基于柔性纳米压印工艺制备中红外双层金属纳米光栅

摘要

用纳米压印工艺制备红外金属光栅时,硬模板压印极易造成光栅结构缺陷致使光栅性能下降.本文采用柔性纳米压印工艺作为替代方法制备了适合在3-5 μm波段工作,高度为100 nm,上下金属层厚为40 nm的双层金属纳米光栅,其光栅结构参数为:周期200 nm,线宽100 nm,深宽比1∶1.该方法采用热纳米压印工艺将母模板光栅结构复制到IPS(Intermediate Ploymer Sheet)材料上,制作出压印所需软模板;随后通过紫外纳米压印工艺将IPS软模板压印到STU-7压印胶,得到结构完整均匀的介质光栅;最后在介质光栅上垂直热蒸镀金属铝,完成中红外双层金属纳米光栅的制备.对所制备光栅进行了测试,结果表明,所制备光栅在2.5～5 μm波段的TM偏振透射率超过70％,在2.7～5 μm波段的消光比超过30 dB,在2.72～3.93 μm波段的消光比超过35 dB,显示了优异的消光比特性和偏振特性.该研究结果在红外偏振探测、红外偏振传感等方面具有潜在应用.%In nanoimprint lithography of infrared metallic gratings,the grating structure is easily damaged by hard template nanoimprint lithography and their polarization characteristics would be reduced.This paper proposes a flexible nanoimprint lithography as the alternative method to fabricate the bilayer metallic nano grating with a height of 100 nm and a thickness of 40 nm.The grating is suitable for working at 3-5μm and its main parameters are the period in 200 nm,line width in 100 nm,and the aspect ratio in 1 ∶ 1.In fabrication,the master template grating structure was copied to the Intermediate PloymerSheet (IPS) material by thermal nanoimprint lithography to obtain IPS soft template for the embossing.Then,the IPS grating structure was transferred to the STU-7 resist by UV-embossing lithography to get the dielectric grating with complete and uniform structure.Finally,Al was deposited on this grating by vertical thermal evaporation,and the mid-infrared bilayer metallic nano grating was successfully fabricated.The fabricated grating was tested.The results show that the transverse magnetic transmittance of this mid-infrared bilayer metallic nano grating is greater than 70％ in the 2.5-5 μm,and its extinction ratio is more than 30 dB in the 2.7-5μm,especially it is greater than 35 dB in the 2.72-3.93 μm,showing excellent extinction ratio and polarization characteristics.These results demonstrate that the grating fabricated here has potential applications in infrared polarization detection and infrared polarization sensing.