Sensitivity enhancement of an optical sensor based on a binary photonic crystal for the detection of Escherichia coli by controlling the central wavelength and the angle of incidence

Sofyan A Taya,Shobhit K Patel,Ilhami Colak,Dana N Alhamss

doi:10.1007/s11082-022-03511-3

Abstract

A one-dimensional binary photonic crystal with the structure air/(GaAs,SiO2)N/D/(GaAs,SiO2)N/glass is proposed as an optical sensor to detect E. coli bacteria, where D is the defect layer. Water and E. coli bacteria are treated as the defect layer. The sensing mechanism of the proposed detector is based on the refractive index difference between pure water and waterborne bacteria samples. The transmission spectra of the photonic crystal are investigated and the sensitivity to E. coli bacteria is calculated. The effects of the central wavelength and the angle of incidence on the sensitivity and sensor performance parameters are studied. It is found that the central wavelength increase can enhance the sensor sensitivity and most of the performance parameters. Increasing the incidence angle can improve the sensitivity and all the performance parameters such as full width at half maximum, quality factor, detection limit, sensor resolution, signal-to-noise ratio, dynamic range, detection accuracy and figure of merit. The sensitivity, quality factor and detection limit that have been obtained are 213.259 nm/RIU, 10,010 and 0.0318, respectively.

Highlights

Varying types of bacteria have different water body contamination levels
The thicknesses of GaAs and SiO2 layers are selected based on Bragg quarter-wave conditions such as di = 4λnci, where λc is the central wavelength
The thickness of the defect layer is taken as dD = dGaAs + dSiO2

Summary

Introduction

Varying types of bacteria have different water body contamination levels. The presence detection of bacteria in water, plays a significant role in ensuring drinking water in a safe manner. Escherichia coli (E. coli) is a prokaryotic bacterium which in humans and other animals is known to cause diarrhea This is a key bacterial indicator for environmental monitoring of water quality and food security [1]. The most common existing detection techniques of E. coli bacteria are protein-chip technology [2], polymerase chain reaction [3], nucleic acid hybridization [4], immunology [5] and isolation and culture [6]. These results are exact, certain restrictions still remain, such as complicated operation and extended analysis time. Due to the vast range of applications in optics, optoelectronics and chemical and biological sensing, photonic crystals (PCs) have become very attractive in both technology and science [10-

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