Mette Gaarde
Les and Dot Broussard Alumni Professor of Physics Louisiana State University
- Baton Rouge LA
Dr Gaarde's research focuses on the theory of ultrafast laser-matter interactions in atomic, molecular, and solid systems
Areas of Expertise
Biography
Research Focus
High-Order Harmonic Generation & Attosecond Dynamics
Dr. Gaarde’s research focuses on ultrafast atomic, molecular, and optical physics—strong-field laser–matter interactions, high-order harmonic generation, and attosecond dynamics in atoms, molecules, and solids. She uses ab initio and semiclassical modeling, macroscopic propagation simulations, and time-resolved spectroscopy theory to design coherent XUV sources and decode electron motion on attosecond timescales.
Education
University of Copenhagen
Ph.D.
Physics
1997
University of Copenhagen
M.S.
Physics
1994
Accomplishments
Distinguished Research Master
2023
Louisiana State University
Distinguished Faculty Award
2019
Louisiana State University
Fellow
2015
Optica
Fellow
2011
American Physical Society
Media Appearances
Opinion | Letters: La. senators must oppose cuts to science that would devastate our universities
NOLA online
2025-07-02
The budget negotiations for FY2026 are ongoing in Washington. The cuts proposed in the president’s budget would devastate Louisiana’s universities, stifle our innovation pipeline and stall the technical workforce training our economy relies on.
Articles
Super-resolution stimulated X-ray Raman spectroscopy
Nature2025
Propagation of intense X-ray pulses through dense media has led to the observation of phenomena such as atomic X-ray lasing,, self-induced transparency and stimulated X-ray Raman scattering (SXRS). SXRS has been long predicted as a means to launch and probe valence-electron wavepackets and as a building block for nonlinear X-ray spectroscopies,. However, experimental observations of SXRS to date,, have not provided spectroscopic information, and theoretical modelling has largely implemented hard-to-realize phase-coherent attosecond pulses. Here we demonstrate SXRS with spectroscopic precision, that is, detection of valence-excited states in neon with a near Fourier-limited joint energy–time resolution of 0.1 eV–40 fs. We used a new covariance analysis between statistically spiky broadband incident X-ray and scattered X-ray Raman pulses.
Going visible: Attosecond solitons
Nature Photonics2025
Attosecond pulses in the optical regime, formed as solitons during infrared laser-pulse compression in a hollow-core fibre, may open up attosecond science in molecules and solids.
Bringing weak transitions to light
Nature Communications2025
Weak transitions between quantum states are of fundamental importance for a broad range of phenomena from analytical biochemistry to precision physics, but generally challenge experimental detection. Due to their small cross sections scaling with the absolute square of their transition matrix elements, spectroscopic measurements often fail in particular in the presence of competing background processes. Here we introduce a general concept to break this scaling law and enhance the transition probability by exploiting a stronger laser-coupled pathway to the same excited state. We demonstrate the concept experimentally by attosecond transient absorption spectroscopy in helium atoms. The quasi-forbidden transitions from the ground state 1s2 to the weakly coupled doubly excited 2p3d and sp2,4− states are boosted by an order of magnitude.
Quantitative comparison of high-order harmonic yields in ring-shaped organic molecules calculated using time-dependent density-functional theory
Physical Review A2025
We compare the high-harmonic-generation (HHG) yield driven by a midinfrared laser field in three organic ring-shaped molecules, calculated using time-dependent density-functional theory (TDDFT). We average the yield over the relative orientation of the molecules and the linearly polarized, 1825-nm driving laser pulse to compare to experimental spectra obtained by Alharbi et al., [Phys. Rev. A 92, 041801 (2015)1050-294710.1103/PhysRevA.92.041801]. We find that the raw TDDFT-calculated HHG yield in cyclohexane is strongly overestimated compared to those of benzene and cyclohexene, and that this can be attributed to unphysically large contributions from cyclohexane orbitals lying well below the highest-occupied molecular orbital.
Resonant propagation of extreme-ultraviolet pulses through strongly driven high-density media
Physical Review Research2025
We show that by combining strong-field dressing and resonant propagation of XUV pulses, the transition of absorption lines from their natural Lorentzian profiles through Fano and complex multipeak shapes all the way back to broadened near-Lorentzian profiles can be achieved, in the limit of optically thick samples. The final stage of this spectral modification can be understood in terms of a significant temporal stretching and delay of the resonant XUV pulse as it propagates through the dense gas, which alters the ultrafast absorption that is modified by the time-synchronized few-femtosecond laser pulse. We first demonstrate this concept in numerical calculations, both using a model system and through a fully coupled solution of the time-dependent Schrödinger equation and the Maxwell wave equation.
Media
