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 μm in length located at the fiber tip of 3 μm 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 by metal-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.