CREOL COLLOQUIUM SERIES: Dr. Michaël Hemmer '11PhD, JILA University of Colorado Boulder

Monday, November 6, 2023 11 a.m. to noon

Title: Ultrafast Long Wavelength Lasers: A New Field of Opportunities

Abstract: Up until two decades ago, laser development was mostly centered in the near-infrared spectral region. While this spectral region is well-suited for a number of applications it is sub-optimum for frequency down-conversion to the mid-IR and THz because of Manley-Rowe limitations and limited availability of suitable nonlinear crystals. Similarly, when attempting up-conversion via high harmonic generation, near-infrared lasers constitute a limit to scaling existing coherent tabletop EUV sources to the soft X-ray spectral range.
A number of fundamental physics scaling rules suggest however that ultrafast, high energy, high average power, long wavelength laser light can overcome the limitations experienced at near infrared wavelengths. For instance, energy and momentum conservation rules show that driving parametric down-conversion with long wavelength lasers provides a boost in conversion efficiency. Similarly, ponderomotive scaling rules show that driving high harmonic generation with long wavelength lasers allows the production of keV coherent radiation in a tabletop setting. In addition, both critical plasma density and normalized vector potential scale favorably at long wavelength suggesting the potential of truly tabletop laser wakefield accelerators – or even colliders.
The development of long wavelength lasers has long been hampered by technological limitations. Recently however, a convergence of technological advances and high demand for these lasers has allowed rapid progresses toward the development of reliable, ultrafast mid-IR sources that can be used directly or to drive secondary sources of either photons or particles. In this talk, I will review some of the recent progress toward the development of such laser sources, the challenges ahead and the exciting new applications long wavelength sources and long wavelength driven secondary sources will enable in the near future.

About the Speaker: Dr. Hemmer graduated with a Masters degree in engineering from the Ecole Nationale Supérieure de Physique de Marseille (France). He graduated with a PhD in Optics in 2011 from the University of Central Florida working on the development of ultrafast nonlinear amplifiers for high field physics applications. He then was a post-doctoral associate and later a research fellow at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain. There he worked on the development of long wavelength, ultrafast lasers. These lasers have been used for high harmonic generation into the soft X-ray region and for ultrafast electron diffraction experiments. He then moved to the Deutsches Elektronen Synchrotron (DESY), in Hamburg, Germany as a researcher and worked on the development of laser driven electron gun and electron accelerators with the ultimate goal of providing an all-laser driven hard X-ray source. He joined JILA at CU Boulder in the summer of 2018 and has since then been working on developing a mid-IR laser facility to drive high harmonics into the soft X-ray with stability compatible with challenging experiments.

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