Miniaturized Metal-Dielectric-Hybrid Fiber Tip Grating for Refractive Index Sensing

We fabricate a miniaturized metal-dielectric-hybrid fiber tip grating (FTG) using a focused ion beam (FIB) method with high accuracy for refractive index sensing applications. It is the smallest fiber grating by now (nearly 10 m in length located at the fiber tip of 3 m in radius) and it has strong surface corrugations with notches periodically. The grating shows refractive index sensitive [125 nm/refractive index unit (RIU)] and insensitive (nearly zero) properties for reflection channels of different resonant modes bymetal-dielectric cladding structure. It can be used as a multichannel sensor for simultaneous refractive index and temperature/pressure measurements. Taking advantage of its flexible design, tiny size, unique modal and spectral characteristics, the metal-dielectric-hybrid FTG has great potential in fast-response detection of ultrasmall objects.