Compact microfiber Bragg gratings with high-index contrast

Abstract

We fabricate fiber Bragg grating (FBG) in microfibers (MFs) using focused ion beam milling technique. By periodically etching $100\mathrm{nm}$-depth grooves on the surface of silica MFs with diameters less than $2\mathrm{\mu m}$, evident grating features with transmission dip up to $15\mathrm{dB}$ are obtained. Because of the high-index contrast of the gratings structure, the length of the microfiber Bragg grating (MFBG) can be reduced to $500\mathrm{\mu m}$ level. Using a $518\mathrm{\mu m}$-length $1.8\mathrm{\mu m}$-diameter MFBG, we also demonstrate sensitivity up to $660\mathrm{nm}$ per refractive index unit (RIU) for refractive index (RI) sensing. The highly compact MFBGs demonstrated here may serve as low-dimensional building blocks for miniaturized photonic components and devices.

© 2011 Optical Society of America

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