Enhanced sensitivity of fiber optic evanescent wave absorption-based concentration sensor by shining a Bessel–Gauss beam and effect of fiber bending on the sensor response: a theoretical analysis

Abstract

We present a theoretical perspective on the notion of a highly sensitive multimode fiber optic evanescent wave absorption-based sensor by exploiting a zero-order Bessel–Gauss beam to determine the concentration of sodium chloride (NaCl) from its aqueous solution. The phenomenon of excited waveguide modes inside the sensor structure has been assessed by using a classical wave-optic model. By harnessing the advantages of the Bessel–Gauss beam, the difference in transmitted output power is evaluated for various concentrations of NaCl, ranging from 0 to 360 g/L. To corroborate our theoretical predictions, the computer-aided simulation in Mode Solutions software has been performed on the proposed sensing configuration. In contrast to the conventional concentration sensor using Gaussian beam, the projected scheme yields a maximum 14.40-fold superior sensitivity of 0.072 dB / gL − 1 with a commendable sensing resolution of ∼0.013 g / L. Also, attention has been paid to the Bessel–Gauss beam shined U-bent fiber-optic absorption-based concentration sensor, where the sensor response has been numerically investigated for different bending radii, and it is concluded that the sensitivity can be enhanced appreciably by gently reducing the bending radius. Due to ultrahigh sensitivity, the present paradigm is very much alluring and evocative, establishing pivotal implication in chemical and biological sensing fields.