Controllable transport mean free path of light in xerogel matrixes embedded with polystyrene spheres

Abstract

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.

Taking apart the enhanced backscattering cone: Interference fringes from reciprocal paths in multiple light scattering

“…1, is used to observe interference fringes from a series of diffusive samples with different transport mean free paths, in the range 12-215 µm. These diffusive samples are of two origins: commercially available white products (80 g/m 2 paper and Teflon) and homemade suspensions of polystyrene spheres within a sol-gel matrix [10]. Figure 2 visually presents the fringes, measured from both a mirror and a diffusive sample, as a function of the incident optical delay ϕ.…”

“…3, the average amplitude of the fringe Fourier component is plotted as a function of distance between incident spots and for several diffusive samples of known . For each sample, the transport mean free path is determined by the width of a standard EBS cone measurement [10]. The theoretical expectation, from Eq.…”

Tunable Anomalous Scattering and Negative Asymmetry Parameter in a Gain-Functionalized Low Refractive Index Sphere

“…With this perspective, the negative asymmetry parameter plays a crucial role, and it may lead to an unusual multiple light-scattering regime, where the becomes larger than the . This achievement has important applications in many characterization and imaging methods such as the fabrication-tolerant broad-band operation of random spectrometers, where and are needed to be larger than . − A usual low refractive index sphere exhibits large forward scattering and positive g , which imposes severe limitations to achieve large values of and .…”

不同浸液多孔二氧化硅材料中的光传输性质研究

“…Determination of the TMFP is a substantial fundamental problem in the physics of scattering media, which is important for an understanding of the transmission and scattering behaviors in a random system. The TMFP can be determined from measurements of the total diffuse transmission, reflection [7] , and coherent backscattering [8] .…”

“…In other words, the diffusion properties can be easily controlled by changing the concentration, the size of the scatters, and the relative refractive index. Bret et al adjusted the TMFP of light by varying the concentration of spherical particles, as determined by the coherentbackscattering effect [8] . Anderson localization in gallium arsenide powders (n r = 3.5) [9] and a macroporous silicon two-dimensional (2D) photonic structure (n r = 3.4) [10] have been previously reported.…”