M.P. van Albada

Femtosecond time-resolved measurements of weak localization of light

Abstract Time-resolved backscattering of coherent light from a disordered medium under weak localization conditions has been observed for the first time with femtosecond resolution using a light-gating technique based on second-harmonic generation. The time dependence of the observed enhanced backscattering is consistent with simple diffusion theory.

An accurate technique to record the angular distribution of backscattered light

We report on a new technique to record the angular distribution of light which is scattered from a (disordered) material around the backscattering direction. The technique is accurate over a large scanning range (500 mrad) which includes the exact backscattering direction, and the angular resolution is high (100 μrad). The technique is particularly suitable for the study of coherent backscattering from very strongly scattering random media, but it can be applied in any situation where the angular distribution of backscattered light is studied. It allowed us to measure for the first time the theoretical value of two of the enhancement factor in coherent backscattering.

Polarisation effects in weak localisation of light

Enhanced backscattering from a random medium resulting from interference is known as weak localisation. In the backscattered light three polarisation effects are observed: there is partial retention of polarisation, the polarised cone of enhanced backscattering is spatially anisotropic, and a slight enhancement is found in the depolarised light component. It is proved experimentally that the three effects are due to lower-order scattering contributions, and the effects are explained. A computer simulation of enhanced backscattering from a medium containing randomly distributed Rayleigh scatterers confirms this interpretation.

Depolarization of femtosecond laser pulses in disordered media

Abstract Depolarization of coherent light waves in disordered media has been studied directly in the time-domain with femtosecond time resolution. The experimental results are compared with recent results from calculations for Rayleigh scattering in random media.

Isomerzation of bromotolouenes under the influence of Al2Br6.HBr

Abstract The isomerization of the bromotoluenes in radioactive toluene with Al2Br6 as a catalyst was investigated. The isomerizations ortho-para and para-ortho are completely intermolecular, and are in agreement with the catalytic bromination mechanism given by Olah. The isomerization and formation of the meta-bromotolouene involve an intramolecular 1,2-shift.

Towards Observation of Anderson Localization of Light

Localization of waves is associated with the presence of interference effects in multiple scattering. In this paper we discuss light scattering experiments on strongly scattering random media consisting of small dielectric particles (TiO2, polystyrene) in a medium (airy water). Experimental observations include observation of interference in backscattering (weak localization) and study of transport. Experiments are compared with theories, and effects which are the consequence of the vector nature of light are explained. On the basis of experimental results we speculate about the possibility to observe strong localization of light.

Accurate Measurement of Backscattered Light from Random Media

Anderson localization is known as the phenomena of a dramatic change in the transport properties of electrons when they are subject to a spatially random potential. [1] Electron waves are multiple scattered and as a consequence of interference, the diffusion constants vanishes. The dimension of the system plays a crucial role for the occurrence of Anderson localization. In one and two dimensions any de-gree of disorder will lead to a finite localization length, whereas in three dimensions first a critical mean-free path should be reached to enter the localized regime: (1)