Investigation of ultrafast multi-photon absorption and optical limiting response in a pyrazine-based N-heteroacene

Abstract The ultrafast optical nonlinearity of a pyrazine-based N-heteroacene (Py-0-TQ) is systematically investigated via Z-scan, optical limiting and transient absorption spectrum. Reverse saturable absorption at visible wavelengths is observed. Further study on excited-state kinetics indicates that the strong nonlinear optical (NLO) absorption originates from the cooperating effect between different NLO mechanisms including excited-state absorption (ESA) and two-photon absorption (TPA). Structure-property relation is analyzed, result indicates that the central π-system in Py-0-TQ plays a key role in the cooperating effect via providing a broadband, long-lived ESA and an enhanced TPA as trigger. The experimental and theoretical studies suggest that pyrazine-based N-heteroacene molecules with proper design may have great potential in NLO applications.