芯片级对齐的具有巨大小二倍频生成的螺旋碳纳米管
Chip-Scale Aligned Chiral Carbon Nanotubes Exhibiting Giant Second Harmonic Generation
AI总结：
该研究通过合成大规模对齐的单对映体螺旋碳纳米管薄膜，实现了对螺旋碳纳米管内在手性和反演对称性破缺的利用，观测到巨大小二倍频生成，展示了其在可扩展的螺旋碳纳米管电子和非线性光子学中的应用潜力。
摘要：
螺旋碳纳米管（CNTs）是直接带隙半导体，其光学性质由一维激子决定，具有巨大的振子强度。每种螺旋CNTs都有左手和右手对映体的配对，性质几乎相同，但对映体依赖现象可能在非线性光学过程中出现。理论研究表明螺旋CNTs具有强的二阶非线性，但由于缺乏宏观有序的单对映体螺旋CNTs组装，尚未有实验定量验证。本文报告了合成厘米级、密集排列、对齐的单对映体螺旋CNTs薄膜，与微加工兼容。我们观察到螺旋CNTs薄膜的巨大小二倍频生成（SHG）发射，源自其原子结构的内在手性和反演对称性破缺。所观测到的非线性电容率为4.9×10² pm/V，在1030 nm泵浦波长下，对应最低能级的激发子共振，表明完美对齐的CNT晶体的χ_xyz为1.6×10³ pm/V。基于多体理论的计算正确估计了此类激子增强的光学非线性光谱和幅度。这些结果对可扩展的螺旋碳纳米管电子和非线性光子学的发展具有前景。
英文摘要：
Chiral carbon nanotubes (CNTs) are direct-gap semiconductors with optical properties governed by one-dimensional excitons with enormous oscillator strengths. Each species of chiral CNTs has an enantiomeric pair of left- and right-handed CNTs with nearly identical properties, but enantiomer-dependent phenomena can emerge, especially in nonlinear optical processes. Theoretical studies have predicted strong second-order nonlinearities in chiral CNTs, but no experimental quantitative verification has been reported due to the lack of macroscopically ordered assemblies of single-enantiomer chiral CNTs. Here, we report the synthesis of centimeter-scale, densely packed, aligned single-enantiomer chiral CNT films that are microfabrication-compatible. We observe giant second harmonic generation (SHG) emission from the chiral CNT film, which originates from the intrinsic chirality and inversion symmetry breaking of the atomic structure of chiral CNTs. The observed nonlinear susceptibility of the as-fabricated film reaches $4.9\times 10^2$\,pm/V at a pump wavelength of 1030\,nm, corresponding to the lowest-energy excitonic resonance, indicating $χ_{xyz} = 1.6\times 10^3$\,pm/V for a perfectly aligned CNT crystal. Our calculations based on many-body theory correctly estimate the spectrum and magnitude of such excitonically enhanced optical nonlinearity. These results are promising for the development of scalable chiral-CNT electronics and nonlinear photonics.
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