Li Chao, Zhou Yun-Song, Wang Huai-Yu
Center for Theoretical Physics, Department of Physics, Capital Normal University, Beijing 100048, China.
Opt Express. 2012 Mar 26;20(7):7726-40. doi: 10.1364/OE.20.007726.
In this paper, we applied the band structure theory to investigate the plasmonic band (PB) structures and optical properties of subwavelength metal/dielectric/metal Bragg waveguides in the near infrared range with either dielectric or geometric modulation. The Bloch wave vector, density of states, slowdown factor, propagation length and transmittance are calculated and analyzed. Both the modulations are in favor of manipulating surface-plasmon-polariton (SPP) waves. For the dielectric modulation, the PB structure is mainly formed by SPP modes and possesses a "regular pattern" in which the bands and gaps have a relatively even distribution. For the geometric modulation, due to the strong transverse scattering, the contributions of higher modes have to be considered and the gap widths have a significant increase compared to the dielectric modulation. A larger slowdown factor may emerge at the band edge; especially for the geometric modulation, the group velocity can be reduced to 1/100 of light, and negative group velocity is observed as well. While inside the bands, the slowdown factor is smaller and the bands are flat. The contribution of each eigenmode to the PB structure is analyzed.
在本文中，我们应用能带结构理论来研究具有介电或几何调制的近红外范围内亚波长金属/介质/金属布拉格波导的等离子体带（PB）结构和光学性质。计算并分析了布洛赫波矢、态密度、慢化因子、传播长度和透射率。两种调制都有利于操纵表面等离激元极化子（SPP）波。对于介电调制，PB结构主要由SPP模式形成，并具有“规则图案”，其中能带和能隙具有相对均匀的分布。对于几何调制，由于强烈的横向散射，必须考虑高阶模式的贡献，并且与介电调制相比，能隙宽度有显著增加。在能带边缘可能会出现更大的慢化因子；特别是对于几何调制，群速度可以降低到光速的1/100，并且还观察到了负群速度。而在能带内部，慢化因子较小且能带是平坦的。分析了每个本征模式对PB结构的贡献。
