A phenothiazine–silver hybrid system exhibiting switching and photo-induced enhancement in nonlinear optical absorption

Abstract

Engineering novel organic–inorganic hybrid materials for optical limiters and optical switches towards various photonic applications has recently gained great interest as they exhibit low energy transitions, higher molecular hyperpolarizability and fast switching of nonlinear optical behavior. But many of these systems exhibit poor efficiency at elevated input fluence due to the lack of stability against light-induced deterioration, imposing a restriction on the use of higher powers. Here we report the synthesis of an organo-metallic hybrid system (phenothiazine (PTZ)–silver (Ag)) using a pulsed laser ablation technique and its third-order nonlinear optical characterizations by single beam Z scan in a short pulse regime using a Q switched Nd:YAG laser (7 ns, 10 Hz) at 532 nm. The production of nanoparticles by ablation and their reduction as well as stabilization by photo-ionized PTZ molecules are simultaneously carried out within the same setup. The nonlinear absorption (NLA) coefficient is found to be approximately two orders of magnitude higher upon hybrid system formation when compared with that of pristine PTZ. Moreover, the fact to be emphasized here is that, by forming a hybrid system with Ag NPs, we could induce nonlinearity in PTZ at a lower excitation intensity at which pristine PTZ could not show any nonlinearity. The charge transfer between PTZ and Ag NPs as well as the local field effect induced due to surface plasmon resonance (SPR) of Ag NPs plays a crucial role in the observed enhancement. Both the composites and the pristine compounds show self-defocusing behavior and a significant improvement is also observed in the nonlinear refraction (NLR) coefficient of the hybrid system. The enhanced NLA along with the high stability makes this hybrid system an excellent candidate for nonlinear optical applications under short pulse excitation.