“…In the past decade, the negative refraction phenomenon has attracted tremendous attention, largely being attributed to its remarkable novel physical properties, such as reversal of Snell's law, anomalous Doppler shift, reversed Cerenkov radiation, and the amplification of evanescent wave [1]. By using these properties, scientists studied the possible focusing applications in perfect lens [2], filter [3], sensor [4], invisible cloaking [5], and antenna [6]. A series of artificial composite metamaterials have been developed to achieve negative index materials (NIMs) [2–6].…”