Large nonlinear absorption and refraction coefficients of carbon nanotubes estimated from femtosecond Z-scan measurements

TL;DR

This study measures the nonlinear optical properties of single-walled carbon nanotubes using femtosecond Z-scan techniques, revealing significant nonlinear absorption and refraction coefficients.

Contribution

It provides new estimates of the nonlinear absorption coefficient and nonlinear index of carbon nanotubes from femtosecond laser measurements.

Findings

Pulse-width independent saturation absorption observed.

Negative cubic nonlinearity measured.

Estimated nonlinear coefficients: β₀ ≈ 1.4 cm/MW, γ ≈ -5.5×10⁻¹¹ cm²/W.

Abstract

Nonlinear transmission of 80 and 140 femtosecond pulsed light with $0.79 \mu m$ wavelength through single walled carbon nanotubes suspended in water containing sodium dodecyl sulphate is studied. Pulse-width independent saturation absorption and negative cubic nonlinearity are observed, respectively, in open and closed aperture Z-scan experiments. The theoretical expressions derived to analyze the z-dependent transmission in the saturable limit require two photon absorption coefficient $\beta_0\sim$ $1.4 cm/MW$ and a nonlinear index $\gamma \sim -5.5 \times10^{-11} cm^2/W$ to fit the data.