A subwavelength grating with resonant behaviors can be used to exploit security productions with characteristics of anisotropic color variation, i.e., its color has been changed when the grating is rotated on its own plane. In this paper, a novel grating structure with potentials of broadening its spectral bandwidths and improving its color aspects is proposed and its design principles and fabrication methods are also provided. The design of it is completely based on rectangular gratings with a filling factor of 0.5, but the grating regions of fabricated structures have profiles of sinusoidal gratings. Reflection spectra of such two structures are simulated and compared using vector diffraction methods and compared. Moreover, a security grating with unique characteristics of color change has been successfully designed and fabricated, and the changes of color aspects of it have also been verified from both theory and experiment. The proposed structure and its related fabrication methods are feasible in practical application of security and have better values and potentials for mass productions through holographic embossing equipments.
"Short period resonant dual-grating structures for applications to anisotropic color change securities," Optical Engineering 50(4), 048001 (1 April 2011). https://doi.org/10.1117/1.3569852