基于掠角沉积技术的大面积中红外手性超材料的制备及其偏振态调控特性研究

It is indispensable for control on the polarization of mid-infrared laser during its transmission. Traditional control elements on polarization have big volume, large weight, high cost, and lack of integration. Chiral metamaterials can effectively overcome these shortcomings, which will provide a new way for control on the polarization of mid-infrared laser. At present, chiral metamaterials, in which traditional metals as plasmonic materials were fabricated, are mainly demonstrated in microwave, terahertz and visible regions. Large real parts of permittivities, low chemical stability and other inherent properties of the precious metals affect the control performance of the polarization of the chiral metamaterials. In this project, three types of chiral metamaterials with large areas in which mid-infrared plasmonic materials are induced will be fabricated by utilizing a glancing angle deposition method convenient for mass production. They are six lattice-arranged two-dimensional rotation-shaped mid-infrared chiral metamaterials, six lattice-arranged quasi three-dimensional fan-shaped mid-infrared chiral metamaterials, and six lattice-arranged three-dimensional helix-shaped mid-infrared chiral metamaterials. Their optical activities and circular dichroism will be investigated to obtain their characteristics of polarization control, and their physical mechanisms will be revealed as well. Through the optimization of the structures, we will obtain mid-infrared chiral materials with high-performance polarization control. Our previous studies demonstrated that the mid-infrared chiral metamaterials proposed have obvious advantages. This project will provide a reference for design and production of a new generation of mid-infrared polarization control devices.

偏振态的控制是中红外激光传输过程中不可缺少的环节。传统的中红外激光偏振态控制元件存在体积大、成本高、难以集成等不足，手性超材料能有效克服这些不足，为中红外激光偏振态的控制提供了一条新途径。目前手性超材料主要集中在微波、太赫兹和可见光波段，而且其结构中使用的等离激元材料是传统金属，这些金属在中红外波段介电常数实部大、化学稳定性低等固有性质影响手性超材料对偏振态的控制性能。本项目拟将中红外等离激元材料引入到手性结构中，利用适用于大规模生产的掠角沉积方法，制备三类大面积中红外手性超材料：六方晶格排列两维旋转形、六方晶格排列准三维扇形、六方晶格排列三维螺旋形。从旋光性和圆二向色性两方面研究其对偏振态的调控特性，揭示物理机制。通过结构的优化，获得偏振态调控性能优良的中红外手性超材料。前期研究结果显示本项目提出的中红外手性超材料优势明显，为新一代中红外激光偏振态控制器件的设计和制作提供参考依据。

中红外激光在国防、医疗、通信等方面有着重要的应用。对中红外激光传输的有效控制是决定中红外激光能否得到更好应用的重要因素。对中红外激光偏振态的调控是中红外激光传输控制中的关键环节。传统的中红外激光偏振态调控方法主要包括采用工作在中红外波段的起偏器进行偏振态的直接获取和采用工作在中红外波段的波片进行偏振态调控两种。这些方法明显的不足是所使用的控制元件体积大、成本高、难以集成。手性超材料能有效克服这些不足，为中红外激光偏振态的控制提供了一条新途径。目前手性超材料主要集中在微波、太赫兹和可见光波段，而且其结构中使用的等离激元材料是传统金属，这些金属在中红外波段介电常数实部大、化学稳定性低等固有性质影响手性超材料对偏振态的控制性能。本项目将中红外等离激元材料ITO引入到手性结构中，利用适用于大规模生产的掠角沉积方法，制备三类大面积中红外手性超材料：六方晶格排列两维旋转形、六方晶格排列准三维扇形、六方晶格排列三维螺旋形。研究结果显示：在中红外波段尤其在大气窗口的3-5μm波段，都展示出较强的宽带CD信号。这些由ITO构成的手性结构与由金或银所构成的同样手性结构相比，其CD信号在中红外波段表现出更宽的带宽，显示出更大的优势。而且这些手性结构相较于后者在中红外波段还表现出更强的光学吸收特性。这些特殊性质为中红外手性结构的制备提供了新的思路，在中红外激光器偏振态控制方面具有潜在的应用前景。同时也为中红外波段隐身材料的设计提供一种借鉴。相关研究结果发表在国内外知名期刊论文17篇。