High Sensibility Optical Water Sensor Using a One-Dimensional Defective Photonic Crystal

• Published in: Optical memory & neural networks 2021-10, Vol.30 (4), p.298-311
• Main Authors: Youssef Ben-Ali, El Kadmiri, Ilyass, Falyouni, Farid, Essahlaoui, Abdelouahed, Bria, Driss
• Format: Article
• Language: English
• Subjects: Complexity; Computer Science; Information Storage and Retrieval
• ISSN: 1060-992X; 1934-7898
• DOI: 10.3103/S1060992X21040032

In recent years, there has been more research on the use of defective photonic crystals (PCs) in the field of detection. The application of these PCs as liquid sensors seems very promising, because of their miniaturization and high spectral sensitivities. This work aims to study theoretically the effect of the refractive index of polluted water on the transmission spectrum of a one-dimensional photonic crystal (PC), made of alternating layers of silicon dioxide and titanium dioxide and containing two defect layers of common heavy oil. These two defect layers will be filled with polluted water. The insertion of two polluted water layers of thickness 360 nm inside the structure, creates two very narrow defect modes in the gaps with a high-quality factor Q ( Q = 707) and a maximum transmittance ( 100%) in the wavelength infrared interval belonging to (1090–1115 nm). The modes falling inside the band gaps are very sensitive to the thicknesses of the defects and the refractive indexes of the polluted water. They shift to higher wavelengths when the refractive indexes of defects increases. A detection limit 7 × 10 –3 refractive index units has been derived from measurements with a sensitivity of 405 nm per refractive index unit. Therefore, our proposed structure is a good candidate for the refractive index water sensor design which has great application prospects in optical, medical, and biological sensing.