红绿共振互补光变亚波长微结构制作与分析

Fabrication and Analysis of Red-Green Resonant Complementary Optically Variable Sub-Wavelength Microstructures

剖析了双层亚波长光栅微结构的设计及制作原理,提出了一种亚波长微结构设计与制作的新方法,其特点是以矩形亚波长光栅设计微结构,用全息干涉光刻及涂布的方法制作,却不影响设计微结构的共振及光变特性,还能改善反射光的颜色质量。用该方法设计及制作了具有"红绿"共振互补光变效果的亚波长防伪微结构,检验了其共振光变光谱与颜色变化特征。研究表明:制作的全息光栅微结构的共振及光变特征如共振光谱、颜色、光谱峰及峰分裂等与预先设计的相同;矩形亚波长光栅并不是共振的必要条件,其他面形光栅微结构的衍射特性和等效波导若与矩形光栅微结构的相同,则其相关特性相同;用新方法设计及制作亚波长光变微结构的工艺是可行的,既降低了设计微结构的加工难度,又便于用现有的全息生产设备批量生产。

Principles of design and production of dual-layer sub-wavelength grating microstructures are analyzed thoroughly. Novel methods for designing and fabricating such structures, with the characteristics of using rectangular grating index profiles when designed and using holographic interference lithography and coating processes when produced, are proposed. Microstructures fabricated by use of this method, will have the same resonant and optically variable properties with pre-designed structures, even improving its color qualities of lights reflected. A sub-wavelength security microstructure with the unique performances of red-green resonant complementary optically variability in color was designed and manufactured successfully and its resonant optically variable spectrum and color changing characteristics were verified theoretically and experimentally. Study results indicate that sinusoidal grating microstructures manufactured have the same resonant and optically variable characteristics, such as the resonant spectrum, color, spectral peak and peak splits, etc. with the pre-designed structures. A rectangular index profile grating is not the necessary requirement to produce resonance behaviors and the grating regions can have any profile such as the holographic type as long as its diffraction characteristics and equivalent waveguide representation are the same with the designed rectangular grating microstructures. The methods proposed are feasible in practice, lowering the making complexity and with potential of low-cost mass production commercially by use of the current holographic manufacture equipments.