Elucidating the ultrafast optical limiting properties and its photo-physical mechanism in twistacenes compounds

Nonlinear optical materials with high optical limiting (OL) response have raised much attention due to their potential application in laser protection. Meanwhile, for most optical limiting materials, it is difficult to combine both strong nonlinear absorption and high linear transmittance. Here, the nonlinear properties, especially OL performance in a series of functionalized twistacene derivatives are systematically investigated, indicating that both the as-prepared compounds, 10,15-di-tert-butyl-8-phenyldibenzo[hi,mn]indeno[1,2,3-de]tetracene (S2) and 4,18-di-tert-butyl-15-methyl-16-phenyl-15H-pyreno[4′,5′:3,4]fluoreno[1,9-ab]carbazole (S3) present significant OL response with extremely high transmittance and low thresholds. Furthermore, S3 bearing a maximum extended π-conjugation, exhibits giant OL performance that can respond to femtosecond, picosecond and nanosecond laser pulses simultaneously. The research may demonstrate the potential application of these compounds in laser protection towards ultrashort pulses.