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9 October 2012 A fork-shaped plasmonic device with polarization-controllable optical confinement
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It is shown that fork-shaped plasmonic gratings can display a hybrid mode that features both plasmonic mode (TMmode) and dielectric mode (TE-mode) characteristics with wide range of tunable group velocities. A dielectric gap is introduced in the middle of metallic grating and it is found that this gap plays an important role in controlling the TE-TM mode coupling. By controlling the polarization angle we can switch from plasmonic mode to dielectric mode. Thus, a new scheme for manipulating the optical confinement by using a polarizer is realized. (see Figure) We can combine the plasmonic mode and dielectric mode to reduce the intrinsic loss of Plasmon-polariton due to the free-carrier absorption in the conducting material with the same degree of confinement. The fork structure provides an easier way to control the group velocity in a wide range. The dispersion relations were calculated by using Rigorous Coupled Wave Analysis. We obtain tunable group velocities ranging from 0.2c to almost zero (i.e. achieving localized Surface Plasmon-polariton) and from 0.05c to 0.3c by varying the pillar and dielectric (made of Si3N4) thicknesses respectively. This fork structure is expected to have applications in surface plasmon polariton (SPP) mixed with guided-mode based optical devices, such as optical buffering, hybrid waveguides, splitters and lasers and especially for applications requiring slow light propagation.
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Mohammed Nadhim Abbas, M. H. Shih, and Yia-Chung Chang "A fork-shaped plasmonic device with polarization-controllable optical confinement", Proc. SPIE 8457, Plasmonics: Metallic Nanostructures and Their Optical Properties X, 84572E (9 October 2012);

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