[引用][C] Biomimetic surfaces for high‐performance optics

Y Li, J Zhang, S Zhu, H Dong, F Jia, Z Wang… - Advanced …, 2009 - Wiley Online Library
Y Li, J Zhang, S Zhu, H Dong, F Jia, Z Wang, Z Sun, L Zhang, Y Li, H Li, W Xu, B Yang
Advanced Materials, 2009Wiley Online Library
Periodic optical microstructures are abundant in biological systems, and have provided
enormous inspiration for scientists to mimic them for optical applications. Some nocturnal
insects use arrays of non-close-packed nipples of sub-300-nm size as antireflective
structures (ARS) to reduce reflection from their compound eyes.[1–5] The ARS on the
corneas of these insects can also increase light transmission in dark conditions, which
improves sensitivity of light vision. In practical applications, simultaneously suppressing …
Periodic optical microstructures are abundant in biological systems, and have provided enormous inspiration for scientists to mimic them for optical applications. Some nocturnal insects use arrays of non-close-packed nipples of sub-300-nm size as antireflective structures (ARS) to reduce reflection from their compound eyes.[1–5] The ARS on the corneas of these insects can also increase light transmission in dark conditions, which improves sensitivity of light vision. In practical applications, simultaneously suppressing surface reflection and increasing transmission of light is crucial to the performance of an optical system, especially when there are several optical components involved. For flat-panel displays, antireflective surfaces are usually employed to increase transmission and eliminate ghost image or veil glare due to reflection from the optical surfaces.[6] Despite the technical importance, actual material solutions for improved performance are limited, especially in the ultraviolet spectral region.[7] To date, two kinds of approaches are available for fabricating antireflective surfaces. One is coating porous or multilayered films [6, 8–14] on the surface of devices. The other is fabricating subwavelength ARS (moth’s eye structures) directly on the surface of devices.[15–18] The ARS surfaces exhibit distinct advantages compared to coatings.[19] First, the ARS surfaces exhibit higher mechanical stability and better durability than coatings because no foreign materials are involved when they are used over a broad thermal range.[19] Second, the material of the ARS surfaces is the same as that of devices, while coating materials with appropriate refractive index are rare in nature. Last, the ARS surfaces have many tunable factors, such as the spacing, depth and cross-sectional geometry. Similar to the nipple arrays in insects’ compound eyes and wings,[1] the ARS surfaces with nipple-like or tapered profiles exhibit a gradient in refractive index between air and substrate. Therefore, they can dramatically suppress the reflection losses at the interface over a large range of wavelengths and a large field of view.[17] Many techniques based on top-down lithography, such as electron-beam etching,[20, 21] fast atom beam [22] and interference lithography [15] have been applied to fabricated ARS surfaces. To avoid scattering from the optical interface, the structure dimension at an optical interface has to be smaller than the wavelength of the incident light.[23] For ultraviolet and visible light applications, feature sizes below 200 nm are always necessary. In such small size ranges, conventional top-down lithographic technologies require sophisticated equipment, are timeconsuming and expensive to fabricate over the large areas required for practical applications. Moreover, processing of non-planar lenses, especially with a small curvature radius, is almost impossible due to the difficulty of fabricating masks on non-planar surfaces. Recently, ARS surfaces on silicon prepared by nanosphere lithography have been reported,[18, 24] but there are few ARS surfaces on fused silica or on non-planar lenses. Spatz and co-workers have prepared fused silica hollow pillar arrays;[25] such arrays exhibit high performance antireflective properties in the deep ultraviolet region, although the antireflective properties in the visible region is suboptimal due to the pillars having a smaller spacing than the wavelength of visible light. The nipple arrays on the compound eyes of insects exhibit both antireflective and self-cleaning properties.[26] Recently, multifunctional antireflective surfaces have attracted a lot of interest because the additional functions can improve the performance of optical …
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