在太阳能利用、光电子产品、红外传感和成像、军事隐身、以及航空航天等领域均具有重要应用价值。文中对材料表面抗反射特性的重要用途、人工实现路径、表面抗反射结构的研究现状及存在的问题等做了详细的论述。目前，国内外学者已经利用碳纳米管涂层和硅表面针状纳米结构实现了优异的超宽波谱抗反射性能。但迄今为止，金属表面微纳米结构的抗反射能力仍有很大的改善空间。作者所在的清华大学材料学院激光加工研究团队运用新一代高功率高频率超快激光，在金属表面制备出多种类型的特征微纳米结构，对其抗反射性能进行系统研究，实现了紫外一可见、紫外一近红外、紫外一中红外与紫外一远红外分别为2％、6％、5％和8％的超宽光谱超低反射率，并且在0～60°入射角度范围内无明显变化。进一步在微纳米结构基础上发展了“宏一微纳一纳米线”多级多尺度复合结构，在16—17μm波长处的总反射率低至0．6％，在14—18μm波长处总反射率不超过3％。上述优异超宽光谱抗反射性能预期具有良好应用前景。

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 ultrabroad-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 16-17μm and keeping steadily below 3% over a broad band of 14-18μm. The outstanding ultra-broad-band spectrum antireflection properties are anticipated to have good prospects in various applications in future.