Plasmonic cavity made of defect in an array of asymmetric T-shaped structures

We study plasmonic cavity in a 1D array of asymmetric T-shaped plasmonic gratings. The asymmetric T-shaped plasmonic grating contains a silver bigrating structure. The first metallic grating contains the post of the T-shaped structure embedded in SiO2 and the second metallic grating is the cap of the T-shaped structure embedded in air. The bigrating can open a large plasmonic band gap (~ 0.15eV). We introduce a defect in a 1D array of asymmetric T-shaped structure by reducing the width of the cap in one line or in multiple lines. We have studied two kinds of defects. The first defect is a missing line from the T-shaped grating and it has a relatively low quality factor of 64 and a very small effective mode area [0.026 (λ/n)2]. The second one is done by removing or shifting more than one line from the T-shaped grating to make a gentler confinement and it leads to an enhancement of the quality factor (~200) and a slight increase in the effective mode area to [0.0375 (λ/n)2].

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