Plasmonic focusing was investigated in symmetry broken nanocorrals under linearly polarized illumination. Near-field optical measurements of the perpendicular electric field show that a single subwavelength spot size of 320 nm can be generated. The interference pattern within the corral can be controlled by changing the polarization of optical excitation, and the degree of symmetry breaking. The intensity enhancement factor was investigated using finite-difference time-domain simulations, and confirmed by analytical calculations taking into account the plasmon damping and multiple reflections against the corral wall.

Prof Xing ZHU’s nano-optics group has found a way to focus the SPP wave into a single subwavelength point by using the Symmetry Broken concept. The result was published on-line in Nano Letters on Dec 27, 2010 （Nano Letters, dx.doi.org/10.1021/nl104333n）. This is a partial recent achievements of the group with their publications in Physical Review B, ASC Nano, Applied Physics Letters, Plasmonics etc. Mr. Fang Zheyu, a Ph.D. candidate working at Zhu’s group, is the main contributor, due to his excellent performance during his study, he was elected as “Top 10 Talented Graduate” in 2010.

This work is done by Peking University, National Center for Nanoscience and Technology, Tsinghua University, and Rice University, This work was supported by National Basic Research Program of China (973 Program) , National Natural Science Foundation, and Peking University.