M. Ospeck et S. Fraden, INFLUENCE OF REFLECTING BOUNDARIES AND FINITE INTERFACIAL THICKNESS ON THE COHERENT BACKSCATTERING CONE, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 49(5), 1994, pp. 4578-4589
We investigate the effect of reflecting boundary conditions on the sha
pe of the coherent backscattering (CB) cone of light by measuring the
CB cone from a suspension of microspheres as a function of the thickne
ss of the glass window containing the sample. The reflection from the
air-glass interface is observed to narrow the cone, as previously pred
icted and observed; however, the finite thickness of the window introd
uces a slope discontinuity in the CB cone. The dominant contribution t
o the cone for angles less than the kink is from reflected light, whil
e the cone at angles higher than the kink arises from light that direc
tly leaves the sample. Thus the study of the CB cone as a function of
window thickness offers an experimental method of separating the compo
nent of the cone due to interfacial reflectivity from the directly bac
kscattered component. Monte Carlo simulations of the path length distr
ibution of multiply scattered light were performed and compared well w
ith both measurement and theories incorporating reflecting interfaces.
It was found that under certain circumstances an interface of finite
width lowered the CB cone height. Additionally, high quality measureme
nts of the CB cone from Mie scatterers revealed an anisotropy in the c
one similar to the case of Rayleigh spheres. Finally, the influence of
reflecting boundaries on the decay of the temporal autocorrelation fu
nction and the height of the CB cone were investigated.