By designing a plasmonic waveguide–slit structure (a nanoslit etched in a silver nanowire) on a silver substrate, an ultrahigh Purcell factor and ultralarge figure of merit (FOM) are numerically predicted. Because of the large field enhancement (>150 times the incident field) and the ultrasmall optical volume (V ≈ 2 × 10⁻⁵λ³) of the resonant mode in the metallic nanoslit, the simulations show that the Purcell factor in the system can reach up to F_P = 1.68 × 10⁵, which is more than ten times the maximum Purcell factor in previous work (by placing metallic nanoparticles on a metal surface with a nanogap). Because of the utilization of a silver substrate rather than the common dielectric substrate, the mode cutoff of the surface plasmon polariton (SPP) waveguide mode is completely eliminated, which provides a large selection range of the nanowire radii to support the resonant mode in the nanoslit. Moreover, the SPP propagation length is significantly increased by more than 30 times. As a result, an ultralarge FOM of 1.40 × 10⁷ is obtained, which is more than 80 times the maximum FOM in previous work where the metallic nanowire is placed on or surrounded by dielectric materials.

中文翻译：

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在金属基板上通过等离子波导-缝隙结构增亮并引导单光子发射

通过在银基板上设计等离子体激元-缝隙结构（在银纳米线中蚀刻的纳米缝隙），可以对超高赛尔因数和超大品质因数（FOM）进行数值预测。由于大的场增强（> 150倍的入射场）的超小体积光及（V  ≈2×10 ^-5 λ ³在金属纳米裂缝谐振模式的）时，模拟显示，在该系统可以赛尔因子达到F _P  = 1.68×10 ⁵，这是以前工作中最大赛尔因子的十倍以上（通过将金属纳米颗粒放置在具有纳米间隙的金属表面上）。由于利用了银基板而不是普通的电介质基板，表面等离子体激元（SPP）波导模式的模式截止被完全消除，这提供了较大的纳米线半径选择范围，以支持纳米缝隙中的共振模式。而且，SPP传播长度显着增加了30倍以上。结果，获得了1.40×10 ⁷的超大FOM ，这是以前的工作的最大FOM的80倍以上，在先前的工作中，金属纳米线被放置在介电材料上或被介电材料包围。