Propagation Of Stochastic Electromagnetic Beams In The Biological Tissues

Recently, the vector theory of the coherent property of light field has become a hot topic in optics. Meanwhile, the field of biological tissues has received a lot of attention recently. The propagation of the stochastic electromagnetic beams in the biological tissues connected the two fields. In this thesis, we investigate the properties of stochastic electromagnetic beams on propagation through turbulent biological tissues, and derive some useful propagation formulas. We also get the evolution rules about the transmission characteristics such as the spectral density, the spectral degree of coherence and the spectral degree of polarization of beams.Chapter 1:We introduce the research background and the research progress of the beam propagation, the fundamental method and theoretical basis used in our work. The unified theory of coherence and polarization and the partially coherent optics are also outlined.Chapter 2:On the basis of the generalized diffraction integral formula for turbulent systems in spatial domain, an analytical propagation expression for the elements of the cross-spectral density matrix of a random electromagnetic beam passing through the turbulent biological tissues is derived. Some analyses are illustrated by numerical examples relating to changes in the state of polarization of an electromagnetic Gaussian Schell-mode beam propagating through such a turbulent biological tissues system. It is shown that the isotropic sources and the anisotropic sources have different statistical properties on propagation.Chapter 3:Analytical formulae for the elements of cross-spectral density matrix of the vortex beams propagating through the turbulent biological tissues are derived. With the help of the formulae, the changes in characteristics of the beam such as the spectral density, the spectral degree of coherence and the spectral degree of polarization of the anisotropic vortex beam and isotropic vortex beam are illustrated and compared by numerical examples. It is shown that the changes of the statistical properties of the vortex beam mainly depend on the correlation length and the topological charge of the vortex beam.Chapter 4:The propagation formula for the elements of the cross-spectral density matrix of the ultrashort pulsed Bessel-Gauss beams passing through the turbulent biological tissues is derived. With the help of this formula, we study the power spectra and the transversal intensity distribution of the ultrashort pulsed Bessel-Gauss beams passing through the turbulent biological tissues, and we obtained that there is a remarkable spreading of the transversal intensity beyond the diffraction-free range.Chapter 5:Our work is outlined and more work to be done in future is proposed.