Les and Dot Broussard Alumni Professor of Physics
Ph.D., 1997 - University of Copenhagen, Denmark
Louisiana State University
Department of Physics & Astronomy
215-B Nicholson Hall, Tower Dr.
Baton Rouge, LA 70803-4001
Ultrafast Atomic, Molecular and Optical Physics - Theory
My research program is centered around probing and controlling the ultrafast laser-matter interactions in atomic, molecular, and condensed-phase systems, involving a wide range of ultrafast dynamics. Our studies include both the production and application of attosecond and femtosecond pulses of coherent VUV and XUV light, and lies in the interface between ultrafast AMO science and extreme non-linear optics. Attosecond pulses, which are generated through the extremely nonlinear process of high harmonic generation (HHG), are the shortest bursts of light ever produced and allow for probing and controlling the dynamics of bound electrons on their natural time scales.
In the LSU ultrafast AMO theory group we do many different types of calculations to address these dynamics. At the microscopic level, studying the dynamics of the individual quantum system, we use the time-dependent Schrödinger equation, time-dependent density functional theory, or the semi-conductor Bloch equations. A long-time focus of my research has been the interplay between the microscopic (quantum) effects and the macroscopic (classical) effects that govern many intense laser-matter interactions. To this end we solve coupled equations for the microscopic response (as above) with the Maxwell wave equation in real time, and at the sub-cycle level, which requires large-scale computations. We are currently applying these different models to four different types of projects:
Transient absorption and reshaping of attosecond pulses: Attosecond transient absorption (ATA) spectroscopy is a pump-probe scenario in which an attosecond XUV pulse and a delayed but synchronized IR pulse can be used to study electron dynamics on its natural time scale. We study a range of ATA phenomena in atoms, molecules, and solids using a time-domain description that allows us to treat on an equal footing all the different linear and nonlinear processes by which the medium can exchange energy with the XUV and IR fields, see [1-3] below. Much of this work has been done in collaboration with experimental groups in the US and Europe.
Probing ultrafast charge migration: Our goal is to measure and control the quantum dynamics of electrons and holes in polyatomic molecules through the signatures that the hole motion imprints on high order harmonics emitted by these molecules. This project is a multi-institutional collaboration between theory at LSU, and experiments at the Ohio State University and the University of Virginia, see [4,5] below.
Ultrafast dynamics in transparent solids: Recent experimental and theoretical results have shown that not only is it possible to generate high order harmonics, and potentially attosecond pulses, from transparent solids - we can also learn a lot about ultrafast electron dynamics in the condensed phase by studying the HHG process. See press release about recent Nature paper, a collaboration between LSU theory and experiments at SLAC National Accelerator Laboratory and Stanford University: https://www.lsu.edu/physics/news/2016/06/20160606-frozen-argon.php and [6-7] below.
Filamentation of intense mid-infrared (MIR) laser pulses: When intense pulses propagate through air, they can form a so-called filament in which several highly nonlinear processes balance each other to allow for propagation over long distances without collapse or substantial energy loss. As part of a multi-institutional project spanning many labs in the US and Europe, we are currently investigating novel effects in filamentation of few-cycle MIR pulses, see [8-9] below.
Current and Select Publications
- A. P. Fidler, S. J. Camp, E. R. Warrick, E. Bloch, H. J. B. Marroux, D. M. Neumark, K. J. Schafer, M. B. Gaarde, and S. R. Leone, Nonlinear XUV Signal Generation Probed by Attosecond Transient Grating Spectroscopy (link to https://www.nature.com/articles/s41467-019-09317-4), Nature Communications 10, 1384 (2019).
- S. Bengtsson, E. W. Larsen, D. Kroon, S. Camp, M. Miranda, C. L. Arnold, A. L’Huillier, K. J. Schafer, M. B. Gaarde, L. Rippe, and J. Mauritsson, Controlled free-induction decay in the extreme ultraviolet (link to https://www.nature.com/articles/nphoton.2017.30), Nature Photonics 11, 252 (2017).
- M. Wu, S. Chen, S. Camp, K. J. Schafer, and M. B. Gaarde, Theory of strong-field attosecond transient absorption (link to https://iopscience.iop.org/article/10.1088/0953-4075/49/6/062003/meta), Topical Review, J. Phys. B 49, 062003 (2016).
- F. Mauger, P. Abanador, T. Scarborough, T. Gorman, P. Agostini, L. F. DiMauro, K. Lopata, K. J. Schafer, and M. B. Gaarde, High-harmonic spectroscopy of transient two-center interference calculate with time-dependent density-functional theory (link to https://aca.scitation.org/doi/full/10.1063/1.5111349), Structural Dynamics 6, 044101 (2019).
- T. T. Gorman, T. D. Scarborough, P. M. Abanador, F. Mauger, D. Kiesewetter, P. Sandor, S. Khatri, K. Lopata, K. J. Schafer, P. Agostini, M. B. Gaarde, and L. F. DiMauro, Probing the Interplay between Geometric and Electronic-Structure Features via High-Harmonic Spectroscopy (link to https://aip.scitation.org/doi/full/10.1063/1.5086036), J. Chem. Phys. 150, 184308 (2019).
- C. Q. Abadie, M. Wu, and M. B. Gaarde, Spatio-temporal filtering of high order harmonics in solids (link to https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-21-5339), Opt. Lett. 43, 5339 (2018).
- G. Ndabashimiye, S. Ghimire, M. Wu, D. A. Browne, K. J. Schafer, M. B. Gaarde, and D. A. Reis, Solid-state harmonics beyond the atomic limit (link to https://www.nature.com/articles/nature17660), Nature 534, 520 (2016).
- J. M. Brown, A. Couairon, P. Polynkin, and M. B. Gaarde, Analysis of the angular spectrum for ultrashort laser pulses (link to https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.063421), JOSA B 36, A105 (2019).
- J. M. Brown, A. Couairon, and M. B. Gaarde, Ab-initio calculations of the linear and nonlinear susceptibilities of N2, O2, and air in the mid-infrared (link to https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.063421), Phys. Rev. A 97, 063421 (2018).
- M. B. Gaarde, J. L. Tate, and K. J. Schafer, Macroscopic aspects of attosecond pulse generation (link to https://iopscience.iop.org/article/10.1088/0953-4075/41/13/132001/meta), Topical Review, J. Phys. B 41, 132001 (2008). Selected as one of 50 most influential papers in Journal of Physics. (link to https://iopscience.iop.org/article/10.1088/0953-4075/49/21/210501)
For a full list of publications see here