1. National Lab of Color Science and Engineering，School of Information Science and Technology Beijing Institute of Technology，Beijing 100081，China 2. College of Packing & Printing Engineering, Tianjin University of Science & Technology, Tianjin 300222, China
Abstract：A security grating structure, intercross cascaded dual-layer resonant sub-wavelength grating structure, is presented. It can broaden the resonant wavelength width of resonant sub-wavelength gratings and obtain the better optical variable effect. The full-width-at-half-maximum(FWHM) broadening mechanism of security grating structures is analyzed .The FWHM is dependent on the energy coupled into the grating waveguide layer. The grating structure parameters are optimized and designed. The resonance performance and grating fabrication tolerances are also studied numerically using the vector diffraction theory (the rigorous coupled wave theory). Simulation results indicate that the value of the spectral resonant peak for the security grating structure is not decreased as the incident angle increases or decreases and the maximum FWHM of different depth of grating grooves is about seven times that of the basic resonant grating structure. The resonant dual grating waveguide structure is a kind of security grating configuration with the potential to achieve higher industry application value and its resonance performance is not sensitive to manufacture errors.
[1] Gale M T，Knop K，Morf R. Proc. of SPIE，1990，1210：83. [2] CHEN Yong-li，ZHAO Da-zun，ZHANG Jing-fang，et al(陈永利，赵达尊，张静方，等). Transactions of Beijing Institute of Technology(北京理工大学学报)，2007，27(6)：527. [3] Tompkin W R，Staub B R. U. S. Patent，6870678，2005. [4] Souparis H. U. S. Patent，6943952，2005. [5] Thurman S T，Morris G M. Appl. Opt.，2003，42(16)：3225. [6] Lenaerts C，Moreau V，Lion Y F et al. Opt. Eng. ，2004，43(11): 2631. [7] Selle C K A，Bader M A，Marowsky G. J. Opt. Soc. Am. B，2004，21(6): 1127. [8] Jacob E K，Dunn S T，Moharam M G. Appl. Opt.，2002，41(7): 1241. [9] Jacob D K，Dunn S T，Moharam M G. J. Opt. Soc. Am. 2000，17(7): 1241. [10] Jacob D K，Dunn S C，Moharam M G. J. Opt. Soc. Am. A，2001，18(9): 2109. [11] Gaylord T K，Moharam M G. Proc. of the IEEE，1985，73: 894. [12] QIN Xi-yun，LI Jun-hui，YANG Yu-hong，et al(秦西云，李军会，杨宇虹，等). Spectroscopy and Spectral Analysis (光谱学与光谱分析)，2007，27(2)：411. [13] Tayeb G，Gralak B，Enoch S. Optics & Photonics News，2003，2: 40.
