Thesis (Ph.D.) - Cairo University - Faculty of National Institute of Laser Enhanced Sciences - Department of Engineering Application of Laser

Nowadays, developing photonic biosensors with high sensitivity and compact size becomes mandatory due to the rapid progress in medical diagnostics. In this context, plasmonic photonic crystal fiber (PCF) sensors have advantages in terms of biocompatible and real time bio-sensing thanks to their high flexibility and unusual light control mechanisms. This thesis focuses on the design and analysis of highly sensitive, compact size, biocompatible and multifunctional PCF biosensors. The modal analysis of the proposed sensors is made by full-vectorial finite-element method with perfect matched layer boundary condition. First, dual core (DC) PCF multi-functional biosensor is also proposed and analyzed. The suggested structure has a dual-core filled with alcohol mixture. Further, two gold rods are mounted in the inner surface of central analyte infiltrated hole. The numerical results show that the two fundamental core modes (even mode and odd mode) have different characteristics through the entire wavelength range due to the geometry of the proposed PCF infiltrated by the alcohol. Moreover, the suggested design has very high refractive index (RI) and temperature sensitivity of 34600 nm/RIU and 21.05 nm/{u00B0}C, respectively, with high resolution of 2.89{u00D7}{u3016}10{u3017}^(-6) RIU. The achieved sensitivity is superior to those in the literature with muli-functionality. A highly sensitive dual D-shaped PCF biosensor based on surface plasmon resonance (SPR) sensing mechanism is proposed and analyzed. The upper and lower surfaces of the PCF are etched where two gold nanorods are mounted on them. At the resonance wavelength, the effective indices of the core guided mode and surface plasmon mode are equal. Therefore, maximum power transfer occurs from the core mode to the surface plasmon mode with high losses. The resonance wavelength highly depends on the analyte refractive index. Consequently, the suggested biosensor has high refractive index (RI) sensitivity of 12800 nm/RIU with resolution of 7.8{u00D7}{u3016}10{u3017}^(-6) RIU. Next, a multifunctional PCF is reported that can operate as a RI sensor and polarization filter as well. The full vectorial finite element method (FV-FEM) is used to numerically analyze the proposed design. Further, the filter characteristics are approved by using finite difference time domain method (FDTD). The suggested PCF filter has a dual D-shaped PCF. Thegold layers are coated over the etched surfaces. Therefore, the TM mode is attenuated due to the coupling with the plasmonic modes. A wide operation bandwidth from n=1.1 æm to n=1.7 æm with crosstalk (CT) less than -21 dB and very short device length of 36 æm are achieved.The attenuation loss peak of the TM mode at the resonance frequency depends on the analyte refractive index which achieves the RI sensing 5300 nm/RIU with resolution of 1.887{u00D7}{u3016}10{u3017}^(-5) RIU.

Issued also as CD