Single-cycle infrared waveform control

Tailoring the electric-field waveform of ultrashort light pulses forms the basis for controlling nonlinear optical phenomena on their genuine, attosecond timescale. Here we extend waveform control from the visible and near-infrared—where it was previously demonstrated—to the mid-infrared spectral range. Our approach yields single-cycle infrared pulses over several octaves for the first time. Sub-10-fs pulses from a carrier-envelope-phase-stabilized, Kerr-lens-mode-locked, diode-pumped Cr:ZnS laser drive cascaded intrapulse difference-frequency generation and control the electric-field evolution of the resulting coherent emission over 0.9–12.0 μm. Sub-cycle field control in this wavelength range will be instrumental for launching and steering few-femtosecond electron/hole wavepackets in low-gap materials, extending the bandwidth of electronic signal processing to multi-terahertz frequencies, as well as for electric-field-resolved molecular fingerprinting of biological systems. Continuously adjustable single-cycle waveform spanning from 0.9 to 12.0 μm is obtained by cascaded intrapulse difference-frequency generation in a ZnGeP 2 crystal. The cascade-associated phase response—distinct for different spectral bands—provides a new tuning parameter for waveform adjustment.