Understanding the effect of bound excitons on two photon absorption process in anatase TiO2 nanospheres using ultrafast pulses

Abstract

Nanoparticles of Titanium dioxide [Formula: see text] with its unique optical and electronic characteristics is an important material for photochemical catalysis. The efficiency of catalytic activity of [Formula: see text] anatase nanostructures is greatly influenced by the photo-generated bound excitons. It is found that the interaction of bound excitons generated in [Formula: see text] enhances the cubic nonlinearity of the system due to strong oscillation of photo-generated bound excitons. The trapped electron hole pair concentration is directly proportional to the photocatalytic efficiency of the [Formula: see text] anatase nanostructures. In our report, we show how these photo-generated bound excitons play a significant role in origin of third-order optical nonlinearities. In particular, we have measured large phase shift and seen two photon absorption process through closed and open aperture Z-scan, respectively, using femtosecond pulses at 532[Formula: see text]nm.

Enhanced nonlinear optical performance of perovskite films passivated by porphyrin derivatives

“…76,77 On the other hand, photogenerated bound excitons are confined within the perovskite inorganic octahedral lattice slab after passivation, which could result in a large exciton binding energy in combination with the photoelectric field, leading to an enhanced SA response. 78 Regarding the data in Table 2, the β values of MAPbI 3 /ZnP1 and MAPbI 3 /ZnP3 films are nearly two times larger than that of the pristine MAPbI 3 film as well as higher than those of similar perovskite materials and some two-dimensional materials (Table S1, ESI†), exhibiting distinguished NLO absorption performance. Even if taking into account the scalability of the pulse width, synthetic perovskite materials in our work are still competitive, 79 which are anticipated to be promising application candidates for constructing high-performance NLO devices.…”

Self-consistent quantum field theory for the characterization of complex random media by short laser pulses

“…0 is the dielectric constant in free space, is defined in the literature as the material specific dielectric coefficient = 1 + χ, c is the speed of light. Higher-order processes, for instance Kerr media [37] with the dielectric susceptibility χ (2) [82,83], are in electrodynamics classified by the dependency of P to the electrical field E [87] without loss of generality. It is well known that both the conductivity as well as the susceptibility contribute to the permittivity, so in general Im = Im(χ) + Re(σ/ω) is given.…”

“…The random medium can be comprised of ensembles of arbitrarily shaped particles as well as correlated disorder and glassy systems in principle [79]. We focus in this work on independent non-conserving Mie scatterers [80,81] in strongly scattering ensembles of a high filling fraction, for instance mono-and polydisperse complex TiO 2 powders [82,83]. Such ensembles are well known for showing a pronounced Mie signature in their transport characteristics such as the scattering mean free path as it has been determined experimentally also by coherent backscattering for optically passive systems [1,16,41], Fig.…”

Donor–π–Acceptor Porphyrin-Assisted Bifunctional Defect Passivation for Enhanced Temporal Domain-/Wavelength-Dependent Nonlinear Absorption Properties in Perovskite Films

“…The PET between porphyrin and perovskite via acetylenic π-conjugated bridges is also favorable for enhancing SA properties. Moreover, photogenerated free carriers can be confined tightly within the inorganic octahedral lattice slab of perovskite through porphyrin passivation . Large exciton binding energies are realized through this confinement in conjunction with the photoelectric field, which synergistically enhances the NLO response of perovskites.…”