A nanoscale Bragg grating reflector based on the defect metal-insulator-metal (MIM) waveguide is developed and numerically simulated by using the finite element method (FEM). The MIM-based structure promises a highly tunable broad stop-band in transmission spectra. The narrow transmission window is shown to appear in the previous stop-band by changing the certain geometrical parameters. The central wavelengths can be controlled easily by altering the geographical parameters. The development of surface plasmon polarition (SPP) technology in metallic waveguide structures leads to more possibilities of controlling light at deep sub-wavelengths. Its attractive ability of breaking the diffraction limit contributes to the design of optical sensors.

In this paper, a metal–insulator–metal straight waveguide structure with quadrant ring resonators (QRRs) is theoretically presented. The transmission spectra at output ports are studied by the finite element method (FEM). The simulation results show great filtering effects at specific wavelengths. In order to unidirectionally control plasmonic flows at waveguide junctions, the original design has been expanded to T- and X-shaped waveguides with the QRRs. The results reveal that obvious Fano effects can be achieved in T-shaped systems.

2015): Plasmonic tunable filter based on trapezoid resonator waveguide, Journal of Modern Optics,The metal-insulator-metal waveguide structures coupled with a trapezoid cavity are proposed in theory. A variety of transmission features have been found from the simulation results, which is caused by the interference of the plasmonic modes in the trapezoid resonator. The transmission spectra can be effectively modulated by optimizing the geometrical parameters of our configurations such as the height, the upper and bottom edge lengths. Also, the coupling distance possesses great importance on the transmission characteristic. It is found that when the coupling distance is chosen to be around 20 nm, the filter works efficiently. When the trapezoid resonator is attached to the waveguide bus, the bandwidth becomes large. Besides, an effective band-stop filter can be achieved when the bottom edge length is large enough. The finite element method is carried out to verify our designs. We hope our work may open some new avenues for a high-performance plasmonic filter.

2014): A dual-way directional surface-plasmon-polaritons launcher based on asymmetric slanted nanoslits, Journal of Modern Optics,We theoretically design a device composed of two asymmetric slanted nanoslits to achieve the directionality of surface plasmon polaritons (SPPs). With proper inclination of the two slits, the desirable relative phase delay can be obtained. When the structure is illuminated by normal incident light, the SPPs can be controlled to deflect the specific direction due to light interference. The SPPs can be altered to the opposite direction when the illuminating light is changed inversely. We develop another way to tailor the relative phase delay by choosing the specific effective index for each slanted slit. In order to acquire higher directional excitation efficiency, our designs have been extended to periodic structures with the pairs of slanting slits. The finite element method is carried on to verify our designs. The simulations show that the best proportion of the SPP field intensity along two opposite directions reaches to around 30.

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