Broadband enhanced backscattering spectroscopy of strongly scattering media

Abstract

Abstract:We report on a new experimental method for enhanced backscattering spectroscopy (EBS) of strongly scattering media over a bandwidth from 530-1000 nm. The instrument consists of a supercontinuum light source and an angle-dependent detection system using a fiber-coupled grating spectrometer. Using a combination of two setups, the backscattered intensity is obtained over a large angular range and using circularly polarized light. We present broadband EBS of a TiO 2 powder and of a strongly scattering porous GaP layer. In combination with theoretical model fits, the EBS system yields the optical transport mean free path over the available spectral window.

Angle dependence of the frequency correlation in random photonic media: Diffusive regime and its breakdown near localization

“…Circular polarization is used to suppress single-scattering contributions in the coherent backscattering cone, which would otherwise result in a reduced enhancement factor. 21 The spectral correlation function was obtained at each angle by averaging the correlation functions from 50 spectra taken at different sample positions. The correlation function was averaged over a spectral range from 550 to 850 nm, yielding an average over several thousands of individual speckles.…”

“…The mean free path of the sample ranges between 0.55 and 0.9 μm in the visible part of the spectrum. 21 The thin TiO 2 slabs have been investigated before using time-resolved transmission, and were found to be within the limits of classical diffusion description. 18 In the reflection experiments of Sec.…”

Large Photonic Strength of Highly Tunable Resonant Nanowire Materials

“…Model fits to the data are indicated by the red lines in Figure 1b, using an internal reflection correction given by the extrapolation lengths in Table 1. 28 These fits yield values of the transport mean free path l t and optical thickness L/l t of the slab as shown in Figure 1c. A continuous decrease of l t is observed for increasing nanowire diameters, reaching a lowest value of 0.16 ( 0.02 µm.…”

“…In addition to the single-wavelength measurements, we have explored the spectral variation of light scattering by the nanowires using a broad-band EBS technique specially developed for this purpose. Experimental details of this technique are presented in ref 28. Panels d-f of Figure 2 show the EBS spectra of the three nanowire materials with increasing wire diameters.…”

Broadband coherent backscattering spectroscopy of the interplay between order and disorder in three-dimensional opal photonic crystals

“…We employ a broad-band coherent backscattering technique using a supercontinuum white-light source. 23 The technique has been used successfully to investigate Photonic crystal effects influencing the apparent mean free path: 1. modification of source of diffuse light by Bragg diffraction, 2. modification of angle-dependent escape probability due to internal reflection. strongly photonic random media, i.e.…”