亚波长金属缝中的拍

The Beat in a Subwavelength Metal Slit

用时域有限差分法研究两列频率相近的光入射到金属亚波长狭缝中的情况,发现理想金属狭缝中磁场会形成拍,这与真空中情况一致.但是实际金属(银)狭缝中的磁场与真空情况有较大不同,主要是振幅大为降低,超过了对实际金属吸收的预期.这是因为亚波长狭缝中表面等离子体波在靠近金属壁处形成很强的电场,能量更多的以电场形式表现,磁场被削弱.

The electromagnetic wave in metal subwavelength slit excited by two incident waves with the similar frequencies was investigated by using of the finite difference time domain （FDTD） method. Our results show that, in the perfect metal slit, the magnetic field represents the ＂beat＂ characteristics, just as the superposed field of the two corresponding waves in vacuum. In the silver slit, the magnetic field is quite different from that in the perfect slit. This is because the surface plasmon polariton wave in real metal slit has been excited with the very strong electric field, which taken the majority energy and depressed the corresponding magnetic field.