In several years, surface plasmon polaritions (SPPs) have become a very active research area due to the possibility of providing next generation information technology with miniaturization and photonic integration. Generally, scattering structures fabricated on metal film are used to redirect the wave front of SPPs. However, the function of such a method is limited because of the low accuracy and lack of phase modulation. To solve this problem, Prof. Jiasen Zhang proposed a method to implement exact phase and intensity modulation of SPPs, as well as light-SPP coupling. They fabricate coupling structures on metal film and the phase and intensity of SPPs depend on the designed structure. Flexible SPP wave front manipulation and multiple functions can be realized in photonic devices by using this method.

Recently, Prof. Zhang and Mr. Chenglong Zhao, a Ph.D candidate in Prof. Zhang's group, successfully realized a wavelength division multiplexer of SPPs, which is of importance for SPP based integrated device of communication systems. Special arc-formed grating structures that were located on a Rowland circle were designed and fabricated on gold film to realize three functions simultaneously: (1) converting between far-field light and SPPs; (2) dispersing and focusing SPPs with different wavelength; (3) coupling SPPs with different wavelengths into different waveguides. By using this method, one cannot only realize wavelength demultiplexing, but also provide a possible solution to the coupling between SPP based devices and fibers. This work was published on the famous scientific magazine ACS Nano on 6th October online. (http://pubs.acs.org/doi/abs/10.1021/nn101334a, Chenglong Zhao and Jiasen Zhang*, ACS Nano, 2010)。