arXiv subjects

Sébastien Popoff

Publications and source records attributed to Sébastien Popoff.

3 recordsLinked to original sources

arXiv2026

The vanishing distance: a depth-range boundary for dynamic wavefront shaping

Optical imaging and transmission through scattering media conventionally rely on ballistic light, whose power decays exponentially with the optical thickness. Although ballistic light cannot be exploited beyond a certain depth, no simple criterion currently identifies this limit. Therefore, we introduce here the vanishing distance that is defined as the propagation length at which the ballistic power equals the power carried by a single diffuse optical mode. Beyond the vanishing distance, multiply scattered light dominates, which can be harnessed by optical wavefront shaping or by computational reconstructions. We present a simple semi-analytical model for radiance propagation, validated by Monte Carlo simulations and by experiments in both monodisperse and heterogeneous scattering media. From these data, we estimate the vanishing distance and the associated minimum source power. Across representative scattering environments, ballistic light vanishes after about 20 to 40 scattering mean free paths. Unlike the transport mean free path that characterizes the angular randomization of the scattered light, the vanishing distance identifies the loss of the ballistic channel on a modal-power basis. The vanishing distance is thus a two-sided bound: ballistic approaches cannot be efficiently applied beyond it, whereas wavefront shaping of scattered light offers no advantage below it.

physics.optics↗

arXiv2026

Nanosecond wavefront shaping to focus through agitated turbid media

Multiple scattering rapidly scrambles optical fields in fog, snow and turbid water, causing op- timized wavefront corrections to become obsolete on microsecond timescales. Although wavefront shaping enables focusing through static scattering layers, closed-loop control in dynamically evolving media has remained experimentally challenging because the correction bandwidth must approach the intrinsic decorrelation rate of the speckle. Here, we demonstrate closed-loop wavefront shaping with 32 independent degrees of freedom in an agitated turbid medium exhibiting sub-microsecond decorrelation. The medium thickness exceeds the transport mean free path, meaning the far-field speckle autocorrelation is limited to a diffraction-sized grain. Despite the microsecond decorrelation and this multiple-scattering regime, stable focusing is maintained as the correction cycle approaches the intrinsic dynamics of the medium. These results establish an experimentally accessible regime for coherent wave control in rapidly evolving complex media.

physics.optics↗

arXiv2014

Imaging With Nature: Compressive Imaging Using a Multiply Scattering Medium

The recent theory of compressive sensing leverages upon the structure of signals to acquire them with much fewer measurements than was previously thought necessary, and certainly well below the traditional Nyquist-Shannon sampling rate. However, most implementations developed to take advantage of this framework revolve around controlling the measurements with carefully engineered material or acquisition sequences. Instead, we use the natural randomness of wave propagation through multiply scattering media as an optimal and instantaneous compressive imaging mechanism. Waves reflected from an object are detected after propagation through a well-characterized complex medium. Each local measurement thus contains global information about the object, yielding a purely analog compressive sensing method. We experimentally demonstrate the effectiveness of the proposed approach for optical imaging by using a 300-micrometer thick layer of white paint as the compressive imaging device. Scattering media are thus promising candidates for designing efficient and compact compressive imagers.

physics.optics↗