Femtosecond laser machining of hollow-core negative curvature fibres

Abstract

Hollow core negative curvature fibres (NCFs) are a relatively new class of microstructured optical fibre with potential applications in areas such as the delivery of high power laser light and gas sensing. For sensing, it is necessary for the measurand to interact with the guided mode. To facilitate this, a novel femtosecond laser-based machining protocol has been developed that allows the precision sculpting of access slots into the NCF core along the length of the fibre. The process is a direct-write process using a digitally defined scanning strategy with no need for physical masks or additional processing such as wet etchants and/or focussed ion beam machining. Due to the inherent flexibility of the machining strategy and the high level of control over the depth of material removal, it is likely that this new technique will be transferable to a wide range of microstructured fibres.

Fabrication of Microchannels in a Nodeless Antiresonant Hollow-Core Fiber Using Femtosecond Laser Pulses

“…The methods of microchannel realization using an fs laser presented in the literature so far have introduced relatively high losses at the level of 0.45 dB per hole [20], and more. The lowest loss of 0.35 dB per hole was recorded for a single microchannel made in an HCF assisted by liquid [17].…”

Optofluidic channels in anti-resonant hollow-core fibers using focused ion beam

“…Femtosecond laser ablation technology has been used to drill microchannel in ARHCF, inducing a relatively high loss of ~1 dB per channel 25 due to damages to the capillaries. A very recent study has used femtosecond laser micromachining of smooth channels in ARHCFs to access the core of the fiber, achieving a big channel size of 150 µm with an induced loss of 0.45 dB 26 . This is still higher than the 0.35 dB loss reported in 4 although with a much larger hole size.…”