Plasmonic Refractive Index Sensor Employing Niobium Nanofilm on Photonic Crystal Fiber

This letter presents a numerical investigation of a highly sensitive refractive index sensor based on surface plasmon resonance. An ultrathin niobium nanofilm is proposed as a new plasmonic material, which outperforms existing plasmonic materials. This nanofilm is employed on a photonic crystal fiber for the first time resulting sensing over a wide range of refractive indices. Finite-element method-based numerical analysis shows that maximum amplitude sensitivity of 1560 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and wavelength sensitivity of 8000 nm/RIU can be obtained for an analyte index of 1.40. A thin aluminum oxide (Al2O3) film is deposited on the outer layer of niobium film to enhance the coupling strength and in order to tune the resonance wavelength. Moreover, the effects of varying thickness…