  Coherent backscattering (CBS) arises from complex interactions of a coherent
beam with randomly positioned particles, which has been typically studied in
media with large numbers of scatterers and high opacity. We develop a
first-principles scattering model for scalar waves to study the CBS cone
formation in finite-sized and sparse random media with specific geometries. The
results provide new insights into the effects of density, volume size, and
other relevant parameters on the angular characteristics of the CBS cone
emerging from bounded random media for various types of illumination. This work
also highlights some of the potentials and limitations of employing the
coherent backscattering phenomenon to characterize disordered configurations.
The method developed here provides a foundation for studies of the multiple
scattering of complex electromagnetic fields in randomized geometries,
including quantized fields for investigating the effects of the quantum nature
of light in multiple scattering.
