理想同心介质球纳米喷流特性

Near field distribution of photonic nanojet formed by perfectly concentric core-shell structure

利用有限时域差分方法,对核壳结构进行了模拟研究,得到内核折射率以及内核半径对聚焦光斑纳米喷流特性的影响。研究表明:在内核半径不变的情况下,当内核相对折射率较低时,入射光能量主要集中在内核与外壳层交界区域,此时光波能量有很大一部分处于非聚焦的旁瓣中;当内核折射率超过外层,可以在核壳结构背光面形成双增强点;在内核相对折射率不变的情况下,通过改变内核半径实现了对内、外核聚焦点位置的主动控制。

Obtaining spatially high-resolution optical information effectively through overcoming the restriction of the dif- fraction limit in the optical field system has become an important research topic in the area of nanophotonics. We applied finite difference time domain （FDTD） method to study the characteristics of the focused spot nanometer jet formed by a core shell struc- ture with various core refractive index and core radius. Results show that under the circumstance of the core radius unchanged, while the core had low refractive index, the incident energy was concentrated in the boundary region of the core and the shell lay- er, at the same time, large amount of energy injects into the side lobe; when the refractive index of the core was larger than that of the outer shell, double enhanced points at the end of the core shell structure could be formed; as the core＇s relative refractive index was unchanged, active control of internal and external core focus point location by changing the core radius was achieved.