Study On Fabrication Of Large Area Sub-wavelength Anti-reflection Film By Soft-nanoimprinting

Research on improving surface antireflection based on sub-wavelengthstructures is a hot topic. It is very significant to restrain Fresnel reflection ofmany photoelectric devices. The optical action of sub-wavelengthantireflection structures is creating a graded refractive index layers whichleads to a major substantial reduction of the reflectance of the photoelectricdevices surface. A soft lithographic approach using a modified polyurethaneacrylate (PUA) mold for the fabrication of sub-wavelength antireflectivestructure on polymer film is reported. By introducing an intermediatetransferring PUA mold generated by an anodized aluminum oxide membrane,there is no need either to heat nor to deposit metal as a seed layer. Therefore,the most costly and time-consuming master preparation step in theconventional process chain is not a necessity. The soft PUA mold provides ahigh resolution of100nm with an aspect ratio of1.7and a conformal contactwith the substrate and reduces the pressure needed during the imprintingsteps. It is numerically verified that the antireflective film with nanoporeshas a similar fascinating broadband antireflective effect compared with thatof its complementary nanonipple one. In our experiment, the average transmission efficiency of the PET film with dual-side nanopores can beenhanced to98.7%at normal incidence and92.5%at an incident angle of60°over a range of400~800nm of the spectrum. The proposed method is simpleand cost-effective and the fabricated antireflective polymer film can bemounted on the surfaces of various optical devices for the reduction ofFresnel reflections.