3D Laser Engineering of Molten Core Optical Fibers: Toward a New Generation of Harsh Environment Sensing Devices

Aluminosilicate glasses offer wide-ranging potential as enabling materials for a new generation of optical devices operating in harsh environments. In this work, a nonconventional manufacturing process, the molten core method, is employed to fabricate and study sapphire (Al2O3) and YAG (yttrium aluminum garnet) derived all-glass silicate optical fibers in which a femtosecond (fs) laser is used to imprint oriented nanostructures inside the fiber cores. Both writing kinetics and thermal stability of the laser-modified regions are investigated over a wide temperature range (20–1200 °C). The laser-imprinted modifications in these high alumina-content fibers exhibit improved thermal stability with respect to commercial pure silica and GeO2-doped silica analogs. Furthermore, optical devices in the form of Rayleigh backscattering and fiber Bragg grating sensors are fabricated to demonstrate the high-temperature sensitivity and stability of these nonconventional fibers. This functionalization of aluminosilicate fibers by fs-laser direct writing opens the door to a new generation of optical devices suitable for high-temperature operation.