26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Femtosecond-Laser Engineering of Glasses and Optical Fibres for High-Temperature Sensing

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Invited talk ANZOS | Optical Materials and Fabrication (ANZCOP OMFAB)

Description

Optical fibres are attractive sensing platforms for harsh environments, but their ultimate operating temperature is set by the stability of both the glass and the laser-written structure. Femtosecond laser direct writing offers a unique route to locally engineer the refractive index and microstructure of optical glasses and fibres, enabling compact photonic devices and fibre sensors for harsh environments. Among the laser-induced modifications, porous nanogratings (Type II) are particularly attractive because of their strong birefringence and remarkable thermal stability, and can be exploited in femtosecond-written fibre Bragg gratings for sensing at elevated temperatures (typ.>800°C).

This talk will examine how far such laser-written functions can be pushed toward extreme-temperature operation. Building on a comparative study of more than 30 optical glasses and fibres, we will discuss the respective roles of laser parameters, nanostructure morphology and, especially, glass composition. For conventional Type II structures, thermal erasure is largely governed by the temperature-dependent viscosity of the host glass and can be rationalized through the evolution of laser-induced nanopores. However, several refractory compositions depart strongly from this simple picture.

In particular, Al-rich aluminosilicate glasses can retain a useful refractive-index contrast above 1400 °C, associated with laser-induced phase separation, nanocrystallization and chemical migration. More recent results extend this materials approach to non-conventional oxycarbide glasses. SiOC already exceeds high-purity silica in thermal stability while preserving a Type-II-like optical response, whereas SiAlOC shows strong birefringence and enhanced resistance to thermal erasure, opening questions about the nature and stabilization of the laser-written nanophase.

These results illustrate how combining femtosecond laser processing with composition-engineered, fibre-compatible glasses may provide a route beyond the intrinsic thermal limits of conventional silica for high-temperature photonic sensing.