Light scattering properties of random mediawith a structure of laser speckle

摘要

We study the light scattering properties of random media which have the refractive index distribution of three-dimensional (3D) clipped laser speckle structures. To evaluate the performance of the speckle media as random lasercavities, we calculated the energy density and the local quality factor inside the media by means of the 3D finitedifference time domain (FDTD) method. It is shown that the random media fabricated with the use of three specklewaves superposed without interference have the scattering strength as large as that of particulate media usedconventionally for random laser media. To realize the speckle random media, we employed a technique of holographiclithography and fabricated polymer random media by illuminating photopolymer with one or two speckle waves. The farfield scattering pattern of the sample media was measured to estimate the refractive index distribution of the samples.The experimental results suggest that a fibrous index structure, which is characteristic of 3D speckle patterns, is formedinside the sample media.