Reflection Phase Modulation of Subwavelength Gold Gratings with Asymmetric Boundaries

In this study, the subwavelength grating multilayer structure with asymmetric boundary conditions is investigated using scattering matrix theory. A formal expression linking the reflection phase to the dielectric constant of the grating boundary medium is derived. Based on this expression, simulation experiments are conducted using the timedomain finite difference method to validate the pre designed silicon-based liquid crystal structure embedded with subwavelength gold gratings(G-LCoS). Through continuous optimization of the asymmetric boundary conditions of the subwavelength gold gratings, nearly 2p phase modulation across multiple wavelengths in the visible spectrum is realized via the G-LCoS. The formal expression and optimization process detailed in this paper offer reference for the design of devices with dynamic asymmetric boundary conditions, particularly complex amplitude modulation devices featuring nano/ micro-scale structures. Additionally, this study contributes to a deeper understanding of these devices in terms of their physical mechanisms to a certain extent.