近红外可调辐射方向的非线性光学天线

Nonlinear Antennas with Tunable Radiation Patterns in Near Infrared

目前研究人员提出了各种光学天线以线性方式控制辐射图,而较大的非线性效应可以引起天线的折射率的变化,从而改变辐射方向图。通过修正电子的有效质量进而完善Drude模型,可得到氧化铟锡(ITO)的非线性折射率与频率和强度的函数关系,进而可知由ITO制成的纳米天线会表现出极大的光学Kerr效应。本文研究了ITO天线的线性和非线性响应。利用ITO的Kerr效应控制天线的辐射方向图。基于该模型,设计了一种非线性光学天线,实现了覆盖近红外波段(1000~1650 nm)的可调谐辐射方向图。进一步,基于ITO和介电材料硅(Si)设计了一种杂化的非线性光学天线。该杂化天线可以更好地利用ITO的强Kerr效应,可以较大程度上对光场辐射进行调控。该工作突破了新型非线性材料的强Kerr效应仅局限于特定共振频率点或者零折射率点这一特点。本研究提供一种用于超快动态控制超材料的新颖方法,可应用于光束转向和光学调制等。

Various optical antennas have been proposed to control the radiation pattern in a linear manner.Furthermore,the larger nonlinearity will play a vital role,and will change the refractive index of the antenna,thereby changing the radiation pattern.By modifying the effective mass of electrons in Drude model,it can be obtained that the refractive index of ITO film changes with the optical field intensity,and provides the nonlinear refractive index as a function of frequency and intensity.Nanoantennas made of indium tin oxide(ITO)will exhibit strong Kerr effect.The linear and nonlinear responses of ITO antennas was studied,the Kerr effect of ITO was used to control the radiation pattern of the antenna.Based on this model,a nonlinear optical antenna was designed to achieve tunable radiation pattern covering a broad near infrared band(1000 nm to 1650 nm).Moreover,a hybrid nonlinear antenna was demonstrated,composed of ITO and silicon(Si),which can control the radiation pattern more efficiency.This work breaks through the limitation that the strong nonlinear refractive index coefficient of nonlinear material only occurs at specific resonance frequency or the zero refractive index point.Our study provides a novel approach toward ultrafast dynamical control of metamaterials,for applications such as beam steering and optical modulation.