Sub-wavelength thick ITO-incorporated PCF based biosensor for non-invasive sensing of glucose and urea

Abstract

This study presents an ultrathin indium tin oxide coated photonic crystal fiber (PCF) incorporated biosensor, suitable for sensing glucose and urea from in-vitro samples. The proposed device detects analytes with refractive indices spanning from 1.32 to 1.36 with maximum amplitude sensitivity of 231 RIU-1. A peak wavelength sensing capability of 12,000 nm/RIU at near-infrared spectrum (1400–2000nm) has also been achieved. Our design incorporates miniature air holes in the PCF to excite core-guided mode and one-tenth of the operating wavelength thick indium tin oxide (ITO) based cladding as the adaptive plasmonic surface. Air gaps in an “X” pattern, etched along the cross-sectional plane of the PCF, enhance the phase coherence between the plasmonic and the core-guided mode for Y polarized light for a narrow spectrum, ensuring higher Q-factor and hence greater sensitivity. The design is characterized using finite element method (FEM) with sensor resolutions as high as 8.33 × 10−6 RIU.