Flux conservation in coherent backscattering and weak localization of light

The standard theoretical description of coherent backscattering, according to which maximally crossed diagrams accounting for interference between counterpropagating path amplitudes are added on top of the incoherent background, violates the fundamental condition of flux conservation. In contrast to the predictions of previous theories, we show that including maximally crossed diagrams with one additional scattering event does not restore flux conservation. Instead, we propose that the latter is recovered when treating the effects of coherent backscattering and weak localization in a unified framework. On the basis of this framework, we demonstrate explicitly flux conservation in leading order of the weak disorder parameter 1/(kℓ).