Lateral scattered light used to study laser light propagation in turbid media phantoms

Understanding laser light propagation in soft tissue is important because of the growing biomedical applications of lasers and the need to optically characterize the biological media. Following previous developments of our group, we have developed low cost models, Phantoms, of soft tissue. The process was developed in a clean room to avoid the medium contamination. Each model was characterized by measuring its refractive index, and spectral reflectance and transmittance. To study the laser light propagation, each phantom was illuminated with a clean beam of laser light, using sources such as He-Ne (632nm) and DPSSL (473 nm). Laterally scattered light was imaged and these images were digitally processed. We analyzed the intensity distribution of the scattered radiation in order to obtain details of the beam evolution in the medium. Line profiles taken from the intensity distribution surface allow measurement of the beam spread, and expressions for the longitudinal (along the beam incident direction) and transverse (across the beam incident direction) intensities distributions were found. From these behaviors, the radiation penetration depth and the total coefficient of extinction have been determined. The multiple scattering effects were remarkable, especially for the low wavelength laser beam.