Synthesis, Characterization, and Second Harmonic Generation of Multiferroic Iron-Doped Lithium Niobate Powders

Random granular media can exhibit characteristics that are often related to ordered media. In the present work, this feature is observed in the polarized Second Harmonic Generation (SHG) response from reduced iron-doped lithium niobate (LN:Fe) powders, which is an unexpected effect due to multiple scattering. In addition, the subsisting-order properties of the powders can be further controlled by magnetic induction to tailor the SHG response. The samples are characterized by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and confocal Raman Spectroscopy. The SHG response in the absence and presence of an external static magnetic field is then studied as the fundamental beam focus is translated from air into the powder. The SHG intensity polarization state is studied as a function of the linear polarization of the fundamental beam at the focus depth position, where the maximum SHG recorded intensity is observed. These results demonstrate that the SHG response of LN:Fe powders can be modified by post-thermal treatment in a reducing atmosphere for photonic applications. Second Harmonic Generation from iron-doped Lithium Niobate powders is investigated as a function of the Fe doping rate, a post-thermal treatment, and the incident polarization, revealing that a reducing atmosphere is essential for the understanding of the defect-complexes behavior in these materials, as the iron doping rate increases, and a static magnetic field is applied.image