Ageing of PVP/LiNbO3 solutions and its impact on the optical properties of Er3+/Yb3+:LiNbO3 waveguiding films

• Published in: The Journal of physics and chemistry of solids 2017-12, Vol.111, p.343-348
• Main Authors: Rubešová, K., Mikolášová, D., Hlásek, T., Jakeš, V., Nekvindová, P., Matějka, P., Dendisová, M., Cílová, Z. Zlámalová, Oswald, J.
• Format: Article
• Language: English
• Subjects: Ageing; Lithium niobate; Polyvinylpyrrolidone; Sol-gel; Waveguide
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2017.08.016

This study extends our previous work that describes the sol-gel preparation of Er3+/Yb3+:LiNbO3 waveguiding films. Here we describe the influence of the starting PVP/2-methoxyethanol solutions ageing on the properties of films deposited by spin-coating. We tested solutions prepared from PVP of two molecular masses (29,000 g/mol and 360,000 g/mol) aged for up to 10 months. To establish the Er3+/Yb3+:LiNbO3 film quality, we used XRD measurement, photoluminescence spectroscopy and m-line spectroscopy. We found out that even aged solutions (prepared by this non-hydrolytic method) can be used for reproducible deposition of thin films; however, the heat treatment of deposited layers must be modified. The change in the thermal behaviour of solutions in the course of ageing is demonstrated by TG-DTA measurement. The intramolecular interactions in the PVP/2-methoxyethanol system and their change after ageing are described using mid-IR spectroscopy. Our results demonstrate that the PVP solution aged for months can be used for the successful preparation of waveguiding oxide film but special attention must be paid to the heat treatment regime used after films deposition. •PVP-solutions freshly prepared or aged (up to 10 month) were spin-coated on Al2O3.•Use of aged solutions in a non-hydrolytic method not deteriorating film microstructure.•If proper thermal treatment used, waveguiding Er3+/Yb3+:LiNbO3 films were prepared.•Process of ageing and its influence on thermal behaviour explained by IR spectra.•Change in the nature of non-bonding interactions causes change in thermal behaviour.