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

Abstract

kW fiber lasers, long-term optical data storage such as Microsoft's "project silica", [1] etc.) and optical sensing (structural health monitoring of engines, deep drilling). [2] In most applications operating in a HT environment, refractory crystalline oxide materials such as alumina (Al 2 O 3 ) or zirconia (ZrO 2 ) are candidates of choice, due to their high melting points and good resistance to oxidation and abrasion. Furthermore, directionally solidified eutectic ceramics (e.g., unidirectionally solidified Al 2 O 3 /oxide eutectic composite made of perovskite or garnet phase) also can improve thermal stability, [3] as demonstrated for instance in aircraft gas turbines and thermal power generation systems (e.g., operation for 1000 h at 1700 °C).However, other HT applications, such as long-lived data storage for the zettabyte era [1] or optical sensors (down-hole oil/gas exploration, monitoring of structure health, temperature regulation of engines, etc.) require using glass materials that can be functionalized and shaped into chips, disks, planar waveguides or optical fibers. Both the materials and geometric designs need be considered due to practical demands, such as compactness and lightness, flexibility, high-transparency, fast and complex manufacturing shaping, chemical/radioactive/ electromagnetic resistance, and low cost. For these reasons, 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 (Al 2 O 3 ) 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 GeO 2doped 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.

Optical Waveguides Fabricated via Femtosecond Direct Laser Writing: Processes, Materials, and Devices

“…Reproduced under the terms of the CC‐BY‐NC license. [ 181 ] Copyright 2022, The Authors, published by Wiley–VCH GmbH. e) Microscope images of the cross‐section of the straight waveguide, 1 × 2, 1 × 4 beam splitters.…”

“…Wang et al. [ 181 ] proposed sapphire (Figure 9c) and yttrium aluminum garnet (Figure 9d) derived all‐glass silicate optical fibers, which exhibit improved thermal stability compared to commercial pure silica and GeO 2 ‐doped silica analogs. The optical properties of the derived fibers will decrease significantly when the temperature exceeds 800 °C, much higher than 200 °C of commercial fibers.…”

“…c) SEM image of sapphire-derived fiber written by Fs-laser. Reproduced under the terms of the CC-BY-NC license [181]. Copyright 2022, The Authors, published by Wiley-VCH GmbH.…”

Nanoscale investigations of femtosecond laser induced nanogratings in optical glasses

“…The focus of this work is on NGs, which have found use in various elds and applications such as health, 5 optical data storage, [6][7][8] optouidics, 9,10 sensors in harsh environments 11,12 and a wide range of optical components like 3D optical waveguides, 3D geometric phase optics, 13 and polarizing optical devices. 14,15 Porous NGs and related strong birefringence are a spectacular manifestation of a light controlled glass decomposition, and have been primarily reported in pure silica 16 and slightly doped silica glasses.…”

Theoretical and experimental investigation of Al3+ ion-suppressed phase-separation structures in rare-earth-doped high-phosphorus silica glasses

“…As the core gain medium of fiber lasers, rare-earth (RE)-doped silica-based glasses play an important role in improving the conversion efficiency and output power. [1][2][3][4][5][6] Currently, to reduce the influence of the fluorescence quenching effect, mainstream RE-doped silica-based glasses usually introduce low levels of codopants (e.g. Al, Al-P, F, etc.)…”