Abstract

When light is scattered through a randomly in homogeneous medium, backscattering within a narrow cone is enhanced.¹ This enhancement occurs because of the phase coherence between waves that travel the same paths in opposite directions. Recently, a femtosecond laser with a synchroscan streak camera was used to measure the enhanced backscattering.² However, the technique is equipment-intensive. In our experiment, a simpler setup using the CCD array and cw lasers, such as a He-Ne, are used to measure the coherent peaks from biological tissues. Unlike from a liquid medium with scattering particles, the images from a solid surface show specklelike fluctuations. Ensemble averaging is required to reveal the coherent peak. The peak shapes are influenced by the beam polarization. With the polarization parallel to the plane of incidence, a sharper peak is observed. In addition, the relation of the peak shape to the optical properties such as transport mean free path and absorption length are discussed.

© 1991 Optical Society of America