Third- and Fifth-Order Nonlinear Optical Response of a TICT/Stilbene Hybrid Chromophore

Twisted intramolecular charge transfer (TICT) chromophores exhibit a promising third-order nonlinear optical (NLO) response, γ, which is potentially useful for all-optical switching. Here we explore the third- and fifth-order NLO response of a newly synthesized chromophore, TMC-3′, which incorporates both stilbene and TICT motifs with optical function. Solution Z-scan measurements in CH2Cl2 reveal modest two-photon absorptions (2PA) at 1100 and 800 nm (σ2PA > 80 GM), and two contributions to the nonlinear refraction. The first component is attributed to the third-order bound-electronic response, while the second is assigned to a fifth-order process involving 2PA induced excited state refraction (2PA-ESR). Quantum computation suggests that the differences between the present work and previous studies lie primarily in the addition of the stilbene related states, as well as the increase in ground state dipole moment. This work yields insight into the third- and fifth-order NLO response of TICT chromophores and demonstrates that subtle structural modifications significantly impact their functionality.