Conference Agenda

With the increasing insights into quantum material coexisting phases and intertwined degrees of freedom, the idea of light control of material properties has gained attention, leading to dedicated researches on out-of-equilibrium photo-induced condensed matter phases. The phenomena consecutive to photo-excitation are hence key elements to understand to envision controlling materials with light. In particular, the photo-induced carrier dynamics is essential to apprehend the coupling with the structure.

In this work, I will present our study of photo-induced carrier dynamics in a low bandgap semiconductor InSb, using THz time-domain spectroscopy (THz-TDS) as a sensitive probe for carriers. We extract the carrier dynamics, following a pump excitation at 1030 nm, from the relatively broadband reflectivity at different pump-probe delays. This spectral approach relies on THz generation from optical rectification in an organic BNA crystal, and provides a more complete picture on the dynamics at play. We model the carrier response by a Drude-Lorentz model and propose a simple way to account for the possible mismatch between THz penetration ad carrier diffusion length.

With the same method, we provide insights on carrier dynamics in the topological semimetal ZrTe5, where photo-induced topological phase transition has been recently under investigation.

We present the first Kerr-lens modelocked Tm:KYW laser. Using multimode diode in-band pumping, we achieve 86-fs pulses at 1.1 W and 135-fs at 2.0 W, achieving threefold higher average power than comparable prior Tm-based oscillators

Two-dimensional hexagonal materials, such as transition-metal dichalcogenides, exhibit valley-selective physics that enables ultrafast control of electronic excitations. In nonlinear optics, the K and K′ valleys provide resonant pathways for manipulating excitons, Bloch oscillations, and Floquet states. However, under intense laser fields, coherent carrier dynamics beyond these high-symmetry points remain largely unexplored.

Here, we study ultrafast strong-field dynamics in monolayer WS₂ via high-harmonic generation driven by intense laser pulses. In the perturbative regime, interband resonances at the K/K′ valleys enhance harmonic emission through multiphoton processes. In the strong-field regime, sub-cycle carrier acceleration across the Brillouin zone leads to pronounced quantum interference between multiple excitation pathways, including contributions from regions far from the valleys.

Our measurements are supported by quantum simulations, showing excellent agreement and enabling a time-resolved interpretation of the underlying carrier dynamics. These results highlight the role of laser-driven coherent motion on ultrafast timescales and establish high-harmonic spectroscopy as a sensitive probe of electronic structure across the full Brillouin zone.

This work proposes new routes for harnessing laser-driven quantum interference in two-dimensional hexagonal systems and all-optical techniques to occupy and read-out electronic structures in the full Brillouin zone via strong-field nonlinear optics, advancing quantum technologies.

We report on the generation of high-power relativistic high-order harmonics at 1-kHz repetition rate using the SalleNoire2.0 installation [1] at LOA. A CEP-stable 4 fs, 2.5 mJ driving pulse is tightly focused onto a colliding-jets liquid-leaf target, producing coherent broadband radiation spanning the visible to XUV range (1.5 eV to 35 eV) [2].

The continuous (minutes to hours, see figure) kHz-operation of the source represents a breakthrough for relativistic laser-plasma interactions and enables its use as a stable driver for attosecond experiments requiring very high pulse intensities. Calculations predict that refocused intensities above 10^15 W/cm2 are achievable, opening the way to strong-field studies in the XUV regime. The talk will also present the plans for the experiments aiming to obtain a usable refocused attosecond pulse, including the homegrown Python library used to tolerance the beam transport system.

[1] M. Ouillé et al., ‘Relativistic-intensity near-single-cycle light waveforms at kHz repetition rate’, Light Sci Appl, vol. 9, no. 1, p. 47, Mar. 2020, doi: 10.1038/s41377-020-0280-5.

[2] A. Cavagna et al., ‘Continuous relativistic high-harmonic generation from a kHz liquid-sheet plasma mirror’, Opt. Lett., OL, vol. 50, no. 1, pp. 165–168, Jan. 2025, doi: 10.1364/OL.545912

Coherent tail overlap interactions between ultrashort pulses propagating in microresonator and laser cavities lead to the formation of soliton molecules and complex multisoliton dynamics, including limit cycles, synchronization, and transition to chaos. Even though there is an extensive body of experimental observation and numerical simulation of nonlinear dynamics effects in ultrafast pulse propagation, the theoretical understanding of these phenomena has been qualitative at best. Here we present new families of asymptotically exact equations of motion for soliton pair dynamics in Kerr microresonators, where the solitons interact with a continuous-wave pedestal, and in passively mode locked lasers with asymmetric pulse shapes and non-local gain saturation interaction.

The equations of motion are obtained in the limit of well-separated solitons, where the pulses interact through exponentially decaying oscillatory tails. This motion drives the pairs either toward an attracting soliton-molecule steady state, or away from a repelling configuration. When the pulse shape is asymmetric, the soliton molecule drifts with a constant velocity that is greatly enhanced by gain saturation effects.