Fig. 2: Realization of different nonlinear crystal classes with the use of different microscopic structures and pole configurations.
From: Mimicking bio-mechanical principles in photonic metamaterials for giant broadband nonlinearity
Each row depicts a potential configuration for the microscopic structures and poling directions that can be used to realize a specific crystal class. The upper and lower metal plates and their overlapped regions are respectively denoted with translucent and vivid yellow colors. The pole configurations inside the overlapped regions are depicted on cross-sections csz (between upper and center metallic layers) and csz’ (between center and lower metallic layers) with “+” (+z poled) and “−” (−z poled) signs and “0” (not poled). The most highly enhanced tensor components (order of [ax,y/hd]3) are highlighted by red squares. Other non-zero terms are indicated with solid and open circles. Identical values are connected with dashed lines. The connected solid and open circles are opposite in sign. Dots indicate zero.
