Résumé: Single-shot hyperspectral wavefront sensing is essential for applications like spatio-spectral coupling metrology in high-power laser or fast material dispersion imaging. Under broadband illumination, traditional wavefront sensors assume an achromatic wavefront, which makes them unsuitable. We introduce a hyperspectral wavefront sensing scheme based on the Hartmann wavefront sensing principles, employing a multicore fiber as a Hartmann mask to overcome these limitations. Our system leverages the angular memory effect and limited spectral correlation width of the multicore fiber, encoding wavefront gradients into displacements and the spectral information into uncorrelated speckle patterns. This method retains the simplicity, compactness, and single-shot capability of conventional wavefront sensors, with only a slight increase in computational complexity. It also allows a tunable trade-off between spatial and spectral resolution. We demonstrate its efficacy for recording the hyperspectral wavefront cube from single-pulse acquisitions at the Apollon multi-petawatt laser facility, and for performing multispectral microscopic imaging of dispersive phase objects.

Résumé: Scattering of non-classical light is enabling new ways to study and control photon transport. However, advances in this field often rely on simplifying assumptions regarding the quantum light’s generation and its source. In this work, we relax some of these assumptions and probe the behavior of entangled photon pairs passing through a disordered layer after being generated by a randomly scattered pump via spontaneous parametric down-conversion. We experimentally demonstrate that when the photon pairs are generated immediately after the pump is scattered, they retain a sharp angular correlation peak even after propagating through a dynamic scattering medium. Beyond this proof-of-principle experiment, we present a comprehensive theoretical and numerical analysis showing that these correlations persist for arbitrary separations between the pair-generation region and the entrance to the disordered medium, with qualitatively distinct behavior depending on whether scattering occurs before or after pair generation. In particular, we analyze how the width and strength of the angular correlations depend on the distance between the generation region and the disordered layer. When the pairs are generated after the pump is scattered, the correlation width increases with distance, while the correlation strength remains approximately constant. In contrast, when the pairs are generated first and subsequently scattered, the correlation width initially broadens and then narrows, accompanied by a modification in correlation strength. These findings represent a crucial step toward understanding quantum light generation in complex media and potentially exploiting it for quantum technologies.

Résumé: Single-molecule localization microscopy has enabled high-resolution imaging, but the simultaneous detection of multiple fluorophores traditionally relies on spectral-based separation, which is inherently constrained by spectral overlap. Here we introduce brightness demixing, a method for fluorophore discrimination that exploits brightness, which directly depends on the fluorophore extinction coefficient and quantum yield. By oversampling blinking events, we precisely quantify photon flux as a proxy for brightness, enabling robust differentiation of fluorophores independent of their spectral properties, without requiring additional spectral separation. Brightness demixing operates within a single detection channel, eliminating the need for additional spectral filters or cameras. We demonstrate this approach with simultaneous two- and three-target imaging in both two- and three-dimensional configurations. By maintaining single-wavelength excitation and minimizing chromatic aberrations, this method notably enhances multiplexing in single-molecule localization microscopy while remaining fully compatible with existing setups. Brightness Demixing thus offers a simple yet powerful approach for expanding multi-target imaging capabilities in super-resolution microscopy.