The life style and economic growth have been deeply changed by the information technology revolution since last middle century. However, as the development of process technology and integrations, the physical limitation of the integrated chips, such as quantum dimension effect and thermal effect already have restrict the advance of the information technology. Photons as a carrier of the information are superior to electrons in bandwidth, density, higher speed, and dissipation. More over, photons could carry intensity, polarization, phase, and frequency information which could break through the limitation of binary system. But since the diffraction limitation, the photonic components and devices can not be fabricated small enough to large-scale integrated. Surface plasmon polariton (SPP) is quanta of collective oscillations of free electrons excited by photons in metal nanostrucrures , which offers a promising way to manipulate light at the nanoscale, even realize the photonic miniaturization. The nano-photonic processor needs to solve the problems of light resource, waveguide, beam splitter, router, plasmon logical and operation component, photon-electric electric-photon converter and photon component. At the present time, the study of nanoplasmonics has become a very competitive field.
  Prof. Hongxing Xu’s group in Institute of Physics, CAS & Beijing National Laboratory for Condensed Matter Physics has been working on this new field for years. They have had a series of progress on nano waveguide and remote detection of single molecule [Nano Lett. 9, 2049, (2009)], nano photon-exciton conversion [Nano Lett. 9, 4168 (2009)], photon circuit and nano waveguide directional emission [Nano Lett. 9, 4383 (2009)] and emission polarization modulated by nano antenna [PNAS 105, 16448 (2008)；ACS Nano 3, 637，(2009)]
Recently, Dr. Zhipeng Li and coworkers in the group find that, when the SPPs on a nanowire launched by exciting one end of the wire using a focused laser emitted from the other end, the emission light is polarization maintained, which has a strong dependence on the shape of the wire ends. The character is correlative to the excitation efficiency and decay rate of different SPP modes (m = 0, m = 1). The mixture rate of different modes and the shape of the wire would affect the emission and polarization of light. They have illuminated this phenomenon theoretically cooperated with Pro. Peter Nordlander in Rice University in USA. This may be useful in applications in nanophotonics, such as chip-to-chip interconnects, or in specific applications, such as quantum cryptography. The study has been published in [Nano Lett. 10, 1831 (2010)].
  Additionally, the doctoral student Yurui Fang and coworkers in the group find that plasmons propagating on branched silver nanowires can be routed into different wire branches and result in light emission from the corresponding wire ends by controlling the polarization of the incident laser light, which can be used as a nano photonic router. Besides, this routing behavior is found to be strongly dependent on the wavelength of light. Thus for certain incident polarizations, light of different wavelength will be routed into different branches without interfering. So the branched nanowire can serve as a controllable router and multiplexer in integrated plasmonic circuits. This finding may have numerous applications in future nanophotonic devices, circuits, and networks. The study has been published in [Nano Letters 10, 1950 (2010)].
  This study was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology of China, and knowledge innovation project of Chinese Academy of Sciences.