Controlled polar asymmetry of few-cycle and intense mid-infrared pulses

We demonstrate synthesis of ultrabroadband and phase-locked two-color transients in the multi-terahertz frequency range with amplitudes exceeding 13 MV cm−1. Subcycle polar asymmetry of the electric field is adjusted by changing the relative phase between superposed fundamental and second harmonic components. The resultant broken symmetry of the field profile is directly resolved via electro-optic sampling. Access to such waveforms provides a direct route for control of low-energy degrees of freedom in condensed matter as well as non-perturbative light–matter interactions under highest non-resonant electric bias.