Hanhong Liu(刘汉宏), Yuhui Wang(王宇辉), Langran Deng(邓朗然), Guangzhi Chen(陈广志), Aixin Chen(陈爱新), Zhizhang Chen(陈志璋), Shunchuan Yang(杨顺川). Towards the Development of a Three-Dimensional SBP-SAT FDTD Method: Subgridding Implementation