Saturable absorption and nonlinear refraction in free-standing carbon nanotube film: Theory and experiment

V. V. Vanyukov*, M. V. Shuba*, A. G. Nasibulin, Y. P. Svirko, P. P. Kuzhir, G. M. Mikheev

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The nonlinear absorption and refraction of free-standing films made of single-walled carbon nanotubes (SWNTs) have been investigated experimentally and theoretically. By solving the quantum kinetic equations that take into account both the intra- and interband transitions, we obtain the analytical expression for the SWNT nonlinear conductivity. The nonlinear absorption coefficient and saturation intensity of the film comprising randomly orientated SWNTs have been calculated in a broad spectral range spanning over M11, S11, and S22 absorption bands. The effects of the laser pulse duration and dynamic Burstein−Moss shift on the saturation intensity have been revealed. We demonstrate in the experiment that, under irradiation with femtosecond laser pulses, the absorption modulation depth of SWNT film at resonance wavelength 1375 nm is as high as 30%. The observed saturation intensity minimum is red-shifted with respect to the absorption maximum due to the dynamic Burstein−Moss shift. The saturation intensity within the S22 band is 26−fold lower than that out of the band at 795 nm. The closed-aperture z-scan measurements reveal the negative nonlinear refractive index n2 = −3.1 × 10−12 cm2/W at 795 nm.

Original languageEnglish
Pages (from-to)509-519
Number of pages11
JournalCarbon
Volume186
Early online date19 Oct 2021
DOIs
Publication statusPublished - Jan 2022
MoE publication typeA1 Journal article-refereed

Keywords

  • Dynamic Burstein–Moss shift
  • Free-standing carbon nanotube film
  • Nonlinear refraction
  • Saturable absorption
  • Surface conductivity

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