Strong near-infrared and ultrafast femtosecond nonlinearities of a covalently-linked triply-fused porphyrin dimer-SWCNT nanohybrid

Functional materials displaying large ultrafast third-order optical nonlinearities across a wide spectral region and broad temporal domain are required for all-optical signal processing. Particularly desirable is nonlinear optical (NLO) activity at near-infrared (NIR) wavelengths with femtosecond pulses. Herein the first triply-fused porphyrin dimer (TFP)-functionalized single-walled carbon nanotube (SWCNT) nanohybrid was successfully constructed by covalently grafting TFPs onto SWCNT. The results of Z-scan techniques demonstrate that the newly obtained TFP-SWCNT nanohybrid was found with a strong NLO performance under both nanosecond and femtosecond irradiation. In the nanosecond regime, an enhancement in optical limiting (OL) of the TFP-SWCNT nanohybrid is seen at 532 nm when compared with the performance of porphyrin monomer-functionalized SWCNT nanohybrid Por-SWCNT. Under femtosecond irradiation, the TFP-SWCNT nanohybrid exhibits a particularly strong OL effect with a giant two-photon absorption (TPA) cross section value (ca. 15,500 GM) at 800 nm pulses that mainly stems from intense TPA of TFP, in sharp contrast to the Por-SWCNT nanohybrid which exhibits only saturable absorption under identical irradiation. These results demonstrate that the newly-developed TFP-SWCNT nanohybrid is a very promising OL candidate for practical applications across wide spectral and temporal domains, and that covalently functionalizing carbon-based materials with triply-fused chromophores may be a useful approach to engineering adaptable photonic devices with broad-ranging NLO activity.