Active control of surface plasmon polaritons with phase change materials

Active control of surface plasmon polaritons(SPPs)is highly desired for nanophotonics.Here we employ a phase change material Ge_(2)Sb_(2)Te_(5)(GST)to actively manipulate the propagating direction of SPPs at the telecom wavelength.By utilizing the phase transition-induced refractive index change of GST,coupled with interference effects,a nanoantenna pair containing GST is designed to realize switchable one-way launching of SPPs.Devices based on the nanoantenna pairs are proposed to manipulate SPPs,including the direction tuning of SPP beams,switchable SPP focusing,and switchable cosine–Gauss SPP beam generating.Our design can be employed in compact optical circuits and photonics integration.

复虹现象的实验研究

彩虹是一种常见的大气光学现象,在一定天气条件下,在彩虹的附近还会出现附加的弧形彩色条纹,这就是复虹。目前关于复虹的实验研究还十分有限。本文从集体散射与单体散射两方面对复虹现象进行了实验研究。通过水雾光散射再现了复虹现象,并测量统计了水滴尺寸及其分布对复虹的影响。然后通过单水滴光散射实验,研究了不同照明波长、不同水滴尺寸下的复虹现象,从微观上解释了复虹的形成机理。我们还利用散射理论计算研究了水滴尺寸及其统计分布对复虹效果的影响,计算结果进一步证实了实验结论的正确性。