We present a novel method for fabricating two-dimensional arrays of zinc oxide (ZnO) nanorod patterns. Vertically aligned ZnO nanostructure patterns were synthesized by hydrothermal growth on a two-dimensional seed layer pattern formed by atomic layer deposition. Various characteristics of ZnO seed films were experimentally studied in order to optimize the fabrication of ZnO rod structures in terms of their uniformity and vertical alignment on the two-dimensional-patterned surfaces. Using these ZnO structures as hierarchical electrodes, we demonstrate that localized electric fields in the proximity of ZnO rod patterns can be used for periodic alignment of liquid crystal molecules, resulting in the optical diffraction grating effect. Process conditions for creating ZnO rod patterns that best enhance diffraction efficiency are further discussed. The current study is the first demonstration of hierarchical ZnO rod patterns as electrodes for optical modulation of a medium. We believe this will be beneficial for future optical applications.