Integrated full vectorial FEM, FDTD and diffraction integrals in characterising visible light propagation through lossy biological media

In this thesis, the propagation characteristics of the biological optical waveguides, considering the materials as lossy in the optical frequencies, have been analysed. It has been found that the losses present in the biological materials in optical frequencies are not negligible, and the loss values have significant effects on the propagation characteristics of these waveguides. In biological optical waveguides, each waveguide is surrounded by parallel waveguides so that the propagation characteristics would be different from that of single waveguide present in a homogeneous material. In this thesis, the impacts of the presence of the neighbouring waveguides on the propagation characteristics of a waveguide are studied in details. Dispersion characteristics of the waveguides have been investigated, and the effects of the material loss, presence of the neighbouring waveguides and the presence of multi-layer W-fibre like structure on the dispersion characteristics have also been studied. The modal characteristics, the time-domain evolution of the signal and the diffraction characteristics have been integrated to explain some of the still unanswered questions in the visual systems. An attempt has been made to explain the Stiles-Crawford effect of human retina in light of the findings of this thesis. A full-vectorial H-field based finite element method (FEM) is used for the modal solutions, Finite Difference Time Domain (FDTD) is used to study the time evolution of the signals through the waveguides, and the Diffraction profiles have been obtained by Rayleigh-Sommerfeld(RS) diffraction integral.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

City, University of London

Year dc:date.issued

2015

Author dc:creator

• Rahman, M. E.

• RE Ophthalmology
• TA Engineering (General). Civil engineering (General)