Incoherent Branched Flow of Light

Abstract

Waves traveling in weakly disordered media possessing long-range correlations experience a universal phenomenon known as branched flow, where the waves split and form channels (branches) of enhanced intensity that keep dividing as the waves propagate. Branched flow effects have been studied experimentally in various systems, thus far always with coherent waves. We present the first experimental observation of branched flow of spatially incoherent light. We show that the primary effect of branching occurs for both coherent and incoherent light, but each pronounced branch is accompanied by sidelobes arising from interference, which disappear when the waves are incoherent. The position of the first caustic, where the branches reach peak intensity, remains the same as the coherence is reduced, but the branch statistics changes and some branches blur or disappear.