TY  - JOUR
AU  - Shchur, Yaroslav
AU  - Karout, Houda El
AU  - Sahraoui, Bouchta
AU  - Andrushchak, Anatoliy
AU  - Beltramo, Guillermo
AU  - Pustovyi, Denys
AU  - Vitusevich, Svetlana
AU  - Huber, Patrick
AU  - Kityk, Andriy V.
TI  - Synthesis, nanocrystalline morphology, lattice dynamics and nonlinear optics of mesoporous
JO  - Scientific reports
VL  - 14
IS  - 1
SN  - 2045-2322
CY  - [London]
PB  - Macmillan Publishers Limited, part of Springer Nature
M1  - PUBDB-2024-06361
SP  - 24237
PY  - 2024
AB  - We demonstrate a hybrid nanocomposite combining mesoporous silica, pSiO<sub>2</sub>, as a host medium and guest lithium niobate LiNbO<sub>3</sub> nanocrystals embedded into tubular silica nanochannels by calcination of the precursor mixed solution of lithium and niobium salts. High-resolution transmission electron microscopy, X-ray diffraction and Raman scattering techniques reveal trigonal LiNbO3 nanocrystals within the pSiO<sub>2</sub> nanochannels, indicating their random texture morphology. Annealing at high temperatures ( 950◦C) during calcination also leads to partial crystallization of the pSiO<sub>2</sub> matrix with the formation of trigonal α-SiO<sub>2</sub> nanocrystals. The Raman microscopy analysis of the pSiO<sub>2</sub>:LiNbO<sub>3</sub> nanocomposite reveals three structural crystalline phases, α − SiO<sub>2</sub>, LiNbO<sub>3</sub> and a mixed phase which involves the α-SiO<sub>2</sub> phase of host membrane and LiNbO<sub>3</sub> nanocrystals embedded into the membrane. The finite size of the LiNbO<sub>3</sub> nanocrystals results in specific features of the LO-TO phonon frequency splitting, which are investigated by Raman microscopy. In the transmission geometry, the second harmonic generation emission exhibits no Maker fringes and is characterized by a broad angular diagram of diffusely scattered light. The second harmonic generation response is independent of the polarization direction of the incident pump light, thus indicating a spatial isotropy of the nonlinear optical conversion in the pSiO<sub>2</sub>:LiNbO<sub>3</sub> composite, consistent with the randomly oriented textural morphology of the deposited LiNbO<sub>3</sub> nanocrystals. The contribution of the guest LiNbO<sub>3</sub> nanocrystals to the second harmonic generation effect was found to be strongly dominant compared to the partially crystallized host pSiO<sub>2</sub> matrix. The nanocomposite pSiO<sub>2</sub>:LiNbO<sub>3</sub> membrane, set in the 90◦ nonlinearoptical geometry, shows unusually high diffusely transmitted second harmonic generation light (back-reflected emission), apparently supported by internal light reflection from the tubular nanochannel network. Despite the fundamental interest, the revealed anomalous back-reflected second harmonic generation emission from pSiO<sub>2</sub>:LiNbO<sub>3</sub> nanocomposite membranes expands the prospects for their photonic and nonlinear optical applications.   
LB  - PUB:(DE-HGF)16
C6  - 39414882
UR  - <Go to ISI:>//WOS:001336670300020
DO  - DOI:10.1038/s41598-024-75686-6
UR  - https://bib-pubdb1.desy.de/record/616201
ER  -