Qi Yiling, Zhang Guoquan
The MOE Key Laboratory of Weak Light Nonlinear Photonics, Nankai University, Tianjin, China.
Opt Express. 2010 Sep 13;18(19):20170-82. doi: 10.1364/OE.18.020170.
We study the linear discrete diffraction characteristics of light in two-dimensional backbone lattices. It is found that, as the refractive index modulation depth of the backbone lattice increases, high-order band gaps become open and broad in sequence, and the allowed band curves of the Floquet-Bloch modes become flat gradually. As a result, the diffraction pattern at the exit face converges gradually for both the on-site and off-site excitation cases. Particularly, when the refractive index modulation depth of the backbone lattice is high enough, for example, on the order of 0.01 for a square lattice, the light wave propagating in the backbone lattice will be localized in transverse dimension for both the on-site and off-site excitation cases. This is because only the first several allowed bands with nearly flat band curves are excited in the lattice, and the transverse expansion velocities of the Floquet-Bloch modes in these flat allowed bands approach to zero. Such a linear transverse localization of light may have potential applications in navigating light propagation dynamics and optical signal processing.
我们研究了二维主干晶格中光的线性离散衍射特性。结果发现，随着主干晶格折射率调制深度的增加，高阶带隙依次打开并变宽，弗洛凯 - 布洛赫模式的允许带曲线逐渐变平。因此，对于在位和离位激发情况，出射面处的衍射图样都逐渐收敛。特别地，当主干晶格的折射率调制深度足够高时，例如对于正方形晶格为0.01量级，在位和离位激发情况下，在主干晶格中传播的光波在横向维度上都会被局域化。这是因为晶格中仅激发了具有近乎平坦带曲线的前几个允许带，并且这些平坦允许带中弗洛凯 - 布洛赫模式的横向扩展速度趋近于零。这种光的线性横向局域化在引导光传播动力学和光信号处理方面可能具有潜在应用。
