Conservation of energy in coherent backscattering of light

Abstract

Although conservation of energy is fundamental in physics, its principles seem to be violated in the field of wave propagation in turbid media by the energy enhancement of the coherent backscattering cone. In this letter we present experimental data which show that the energy enhancement of the cone is balanced by an energy cutback at all scattering angles. Moreover, we give a complete theoretical description, which is in good agreement with these data. The additional terms needed to enforce energy conservation in this description result from an interference effect between incident and multiply scattered waves, which is reminiscent of the optical theorem in single scattering.

Broadband enhanced backscattering spectroscopy of strongly scattering media

“…The cone normalized to the linear-polarization nonconserving channel has a slightly narrower width of 6.7 • . It also shows a much flatter background, with a slight undercut which may result from energy conservation in enhanced backscattering [21,22]. However, we find that the far wings of the cone are strongly affected by small misalignments in the positioning of the sample at the center of rotation, resulting in either a slight undercut, as in Fig.…”

Coherent Backscattering and Anderson Localization of Light

“…8, the result of such a correction is shown. Here the incoherent reference was a teflon sample, where the absorption was determined using a time of flight measurement (Fiebig, Aegerter, Bührer, Störzer, Montambaux, Akkermans and Maret [2007]). Also shown in the figure is a corrected theory, taking into account the fact that when the mean free path gets smaller than the wave-length of light, the time-reversed paths start to overlap.…”

“…Such a corrected theory is shown by the dashed line. Data from Fiebig, Aegerter, Bührer, Störzer, Montambaux, Akkermans and Maret [2007].…”

“…Since this reduction takes place on a length scale of λ, the corresponding reduction of the backscattering enhancement is at high angles. To a first approximation, this correction can be calculated to be (Fiebig, Aegerter, Bührer, Störzer, Montambaux, Akkermans and Maret [2007]):…”

Inelastic Multiple Scattering of Interacting Bosons in Weak Random Potentials

“…Obviously, the total ladder contribution has to be reduced in order to allow for an enhanced backscattering signal without violating flux conservation. Since we neglect this effect here, we note that this reduction of the ladder contribution has been carefully measured [175], and recently the diagrams have been identified which allow one to predict these small corrections within a diagrammatic theory [176].…”