With the media lighted by linear polarized Laser beam, the backscattering from tissue has been simulated and then analyzed by Monte Carlo Methods. The investigated scattering particles are polystyrene spheres homogeneously dispersed in de-ionized water, which is used as simulating model of tissue-melanoma. This simulation is based on the Mie theory’s spherical scattering particle model and focused on behavior of photons in the backscattering light from the model of tissue. Numerical results having been obtained and compared, conclusions have been made. We theoretically represent the residual polarizing light intensity keeps high when corresponding maximum depth that the photons used to be is shallow, and vice versa. And the distribution of the backscattering’s polarization properties relate regularly to this depth and melanoma can affect them apparently.
The absorption spectra of Congo red (CR) in aqueous solution and PVA film are measured, respectively. With the Z-scan method, the nonlinear optical properties of CR are investigated, and experimental data on the nonlinear refractive index and the change of refractive index are obtained. As a result, the intensity dependent index n<sub>2</sub> of CR has been determined to be in the range from 10<sup>-10</sup> to 10<sup>-9</sup> m<sup>2</sup>/W. The nonlinear absorption of CR aqueous film and CR-doped PVA film for three wavelengths is measured respectively. Under the condition of that the two samples are irradiated by 443nm or 535nm, the characteristics of absorption as function of the power of 633nm are determined. Finally, the experimental results are analyzed.