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The third-order nonlinear optical properties of a series of naphthyl, phenanthrenyl, and pyrenyl substituted porphyrins have been comparatively investigated by performing the femtosecond-pulsed Z-scan measurements. Due to the expanded π system, both pyrenly substituted porphyrin ( 1 ) and phenanthrenly substituted porphyrin ( 2 ) exhibit large two-photon absorption cross sections up to 4.26 × 10 4 GM for 1 and 1.36 × 10 4 GM for 2 at the wavelength of 800 nm. The pyrenly substituted porphyrin ( 1 ) has the most excellent two-photon absorption property because of the intramolecular energy transfer from the excited pyrene moiety to the porphyrin moiety in porphyrin 1 . The results confirm that porphyrins conjugated with external π electronic systems can lead to the significant enhancement in the two-photon absorption cross-section values. This research provides a useful guideline to the design of efficient two-photon absorbing materials.

We report the third-order nonlinear optical properties of the homoleptic bis(phthalocyaninato) rare earth double-decker complex Pr(OOPc)2 (1), the oxidized species [Pr(OOPc)2]+ (2), and the reduced species [Pr(OOPc)2]- (3), by performing the femtosecond-pulsed Z-scan experiments at the wavelength of 800 nm. It is found that the second-order hyperpolarizability in complex molecules decreases in the order of 1>2>3. More interestingly, the observed nonlinear absorption process changes from two-photon absorption in the oxidized 2 to saturable absorption in the reduced 3. The results demonstrate that the nonlinear optical properties of sandwich-type phthalocyanine rare earth complexes could be altered by the redox reaction. Furthermore, the figures of merit of three complexes were evaluated for nonlinear photonic applications in optical limiter, saturable absorber, or all-optical switch.

A series of heteroleptic phthalocyaninato rare earth double-decker complexes owning large two-photon absorption cross-sections were reported. The third-order nonlinear optical properties of these heteroleptic phthalocyaninato complexes were experimentally investigated by the Z-scan technique with application of femtosecond (800 nm) pulse lasers. Due to the highly delocalized π-electron system and intense π-π interactions between the phthalocyaninato macrocycles, all complexes were revealed to exhibit large two-photon absorption cross-sections with the value up to 1.83 × 10 5 GM, which are comparable to those efficient two-photon absorbing materials. The optical limiting behavior of these complexes in chloroform was also investigated by using femtosecond laser pulses. The excellent two-photon absorption properties and optical limiting performance indicate their good application potential in optoelectronic devices.

We develop the Z-scan technique on a saturable absorber under the excitation of radially polarized beams. It is shown that the sensitivity of the Z-scan measurements on a saturable absorber using radially polarized beams has the great improvement compared with those using the scalar light beams such as Gaussian beams, Laguerre-Gaussian beams, and top-hat beams. As the experimental evidence, we investigate the saturable absorption properties of layered WS2 nanosheets in aqueous suspension by performing the radially polarized-beam Z-scan measurements with femtosecond laser pulses in the near infrared region.