arXiv subjects

Pablo Jara

Publications and source records attributed to Pablo Jara.

2 recordsLinked to original sources

arXiv2026

On-shell compression and reconstruction (OSCAR) of monochromatic wave fields in weakly scattering media

Advances in computational methods have made full-wave simulations in large disordered media increasingly feasible, but the resulting volume of field data, scaling with the cube of the ratio of system size to wavelength, creates a severe storage and post-processing bottleneck. Generic compression methods are sample-specific and preclude operations on compressed data. We introduce OSCAR, a physics-based lossy compression scheme for monochromatic wave fields in weakly scattering media. OSCAR exploits the universal confinement of the Fourier representation of wave fields to a thin dispersion shell, a direct consequence of wave propagation when the scattering mean free path significantly exceeds the wavelength, and a property of every disorder realization rather than of the ensemble average, so that one mask serves an entire ensemble. The resulting compression ratio reflects two distinct scale separations: on-shell confinement due to weak scattering, and the excess Fourier-space volume introduced by sub-wavelength discretization of the scatterers. Crucially, second-order quantities, demonstrated here on sensitivity maps, can be computed via convolution entirely in compressed space while preserving the interference effects. We validate the method in 2D scalar and 3D vector simulations of electromagnetic waves, spanning quasi-ballistic to diffusive transport. The reconstruction error is set by the discarded spectral weight. Demonstrated compression ratios reach ~810x in 2D and ~420x in 3D at a 3% error, with cell-averaged second-order observables accurate to an even smaller error. Tested from quasi-ballistic to diffusive transport, OSCAR stores the fields in up to 19x less space at a 2.5-4.2x lower runtime cost than SZ3. This lowers the storage barrier to ensemble studies at scales relevant to biomedical optics, seismology, and underwater acoustics.

physics.optics↗

arXiv2025

Harnessing coherent-wave control for sensing applications

Imaging techniques such as functional near-infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT) achieve deep, non-invasive sensing in turbid media, but they are constrained by the photon budget. Wavefront shaping (WFS) can enhance signal strength via interference at specific locations within scattering media, enhancing light-matter interactions and potentially extending the penetration depth of these techniques. Interpreting the resulting measurements rests on the knowledge of optical sensitivity - a relationship between detected signal changes and perturbations at a specific location inside the medium. However, conventional diffusion-based sensitivity models rely on assumptions that become invalid under coherent illumination. In this work, we develop a microscopic theory for optical sensitivity that captures the inherent interference effects that diffusion theory necessarily neglects. We analytically show that under random illumination, the microscopic and diffusive treatments coincide. Using our microscopic approach, we explore WFS strategies for enhancing optical sensitivity beyond the diffusive result. We demonstrate that the input state obtained through phase conjugation at a given point inside the system leads to the largest enhancement of optical sensitivity but requires an input wavefront that depends on the target position. In sharp contrast, the maximum remission eigenchannel leads to a global enhancement of the sensitivity map with a fixed input wavefront. This global enhancement equals to remission enhancement and preserves the spatial distribution of the sensitivity, making it compatible with existing DOT reconstruction algorithms. Our results establish the theoretical foundation for integrating wavefront control with diffuse optical imaging, enabling deeper tissue penetration through improved signal strength in biomedical applications.

physics.optics↗