Efficient terahertz and Brunel harmonic generation from air plasma via mid-infrared coherent control

Published on 2019-10-08T21:30:47Z (GMT) by
Nonlinear light conversion involves one or more bound-bound, bound-free, free-free, and free-bound transitions, and it is often challenging to interpret the exact conversion mechanisms. Here we use a femtosecond mid-infrared laser to dominantly enhance free-free transitions in terahertz and harmonic generation from air plasma. We find both radiation originate from a common source, ionization-induced plasma currents, and are greatly enhanced when driven at mid-infrared wavelengths. We observe 1% laser-to-terahertz conversion efficiency. With two-color laser fields, we not only generate ultra-broadband radiation from terahertz to petahertz but also investigate the interplay between tunneling ionization, terahertz, and harmonic generation with coherent control.

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Jang, Dogeun; Schwartz, Robert; Woodbury, Daniel; Griff-McMahon, Jesse; Younis, Abdurrahman; Milchberg, Howard; et al. (2019): Efficient terahertz and Brunel harmonic generation from air plasma via mid-infrared coherent control. The Optical Society. Collection.