Highly Sensitive D-Shaped Photonic Crystal Fiber-Based Plasmonic Biosensor in Visible to Near-IR

A simple D-shaped photonic crystal fiber (PCF)based surface plasmon resonance (SPR) biosensor is proposed for refractive index sensing in visible to near infrared (IR) region. A thin Titanium di-oxide (TiO ₂ ) layer is used as an adhesive layer to strongly attach the plasmonic gold (Au) layer with silica fiber surface. TiO ₂ also helps to tune the operating sensor wavelength from visible to near IR (550-1770-nm wavelength). Finite-element method has been used to investigate the guiding properties. The proposed sensor shows the maximum wavelength interrogation sensitivity of 46 000 nm/RIU and the average sensitivity of 9,800 nm/RIU in the sensing range of 1.33-1.43. It also shows the maximum amplitude sensitivity of 1,086 RIU ^-1 . Using the wavelength and amplitude interrogation methods, proposed sensor gives the theoretical maximum resolution of 2.2 × 10 ^-6 and 9.2 ×10 ^-6 RIU, respectively. To the best of our knowledge, it has the highest sensitivity and sensor resolution among the reported PCF SPR sensors. The proposed D-shaped PCF has been fabricated following the standard stack-and-draw method to show the feasibility of the proposed sensor. Due to the promising results over the broad range of analyte RI, it would be an excellent candidate for the detection of biomolecules, organic chemicals, chemical, and other analytes.