Midinfrared Third Harmonic Generation from Macroscopically Aligned Ultralong Single-Wall Carbon Nanotubes

TL;DR

This study demonstrates strong midinfrared third harmonic generation from aligned ultralong single-wall carbon nanotubes, revealing a significantly enhanced third-order nonlinear susceptibility and detailed tensor element analysis.

Contribution

First measurement of $ ext{chi}^{(3)}$ in aligned ultralong SWCNTs with detailed tensor element characterization.

Findings

$ ext{chi}^{(3)}$ of SWCNT film is 5.53×10^{-12} esu

Estimated $ ext{chi}^{(3)}$ for dense film is 6.32×10^{-11} esu

Tensor elements show weaker components are about 1/6 of the dominant one

Abstract

We report the observation of strong third harmonic generation from a macroscopic array of aligned ultralong single-wall carbon nanotubes (SWCNTs) with intense midinfrared radiation. Through power-dependent experiments, we determined the absolute value of the third-order nonlinear optical susceptibility, $\chi^{(3)}$, of our SWCNT film to be 5.53 $\times$ 10$^{-12}$ esu, three orders of magnitude larger than that of the fused silica reference we used. Taking account of the filling factor of 8.75% for our SWCNT film, we estimate a $\chi^{(3)}$ of 6.32 $\times$ 10$^{-11}$ esu for a fully dense film. Furthermore, through polarization-dependent experiments, we extracted all the nonzero elements of the $\chi^{(3)}$ tensor, determining the magnitude of the weaker tensor elements to be $\sim$1/6 of that of the dominant $\chi^{(3)}_{zzzz}$ component.