Nanomechanical Plasmonic Filter Based on Grating-Assisted Gap Plasmon Waveguide

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We propose and numerically analyze a tunable nanomechanical plasmonic filter based on Bragg-grating-assisted gold-air-gold gap plasmon (GP) waveguide. Bragg grating is formed by introducing periodical grooves on lower gold layers, and the air-gap size is mechanically changeable by electrostatically actuating the upper gold layer. Using the sensitivity of the GP mode to the gap size, the tunability of the proposed filter is realized by changing the gap size. By introducing a phase shift in the Bragg grating, sharp transmission peak with a quality factor of 35 is achieved within the stopband, which could be tuned over a wide wavelength range by a small change in the gap size. The proposed filter can be applied in the tunable plasmonic devices for future integrated optical circuits.