Local tuning of fused silica thermal expansion coefficient using femtosecond laser

Femtosecond laser exposure of fused silica in the nonablative regime can lead to various localized bulk modifications of the material structure. In this paper, we show that these laser-induced modifications can be used to tune silica thermal expansion properties permanently. In particular, we demonstrate that a given exposer regime leads to lower thermal expansion than the bulk, while other exposure conditions yield the opposite results. This remarkable property enables the possibility to engineer a given thermal expansion behavior by selectively exposing a material volume to a femtosecond laser beam. This finding opens up opportunities for a variety of integrated precision instruments and optical devices for which inertness to thermal fluctuations is essential.