Ultrafast absorptive and refractive nonlinearities in multi-walled carbon nanotube film

TL;DR

This study demonstrates ultrafast absorptive and refractive nonlinearities in multi-walled carbon nanotube films using femtosecond laser pulses, revealing negative cubic nonlinearities and a 2 ps relaxation time.

Contribution

It provides the first detailed measurement of third-order nonlinear susceptibility and relaxation dynamics in multi-walled carbon nanotube films at visible wavelengths.

Findings

Negative cubic nonlinearities observed in the film.

Third-order nonlinear susceptibility of about 10^-11 esu.

Relaxation time of 2 ps measured via pump-probe.

Abstract

By using femtosecond laser pulses at a wavelength range from 720 to 780 nm, we have observed absorptive and refractive nonlinearities in a film of multi-walled carbon nanotubes grown mainly along the direction perpendicular to the surface of quartz substrate. The Z-scans show that both absorptive and refractive nonlinearities are of negative and cubic nature in the laser irradiance range from a few to 300 GW/cm^2. The magnitude of the third-order nonlinear susceptibility,chi-(3), is of an order of 10^-11 esu. The degenerate pump-probe measurement reveals a relaxation time of 2 ps.