Transmittance Spectrum Analysis of a (SiO₂/TiO₂) One-dimensional Defective Photonic Crystal Structure for some Human Blood Compound Sensing

Abstract

This study aims to investigate the transmittance spectrum of a one-dimensional photonic crystal 1D-PhC biosensor composed of SiO₂/TiO₂ multilayers for real-time detection of human blood components in the visible wavelength range. The Transfer Matrix Method TMM implemented in Python was employed to derive the transmittance spectrum of the sensor. The proposed sensor effectively detects shifts in the transmittance profile of four selected blood compound indices (blood plasma, white blood cells, hemoglobin, and red blood cells) within the photonic band gap (PBG) of wavelength between 650 – 1050 nm and 2170 nm thickness of the defect layer using seven periodic layers of TiO₂/SiO₂ and a 20° incident theta angle. A parametric analysis was conducted by varying the defect layer thickness d₀, the number of periodic layers N, and the incidence angle θ_i to optimize the sensor performance. At d₀ = 10D and N = 7, the optimized sensor design consistently detected subtle changes in the refractive index caused by hemoglobin level fluctuations, maintaining high sensitivity and quality factors across various concentrations.