Electron Acceleration by Self-focusing of Mid-IR Laser Pulses at Critical Plasma Densities

Daniel Woodbury, University of Maryland, College Park

Recently we demonstrated acceleration of electrons to few MeV energies in high-density gas jet targets using sub-terawatt, ultrashort, near-infrared laser pulses. Here we extend these studies into the mid-infrared spectral range (using 3.9 micron, 100 fs sub-terawatt pulses), which enables near- and above-critical density interactions with moderate-density jets. We present thresholds for electron acceleration based on critical parameters for relativistic self-focusing and target width, as well as trends in the electron beam profiles and spectra. Due to the wavelength scaling, we were able to obtain clear time-resolved images of relativistic self-focusing of the laser pulse using multi-shot transverse interferometry. Our results pave the way for developing shaped, high-density gas targets for electron acceleration with novel long wavelength drivers.

Abstract Author(s): D. Woodbury, L. Feder, V. Shumakova, C. Gollner, B. Miao, R. Schwartz, A. Pugzlys, A. Baltuska, H.M. Milchberg