Four peak and high angle tilted insensitive surface plasmon resonance graphene absorber based on circular etching square window. - Ai, Zhou; Liu, Hongfu; Cheng, Shubo; Zhang, Huafeng; Yi, Zao; Zeng, Qingdong; Wu, Pinghui; Zhang, Jianguo; Tang, Chaojun; Hao, Zhiqiang (Journal of Physics D: Applied Physics, 2025)