Hypercholesterolemia diagnosis by a biosensor based on photonic crystal PANDA structure

A biosensor based on 2-D photonic crystals is presented and considered. The proposed structure is made of 24 × 23 Si rods in the air background. The presented biosensor would be considered for detection of Cholesterol concentrations in blood samples, which can aid physicians in diagnosis of Hypercholesterolemia and heart diseases in early stages. To facilitate the designation and fabrication processes and overcome the gain and nonlinearity problems, only linear rods would be utilized. The presented structure operates based on the interference and scattering effects of Si defect rods positioned in the structure (black rods operate as the confining sensing media and dark green rods function as the coupling rods). The PANDA (the proposed structure indicates a PANDA face)-shaped waveguides can filter the resonant wavelengths. For studying the functionality of the proposed biosensor, photonic band gap (by the plane wave expansion (PWE) method) and field distribution (by the finite-difference-time-domain (FDTD) method) spectra should be considered. The appropriate dimension of the proposed biosensor (111.78 μm²) makes it a considerable option for utilization in bio-optical integrated circuits. Finally, for the Cholesterol concentrations in blood samples, the remarkable sensitivity (595.74 nm/RIU “RIU stands for refractive index unit”), quality factor (35–46), detection limit (6.1e−3–6.7e−3) RIU and figure of merit (14.89–16.3) RIU⁻¹ were achieved.