Fabrication and Analysis of Red-Green Resonant Complementary Optically Variable Sub-Wavelength Microstructures
CHEN Yong-li1，LIU Wen-xia1，LIAO Ning-fang2
1. College of Packaging & Printing Engineering，Tianjin University of Science & Technology，Tianjin 300222，China 2. National Lab of Color Science and Engineering，School of Information Science and Technology﹐ Beijing Institute of Technology，Beijing 100081，China
Abstract：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.
Key words：Sub-wavelength microstructures;Holographic gratings;Fabrication and analysis;Resonant spectra and optical variability
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