均匀等离子体光栅的色散特性研究

最近研究表明，两束交叉激光脉冲在等离子体中传播时，可以诱导生成周期等离子体密度调制(或称等离子体布拉格光栅). 分别利用传输矩阵法和耦合模理论，推导了激光斜入射时等离子体光栅的色散关系. 两种方法均表明，均匀等离子体光栅存在着光子带隙结构，并且在带隙附近有强烈的色散. 当激光斜入射时，带隙结构会呈现不同的偏振特性：S偏振光的带隙宽度随着入射角的增大而逐渐变宽，而P偏振光的带隙宽度随着入射角的增大先迅速变窄，在布儒斯特角入射时带隙消失，然后又随着入射角的增大而迅速变宽. 超宽的光子带隙和超高的激光损伤阈值，使得等离子体光栅有望成为一种新型的操纵强激光脉冲的光子器件. 关键词： 等离子体光栅 传输矩阵法 耦合模理论 光子带隙

Investigation on the dispersion characteristics of a uniform plasma grating

Recently, the plasma Bragg gratings induced by two intersecting laser pulses has been predicted theoretically. The dispersion relation of uniform plasma gratings under the oblique incidence of a light wave is investigated with the transfer-matrix method and the coupled-mode theory. Both approaches show that such plasma gratings exhibit a photonic band gap, near which strong dispersion appears. The photonic band gap has different polarization characteristics when the light wave is obliquely incident on the plasma grating. With the increase of the incident angle, the band gap for an S-polarized wave increases gradually, while that for a P-polarized wave decreases first rapidly, then vanishes when it approaches the Brewster angle, and finally becomes wide with the further increase of the incident angle. Since the plasma grating has an ultrabroad photonic band gap and can support an ultrahigh damage threshold of incident light waves, it has the potential to be a novel photonic device to manipulate extremely intense laser pulses.