Samuel Métais | Searcharxiv

arXiv2024

Ultralow-Noise Optical Parametric Amplifier for Stimulated Raman Scattering Imaging

We present a 40-MHz ultrafast optical parametric amplifier (OPA), tunable from 0.8 to 1 $μ$m, with a relative intensity noise (RIN) matching the shot-noise floor (-160 dB/Hz) above 2 MHz. The OPA is pumped by a 20-W Kerr-lens mode-locked Ytterbium laser and seeded by a a supercontinuum generated in an all-normal-dispersion (ANDi) fiber. With an average output power >1.5 W, this compact and simple scheme is an attractive alternative to synchronously-pumped optical parametric oscillators, especially within the context of stimulated Raman scattering (SRS) imaging. To illustrate the latter, we perform chemical imaging of vinegar droplets in oil by SRS microscopy.

physics.optics↗

arXiv2022

Super-resolved imaging based on spatiotemporal wavefront shaping

A novel approach to improving the performances of confocal scanning imaging is proposed. We experimentally demonstrate its feasibility using acoustic waves. It relies on a new way to encode spatial information using the temporal dimension. By moving an emitter, used to insonify an object, along a circular path, we create a temporally modulated wavefield. Due to the cylindrical symmetry of the problem and its temporal periodicity, the spatiotemporal input field can be decomposed into harmonics corresponding to different spatial vortices, or topological charges. Acquiring the back-reflected waves with receivers which are also rotating, multiple images of the same object with different Point Spread Functions (PSFs) are obtained. Not only is the resolution improved compared to a standard confocal configuration, but the accumulation of information also allows building images beating the diffraction limit. The topological robustness of the approach promises good performances in real life conditions.

physics.optics↗