Mikko Hongisto’s research focused on developing fundamental understanding of structure-property relationships in ytterbium-doped glasses. In his research, new oxyfluorophosphate glass compositions were characterized, and transparent glass-ceramics were obtained through controlled heat treatments. Also, compositional effects on crystallization behaviour and emission spectra were examined.
To address instability issues, Hongisto incorporated network-forming oxides like aluminium oxide, titanium oxide, and zinc oxide to investigate their impact on water absorption over time. Results showed these oxides can strengthen connectivity and modify properties while maintaining emission performance.
In addition, Hongisto subjected different glass families doped with ytterbium to radiation treatments to evaluate defect formation and recovery capacity.
“Phosphate and borosilicate glasses exhibited the highest initial radiation sensitivity but greater self-recovery potential with heat treatment. Tellurite glasses showed remarkably low defect creation during irradiation, highlighting opportunities for radiation resistant materials,” he explains.
Ytterbium-doped borosilicate glass fibres with round and rectangular geometries were also evaluated for stability in solution. Findings elucidated the influence of fibre design on degradation kinetics, emphasizing geometry’s role in controlling resorption behaviour for biomedical applications.
“My work advances fundamental understanding of manipulating ytterbium-doped glass performance through modifications,” says Hongisto.
The insights support optimization of glass-based materials with applications in photonics, healthcare and beyond.
Public defence on Thursday 29 February
The doctoral dissertation of Mikko Hongisto in the field physics titled "Development of ytterbium-doped optical glasses and glass-ceramics and their response to various treatments" will be publicly examined at the Faculty of Engineering and Natural Sciences of Tampere University at 12:00 on 29 February 2024 at Hervanta Campus in auditorium S2 (SA203) of the Sähkötalo building (Korkeakoulunkatu 3, Tampere).
The Opponent will be Professor Laurent Calvez from University of Rennes. The Custos will be Professor Laeticia Petit from Tampere University, Finland.
The doctoral dissertation is available online.
The public defence can be followed via remote connection (link to be added).