Extreme THz fields from two-color filamentation of midinfrared laser pulses
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2018 American Physical Society. Nonlinear THz photonics is probably the last frontier of nonlinear optics. The strength of both the electric and the magnetic fields of these ultrashort low-frequency light bunches opens the way to exciting science and applications. Progress in the field though is slow because of the deficiency in suitable sources. Here we show that two-color filamentation of midinfrared 3.9m laser pulses allows one to generate single-cycle THz pulses with multimillijoule energies and record conversion efficiencies. Moreover, the focused THz peak electric and magnetic fields reach values of GV/cm and kT, respectively, exceeding by far any available quasi-dc field source today. These fields enable extreme field science, including into other, relativistic phenomena. In addition, we elucidate the origin of this high efficiency, which is made up of several factors, including a mechanism where the harmonics produced by the midinfrared pulses strongly contribute to the field symmetry breaking and enhance the THz generation.