An investigation of novel materials for active optical devices

Jander, Peter (2003) An investigation of novel materials for active optical devices. University of Southampton, Department of Electronics and Computer Science, Doctoral Thesis, 153pp.

Record type: Thesis (Doctoral)

Abstract

The potential of a number of doped materials as amplifiers for optical communication has been assessed. This work focuses on transparent glass-ceramics as novel hybrid materials of glasses and crystals.

Glass-ceramics comprising of LaF₃ crystals in an aluminosilicate glass matrix, doped with Er³⁺, Pr³⁺ and Tm³⁺ have been prepared and characterized. Spectroscopy of these glass-ceramics is focused on the distribution of the dopant ions between the crystals and the residual glass. A novel method to calculate the ion distribution, based on fluorescence lifetime measurements, is developed and applied to both Er³⁺ and Pr³⁺ doped glass-ceramics. In the case of Er³⁺, less than 5% of the ions segregate into the crystals. In contrast to that, up to 50% of the Pr³⁺ ions are found in the crystals. It is shown that virtually complete segregation of the Pr³⁺ ions into the crystals is necessary for efficient amplifier operation.

Glasses in the yttria-alumina-silica system are prepared and characterized with a view both as a host material for rare earth and transition metal ions, and as a precursor glass for transparent glass-ceramics with YAG nanocrystals. Subsolidus crystallisation studies identify a glass composition promising for YAG glass-ceramics, but also highlight the problem of surface crystallisation.

Thulium doped YAS glass is identified as a potential gain medium for a S-band amplifier, because the fluorescence band at 1.47µm has a width of 125nm with an estimated quantum efficiency of 20%. Spectroscopy on Er³⁺-doped YAS glass shows that the glass can accommodate 26000ppm Er³⁺ without clustering.

The prospect of a Cr⁴⁺:YAG glass-ceramic fibre amplifier is discussed.