Third-order nonlinear optical response and ultrafast dynamics of tetraoxa[22]porphyrin(2.1.2.1)s

Ultrafast dynamics and third-order nonlinear optical studies of tetraoxa[22]porphyrin(2.1.2.1)s are reported using a single beam Z-scan technique with femtosecond (fs) and nanosecond (ns) pulses at respective near-IR and visible wavelengths. Excited state absorption mediated reverse saturable absorption was observed at 527 nm while two-photon absorption was observed at 800 nm. High nonlinear refractive index coefficient (γ) and nonlinear absorption coefficient (β) values and the fast response times were attributed to the availability of polarizable π-electrons of the cyclic conjugated aromatic porphyrin framework. Our proposed mechanism of third-order nonlinearity was verified using ultrafast transient absorption spectroscopy. With the observed fast electronic nonlinearities the studied molecules are potential candidates for use as optical limiters.