arXiv subjects

Sebastien Weber

Publications and source records attributed to Sebastien Weber.

2 recordsLinked to original sources

arXiv2026

Unveiling nanolaser physics: Non-Perturbative Measurement of the Lasing-Mode Photon Population at the Sub-Picoseconds and Nanometer Scale

Semiconducting nanowire lasers (NWLs) constitute nanometer-scale modular and tunable light sources hence an essential component for integrated opto-electronics. However, improving and optimizing NWL operation requires characterization of their near-field and dynamics at the nanometer scale, which is hampered by the light diffraction limit. In this article, we show how to non-perturbatively measure the absolute number of photons in the nanolaser cavity above the lasing threshold with sub-picosecond resolution using a GaN nanowire nanolaser, as well as map the lasing mode spatial profile at the nanoscale. This technique, based on the simultaneous measurements of the photon induced near-field electron microscopy (PINEM) and the photons far-field, allows for the complete nanoscale and time-resolved characterization of a NWL in operation while monitoring its macroscopic optical properties.

physics.optics↗

arXiv2009

Molecular vibrational cooling by Optical Pumping with shaped femtosecond pulses

Some of us have recently reported in Science 321 232 (2008) vibrational cooling of translationally cold Cs_2 molecules into the lowest vibrational level v=0 of the singlet X 1Sigma_g ground electronic state. Starting from a sample of cold molecules produced in a collection of vibrational levels of the ground state, our method was based on repeated optical pumping by laser light with a spectrum broad enough to excite all populated vibrational levels but frequency-limited in such a way to eliminate transitions from v=0 level, in which molecules accumulate. In this paper this method is generalized to accumulate molecules into an arbitrary selected "target" vibrational level. It is implemented by using ultrashort pulse shaping techniques based on Liquid Crystal spatial light modulator. In particular a large fraction of the initially present molecule is transferred into a selected vibrational level such as v=1, 2 and 7. Limitations of the method as well as the possible extension to rotational cooling are also discussed.

physics.atom-ph↗