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: Semi-analytical methods for modeling guided waves in structures of constant cross-section yield frequency-dependent polynomial eigenvalue problems for the wavenumbers and mode shapes. Solving these eigenvalue problems over a range of frequencies results in continuous eigencurves. Recent research has shown that eigencurves of differentiable parameter-dependent eigenvalue problems can alternatively be computed as solutions to a system of ordinary differential equations (ODEs) obtained by postulating an exponentially decaying residual of a modal solution. Starting from an approximate initial guess of the eigenvalue and eigenvector at a given frequency, the complete eigencurve is obtained using standard numerical ODE solvers. We exploit this idea to develop an efficient method for computing the dispersion curves of plate structures coupled to unbounded solid or fluid media. In these scenarios, the approach is particularly useful because the boundary conditions give rise to nonlinear terms that severely hinder the application of traditional solvers. We discuss suitable approximations of the nonlinearity for obtaining initial values, analyze computational costs and robustness of the proposed algorithm, and verify results by comparison against existing methods.

Résumé: Significance: Reliable quantification of retinal arterial blood flow is important for diagnosing and monitoring ocular and systemic diseases. Existing techniques are limited by invasiveness, motion artifacts, or a lack of quantitative flow estimation. Aim: The aim is to assess the repeatability, reproducibility, and robustness of laser Doppler holography (LDH) for measuring retinal arterial hemodynamics. Approach: We acquired LDH data at 67 kHz in healthy volunteers (14 eyes intra-day and 4 eyes inter-day) and quantified blood volume rate, resistivity index (RI), and vessel diameter. Additional measurements evaluated sensitivity to axial displacement and gaze lateral positioning. Results: LDH successfully measured retinal arterial blood volume rate in all eyes, with a coefficient of variation (CoV) of 18.5% for the mean arterial blood volume rate and a CoV of 11% for RI. Inter-day reproducibility remained acceptable ( formula presented ). The mean arterial diameter estimation showed a CoV of formula presented . Moderate axial or lateral shifts introduced small changes in hemodynamic values ( formula presented CoV) compared with inter- or intra-day tests. Conclusions: LDH provides reliable and robust measurements of retinal arterial hemodynamics and maintains performance under typical imaging variations (axial or gaze position). These findings support its potential for longitudinal studies and future clinical translation.