Design and experimental investigation of interdigitated electrode architecture for tunable liquid crystal-based metasurfaces with rapid responses

In this paper, an interdigitated electrode architecture is investigated, which can be used to tune the permittivity of liquid crystal (LC) in metasurfaces with rapid responses. The interdigitated electrodes are composed of two groups of cross-distributed comb grids, where external bias voltages can be applied to each group of comb grids. By continuously adjusting the bias voltages through the grids, the orientation of the liquid crystal molecules can be dynamically controlled due to the excited electrostatic field. Hence the permittivity of the LC and the electromagnetic responses of the metasurface can be tuned arbitrarily by the external biasing. Three kinds of interdigitated electrodes with different fitting ratios were developed to explore the working of the interdigitated electrode architecture. The response time of these interdigitated electrodes and their influence on frequency tunability were analyzed in detail. The measured absorption spectra of interdigitated electrodes with 7, 9, and 11 grids per unit cell with identical periodicity indicate that the fill density of comb grids has a negligible effect on the frequency tunability. However, the fill density has a significant impact on the response time of the LC metamaterial in the interdigitated electrodes. Moreover, the response time was further reduced by 65% with the increase in the number of grids. The proposed architecture and its design provide new insight into developing tunable LC metasurfaces with rapid responses.