Suspended-core holey fiber for evanescent-field sensing

Abstract

Abstract.A simple fabrication technique for a silica suspended-core holey fiber design is presented that features a higher air-filling fraction than most holey fibers, making it ideal for evanescent-field-sensing applications. The holes in the fiber are defined through mechanical drilling of the preform, which is a significantly quicker and more straightforward approach to the customary stacking method. During the draw, the shape of the holes are manipulated so that the final fiber design approximates that of an air-suspended rod with three fine struts supporting the core. Modeling reveals that the modal overlap is greater than 29% at 1550 nm for a core diameter of 0.8 m, which is significantly higher than any previously reported index-guiding structure used for sensing. A basic gas sensor is demonstrated using acetylene as the sensing medium and the results are reported.

A comparative study of the fluorescence and photostability of common photoswitches in microstructured optical fibre

“…[41] The fibres have hole diameters of 27.7 μm, providing a total fill volume of 18 nL/cm. The core size is 1.5 μm.…”

Hollow-core photonic bandgap fibers: technology and applications

“…As the need for larger preform sizes emerges this may open up opportunities to try other approaches to preform manufacture such as sol-gel casting [12], mechanical drilling [13] or laser drilling [14]. Initial attempts have been made using these approaches in simpler microstructured fibres, but never on fibres with as complex a cross section as a HC-PBGF.…”

Optical Fibres for Distributed Corrosion Sensing - Architecture and Characterisation

“…For these fibres the PF overlaps with the voids, and by controlling the size of the core, this overlap between the light and the voids can be adjusted. If the voids of the fibre are then filled with liquids or gases this controllable interaction allows sensing measurements to be performed, using methods such as direct absorption [14] or various fluorescent techniques [8,15]. These suspended-core fibres dramatically improve fluorescence-based fibre sensors by making use of the increased PF provided by the micrometre scale core size and therefore increased sensor performance.…”

“…While suspended-core fibres have provided a highly sensitive sensing platform [8,14,[17][18][19][20], exploiting the significant fraction of guided power located within the holes, the closed structure makes it impossible to use them for distributed sensing applications. To overcome this, fabrication techniques that expose the core have been demonstrated by micro-machining fluidic side-channels at several locations along the fibre length [21][22][23][24], which results in short exposed regions in the order of tens of microns.…”

“…The silica exposed-core fibre preform, as shown in Figure 8(a), was fabricated by drilling three holes along the length of the fused silica rod, with centres spaced such that they form an equilateral triangle, and a slot was cut along the length of one of the holes. These methods expand on a combination of work previously shown by Webb et al [14] for fabricating silica suspended-core fibres by drilling the preform, and Warren-Smith et al [26] for cutting a thin slot into the side of the symmetric preform (soft glass) in order to expose the core region. The preform was cleaned after drilling using acetone and ultrapure (Milli-Q ™) water, then etched in a buffered hydrofluoric acid solution (BHF), made using 6 volumes of ammonium fluoride (NH 4 F, 40% solution) to 1 volume of hydrofluoric acid (HF, 50% solution), with a known etch rate of 100-250 nm/min [33].…”