Extreme Polarization Anisotropy in Resonant Third‐Harmonic Generation from Aligned Carbon Nanotube Films
Extreme Polarization Anisotropy in Resonant Third‐Harmonic Generation from Aligned Carbon Nanotube Films
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对齐碳纳米管薄膜谐振三次谐波产生中的极端偏振各向异性
DOI：
10.1002/adma.202304082
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发表时间：
2023
影响因子：
29.4
通讯作者：
Tan, Chuan Seng
中科院分区：
文献类型：
--
作者：
Zhu, Song;Li, Wenkai;Yu, Shengjie;Komatsu, Natsumi;Baydin, Andrey;Wang, Fakun;Sun, Fangyuan;Wang, Chongwu;Chen, Wenduo;Tan, Chuan Seng
碳纳米管（CNTs）由于其一维特性而具有极强的电子、热学和光学各向异性。虽然碳纳米管的线性光学性质已经得到了广泛的研究，但非线性光学过程，如频率转换的谐波产生，在碳纳米管中仍未得到广泛的研究，特别是在宏观碳纳米管组件中。在这项工作中，合成了排列和类型分离（半导体和金属）碳纳米管的宏观薄膜，并研究了基波长范围为1.5至2.5µm的薄膜极化相关的三次谐波产生（THG）。两种薄膜都表现出强烈的波长依赖性，强烈的THG信号，通过激子共振增强，并且在1.8µm激发下，三阶非线性光学敏感度分别为2.50 × 10−19m2V−2（半导体碳纳米管）和1.23 × 10−19m2V−2（金属碳纳米管）。此外，通过系统的极化相关THG测量，确定了磁化率张量的所有元素的值，验证了薄膜的宏观一维性质。最后，利用极化THG成像证明了具有良好取向的大尺寸碳纳米管薄膜中的非线性各向异性。这些发现为碳纳米管薄膜在中红外频率转换、非线性光开关、极化脉冲激光器、极化长波探测和高性能各向异性非线性光子器件中的应用提供了前景。
Carbon nanotubes (CNTs) possess extremely anisotropic electronic, thermal, and optical properties owing to their 1D character. While their linear optical properties have been extensively studied, nonlinear optical processes, such as harmonic generation for frequency conversion, remain largely unexplored in CNTs, particularly in macroscopic CNT assemblies. In this work, macroscopic films of aligned and type‐separated (semiconducting and metallic) CNTs are synthesized and polarization‐dependent third‐harmonic generation (THG) from the films with fundamental wavelengths ranging from 1.5 to 2.5 µm is studied. Both films exhibited strongly wavelength‐dependent, intense THG signals, enhanced through exciton resonances, and third‐order nonlinear optical susceptibilities of 2.50 × 10−19m2V−2(semiconducting CNTs) and 1.23 × 10−19m2V−2(metallic CNTs), respectively are found, for 1.8 µm excitation. Further, through systematic polarization‐dependent THG measurements, the values of all elements of the susceptibility tensor are determined, verifying the macroscopically 1D nature of the films. Finally, polarized THG imaging is performed to demonstrate the nonlinear anisotropy in the large‐size CNT film with good alignment. These findings promise applications of aligned CNT films in mid‐infrared frequency conversion, nonlinear optical switching, polarized pulsed lasers, polarized long‐wave detection, and high‐performance anisotropic nonlinear photonic devices.