Point-by-point written fiber-Bragg gratings and their application in complex grating designs

TLDR

The point‑by‑point technique of fabricating fibre‑Bragg gratings with an ultrafast laser gives complete control over the position of each index modification, enabling tailoring of local phase, amplitude and spacing to produce gratings with complex transmission and reflection spectra. We report a series of grating structures realized by exploiting these flexibilities. A coupled‑mode theory model provides important insights into the manufacture of such gratings. The reported structures include controlled‑bandwidth, amplitude‑ and phase‑modulated sampled (or superstructured) gratings, demonstrating a quick and easy method for producing complex, non‑uniform grating structures in fibres and other mono‑mode waveguiding structures.

Abstract

The point-by-point technique of fabricating fibre-Bragg gratings using an ultrafast laser enables complete control of the position of each index modification that comprises the grating. By tailoring the local phase, amplitude and spacing of the grating's refractive index modulations it is possible to create gratings with complex transmission and reflection spectra. We report a series of grating structures that were realized by exploiting these flexibilities. Such structures include gratings with controlled bandwidth, and amplitude- and phase-modulated sampled (or superstructured) gratings. A model based on coupled-mode theory provides important insights into the manufacture of such gratings. Our approach offers a quick and easy method of producing complex, non-uniform grating structures in both fibres and other mono-mode waveguiding structures.