Research On The Anti-counterfeiting Devices Based On Subwavelength Grating

Due to the progress of high-resolution digital scanning equipment and 3D printing technology, the safty level of traditional anti-counterfeiting security products is declining, and can not play a important role in anti-counterfeiting. All kinds counterfeit goods flood into the market leading to great harm to the interests of consumers, and loss of national economy.New technology is important to improve the capability of security products.This paper proposes a novel method of anti-counterfeiting based on sub-wavelength gratings.Sub-wavelength gratings and true-color images are experimentally fabricates based on the electron beam lithography, dry etching and nano-imprinting.Firstly, the basic principle of guided mode resonance and the method to realize optical variable image based on guided mode resonance are introduced.Then, the mechanism of guided mode resonance in subwavelength grating structure is analyzed. The influence of structure parameters on the resonance peak and spectral characteristics of gratings are studied using numerical simulations.Coupled wave equations are establised to simulate the diffraction efficiency of the subwavelength grating. A genetic algorithm is utilized to optimize subwavelength structure for higher efficiency and better spectrum purity.Finally, optical variable device based on sub-wavelength grating is fabricated using electron beam lithography, inductively coupled plasma etching and nano-imprinting process. The fabricated device are charactrized using probe and detection system uses.Optical filtering effect and true color image for anti-counterfeiting are realized.Anti-counterfeit devices base on the optical filtering effect due to the guided mode resonance in sub wavelength grating are designed and experimentally relized.The device consists of high resolution sub-wavlength grating structures with 300-nm typical size, which is difficult to replicate.The device gives obvious and rich macro color change effect,and have strong dynamic conversion holographic visual features,which laser holographic technology can not achieve.