title: Transmittance enhancement of sapphires with antireflective subwavelength grating patterned UV polymer surface structures by soft lithography.
abstract: We report the total and diffuse transmission enhancement of sapphires with the ultraviolet curable SU8 polymer surface structures consisting of conical subwavelength gratings (SWGs) at one- and both-side surfaces for different periods. The SWGs patterns on the silicon templates were transferred into the SU8 polymer film surface on sapphires by a simple and cost-effective soft lithography technique. For the fabricated samples, the surface morphologies, wetting behaviors, and optical characteristics were investigated. For theoretical optical analysis, a rigorous coupled-wave analysis method was used. At a period of 350 nm, the sample with SWGs on SU8 film/sapphire exhibited a hydrophobic surface and higher total transmittance compared to the bare sapphire over a wide wavelength of 450-1000 nm. As the period of SWGs was increased, the low total transmittance region of < 85% was shifted towards the longer wavelengths and became broader while the diffuse transmittance was increased (i.e., larger haze ratio). For the samples with SWGs at both-side surfaces, the total and diffuse transmittance spectra were further enhanced compared to the samples with SWGs at one-side surface. The theoretical optical calculation results showed a similar trend to the experimentally measured data.
authors: Soo Hyun
authors: SH
authors: Lee
authors: Jung Woo
authors: JW
authors: Leem
authors: Jae Su
authors: JS
authors: Yu
mesh_terms: D000327:Adsorption / Q000528:radiation effects; D000537:Aluminum Oxide / Q000737:chemistry* / Q000528:radiation effects; D004852:Epoxy Compounds / Q000737:chemistry*; D008422:Materials Testing; D054802:Molecular Imprinting / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry* / Q000528:radiation effects; D010781:Photography / Q000379:methods*; D011108:Polymers / Q000737:chemistry*; D012031:Refractometry / Q000379:methods*; D013499:Surface Properties / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D004852:Epoxy Compounds; D011108:Polymers; C520895:SU-8 compound; D000537:Aluminum Oxide