Mathematical Modelling and Numerical Investigation of 2D Functional ZnO Photonic Sensor to Detect Urine Components

We have proposed a novel 2D zinc monoxide photonic sensor for detecting the components in urine samples. The proposed structure consists of linear waveguide and diamond-shaped 3 × 3 ZnO rods inside the ring resonator. To avoid a sharp bend of light at the corners of the linear waveguide region, the ZnO rods are shifted in the middle of the two rods for high transmission over a wide wavelength range and help to improve the characteristics parameters of the sensor. Further, we have evaluated the real part from the imaginary part of the refractive index using the Kramers–Kronig relationship for the different components of urine sample. The plane wave expansion (PWE) method is employed to calculate the band structure at the optimized rod radius and lattice constant. The finite-difference time-domain method is applied to observe the transmission characteristics and calculate the resonance wavelength. We have obtained an impressive sensitivity for the glucose concentration of 0.625 gm/dl, which is 28,820 nm/RIU. The highest quality factor and full-width at half maximum of 1663.52 and 1.002 nm, respectively, have been obtained for a glucose concentration of 15 gm/dl. The highest figure of merit and the lowest limit of detection are observed for the 2.5 gm/dl of urea concentration. To verify the linearity of the sensor, we have drawn fitted line for the glucose and urea concentration and obtained correlation coefficient of 0.944 and 0.998, respectively. Our calculated values of performance parameters found a considerable improvement over other existing structures, which shows the ability of the proposed sensor.