Ultrafast electron dynamics and cubic optical nonlinearity of free standing thin film of double walled carbon nanotubes

TL;DR

This study investigates the ultrafast electron dynamics and cubic optical nonlinearity of free-standing double-walled carbon nanotube films using pump-probe and z-scan techniques, revealing rapid photobleaching and significant nonlinear susceptibility.

Contribution

It provides new measurements of ultrafast electron relaxation and third-order nonlinear susceptibility in double-walled carbon nanotubes, highlighting their potential for nonlinear optical applications.

Findings

Ultrafast photobleaching with a 97 fs decay time.

Observation of saturation absorption and negative cubic nonlinearity.

Quantitative estimates of real and imaginary parts of third-order susceptibility.

Abstract

Ultrafast degenerate pump-probe experiments performed on a free standing film of double walled carbon nanotubes near the first metallic transition energy of outer tube show ultrafast ($97 fs$) photobleaching followed by a photo-induced absorption with a slow relaxation of $1.8 ps$. Femtosecond closed and open aperture z-scan experiments carried out at the same excitation energy show saturation absorption and negative cubic nonlinearity. From these measurements, real and imaginary part of the third order nonlinear susceptibility are estimated to be Re($\chi^{(3)}) \sim -2.2 \times 10 ^{-9} esu$ and Im($\chi^{(3)}) \sim 1.1 \times 10 ^{-11} esu$.