  Xerogel matrices, made by sol-gel techniques, are embedded with polystyrene
spheres to promote multiple scattering of light. Varying the concentration of
the spheres inside the matrix allows one to adjust the transport mean free path
of light inside the material. Coherent backscattering measurements show that a
range of transport mean free paths from 90 to 600 nm is easily achieved. The
determination of the matrix refractive index permits a direct comparison to
multiple scattering and Mie theory. Such tunable diffusive sol-gel derived
samples can be further optimized as random laser materials.
