Nonlinear absorption of tetrathiafulvalene radical cation (TTF+) based charge transfer (CT) aggregates in PMMA

TL;DR

This study investigates the nonlinear optical absorption properties of TTF+ charge transfer aggregates embedded in a PMMA matrix using femtosecond Z-scan measurements around 800 nm, revealing ultrafast CT state dynamics.

Contribution

It introduces a novel fitting model for saturated absorption profiles that accounts for high saturation regimes and estimates the CT state lifetime in the hundreds of femtoseconds.

Findings

Ultrafast CT state lifetime estimated at hundreds of femtoseconds.

Nonlinear absorption behavior characterized using femtosecond Z-scan technique.

Model fitting provides insights into high saturation regime dynamics.

Abstract

Nolinear Absorption of CT TFF+ aggregates in PMMA matrix was studied with resonant excitation around 800 nm in the femtoseconds regime with the Z-Scan technique with 100 Hz pulse repetition rate. The saturated absorption profiles were fitted with a prepared formula based on steady state rate equations for a homogeneous ensemble of two levels systems, thin samples and quasi monochromatic field without the usual assumption of low saturation regime. The lifetime of the CT state, with the use of this model was estimated in hundred of fs, of the same order of magnitude of the exciting pulse.