Femtosecond Third-Order Non-Linear Optical Properties of Unconstrained Green Fluorescence Protein Chromophores

We report herein results on the third-order non-linear optical (NLO) properties of four structurally unconstrained green fluorescence protein (GFP) chromophores, namely, 1 , 2 3 and 4 . Using experimental techniques theoretical calculations such as UV–visible spectroscopy, density functional theory (DFT), time-dependent (TDDFT), Z-scan techniques, we have investigated linear absorption, ultrafast non-resonant non-linearities, onset optical-limiting thresholds these benzylidenedimethylimidazolinone (BDI) dyes. The measurements were performed at a wavelength 800 nm with ∼70 femtosecond (fs) pulses. witnessed strong reverse saturable absorption (fitted to three-photon absorption) for all molecules fs pulse excitation. valley–peak curves obtained from closed-aperture technique revealed positive refractive index (self-focusing) nature molecules. evaluated various NLO coefficients (second hyperpolarizability, γ ∼10 –33 esu), which found be larger than those similar reported in recent literature.