| Tissue optics has been traditionally studied using heuristic approximations, mainly due to extreme complexity involved. Regardless of the popularity of such approximation schemes, the validity of such approximation schemes and their applicable regimes remain yet to be determined.; The finite-difference time-domain (FDTD) is a numerical method based on fundamental electromagnetic principles. However, due to its intense computational requirements, it is impractical to simulate more than a few cells in 3-D with current available computer resources.; Based on the new pseudo-spectral time-domain (PSTD) algorithm proposed by Q. H. Liu in 1997, combined with parallel computing technology, it is now possible to model an aggregate of hundreds of cells in 3-D, or even thousands of cells in 2-D.; The development of the PSTD suite has been completed and employed in various research projects. The total scattering cross-section (TSCS) of random media consisting of closely packed scatterers has been rigorously analyzed. Specific results indicate that the TSCS is determined by the global geometry and averaged refractive index. Furthermore, the noise-like high-frequency oscillation of the TSCS is analyzed. Lastly, a correlation relationship of the TSCS and the individual constituent scatterers is identified, revealing possibilities of obtaining microscopic geometrical details from macroscopic scattered light. Together, research findings suggest that, optical properties of closely packed random media are primarily determined by the overall geometry as a whole, rather than a sum of consecutive series of independent scattering events.; The coherent backscattering (CBS) phenomenon is directly simulated. With a frequency-averaging method, the speckle effect is dramatically reduced, revealing a clear CBS peak with excellent agreement with the CBS theory. Specific results represent, to the best of the author's knowledge, the first direct simulation of the CBS peak from numerical experiments by rigorously solving Maxwell's equations, without employing indirect transformations or heuristic approximations.; In summary, novel simulation results of tissue optics have been reported in this dissertation, revealing intricate information of optical properties never revealed before. On a broader perspective, the PSTD suite has opened up new possibilities by providing rigorous solution to tissue optics---the problem of light scattering by macroscopic biological random media. |
