Rapid long-period grating formation in hydrogen-loaded fibre with 157 nm F2-laser radiation

Role of hydrogen loading and glass composition on the defects generated by the femtosecond laser writing process of fiber Bragg gratings

“…For the Ge-doped SMF-28 fiber the UV results are less clear-cut. This is partly due to the fact that defect formation depends on the irradiation wavelength [19,20]. However, a FL band at 650 nm due to the formation of NBOHC defects has been established for a wide range of irradiation conditions [16].…”

Fabrication of strong long-period gratings in hydrogen-free fibers with 157-nm F_2-laser radiation

“…5 Comparison with 248-nm-exposed hydrogen-soaked f ibers also revealed a .250-fold enhancement of the 157-nm response. Such strong enhancement by hydrogen of F 2 -laser light is only apparent in LPFGs; only threefold enhancement of the 157-nm laser-induced refractive-index change was noted in hydrogen-soaked GeO 2 waveguides (3% GeO 2 ).…”

Investigation of long-period fibre gratings inscribed by high-intensity femtosecond UV laser light

“…Later, other methods of LPFG inscription, based on refractive index changes in the fibre core induced by thermal heating, were developed, however, in practice, the photochemical approach is most frequently employed for LPFG fabrication. Along with a standard singlequantum technique (248 or 244 nm irradiation), two other methods were proposed: vacuum UV (157 nm) irradiation [6,7], and femtosecond high-intensity 800 nm (or 400 nm) irradiation [8,9,10]. These newly developed photochemical methods include the excitation of high-energy electronic levels in Ge-doped fused silica due to vacuum UV single-quantum and IR (visible) multiple-photon techniques, respectively (see Fig.…”

“…1 the proposed approach together with the excitation pathways for other photochemical techniques are depicted. Due to the high excitation energy this approach is expected to bring a rather high efficiency (quantum yield) of refractive index change in the fibre core, comparable with the action of vacuum UV light [6,7]. The first experiments [13,14] demonstrated the successful inscription of long-period gratings in some telecom fibres by high-intensity femtosecond UV pulses; however, neither the optimisation of irradiation conditions, nor the detailed thermal studies of LPFGs were performed.…”