Abstract
Embedding strong photonic stopbands into traditional optical fibre that can directly access and sense the outside environment is challenging, relying on tedious nano-processing steps that result in fragile thinned fibre. Ultrashort-pulsed laser filaments have recently provided a non-contact means of opening high-aspect ratio nano-holes inside of bulk transparent glasses. This method has been extended here to optical fibre, resulting in high density arrays of laser filamented holes penetrating transversely through the silica cladding and guiding core to provide high refractive index contrast Bragg gratings in the telecommunication band. The point‐by‐point fabrication was combined with post-chemical etching to engineer strong photonic stopbands directly inside of the compact and flexible fibre. Fibre Bragg gratings with sharply resolved π-shifts are presented for high resolution refractive index sensing from {n}_{{{{{{rm{H}}}}}}} = 1 to 1.67 as the nano-holes were readily wetted and filled with various solvents and oils through an intact fibre cladding.
Highlights
Embedding strong photonic stopbands into traditional optical fibre that can directly access and sense the outside environment is challenging, relying on tedious nano-processing steps that result in fragile thinned fibre
Laser, and mechanical machining or thinning of the cladding have facilitated evanescent sensing at the surface of the FBG14,29–31
Fibre Bragg gratings (FBG) with strong resonances and sharply resolved π-shifts are presented that provided high capillarity for wetting with various solvents and oils, demonstrating high-resolution refractive index (RI) sensing from nH = 1–1.67 through an intact fibre cladding
Summary
Embedding strong photonic stopbands into traditional optical fibre that can directly access and sense the outside environment is challenging, relying on tedious nano-processing steps that result in fragile thinned fibre. The validation of strong and responsive photonic stopbands is presented in the reflection spectra of Fig. 4a for nanohole arrays filled with air and a range of solvents (Table 1).
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