Greatly enhanced continuous-wave terahertz emission by nano-electrodes in a photoconductive photomixer (Retracted Article) - Tanoto, H; Teng, JH; Wu, QY; Sun, M; Chen, ZN; Maier, SA; Wang, B; Chum, CC; Si, GY; Danner, AJ; Chua, SJ (NATURE PHOTONICS, 2012)