Sub-cycle millijoule-level parametric waveform synthesizer for attosecond science

The availability of high-energy pulses with durations shorter than the period of their carrier frequency (sub-cycle) will reveal new regimes of strong-field light–matter interactions. Parametric waveform synthesis (that is, the coherent combination of carrier-envelope-phase-stable pulses that emerge from different optical parametric amplifiers) is a promising technology for the realization of tailored optical waveforms with scalable spectral bandwidth, energy and average power. Here we use parametric waveform synthesis to generate phase-controlled sub-cycle waveforms at the millijoule energy level with excellent stability. Full control over the synthesized waveforms (currently spanning 1.7 octaves with full-width at half-maximum durations down to 2.8 fs, that is, 0.6 optical cycles at a central wavelength of 1.4 μm) enables the creation of extreme ultraviolet isolated attosecond pulses via high-harmonic generation without the need for additional gating techniques. The synthesized electric field is directly measured by attosecond-resolution sampling, which also showcases the waveform stability. Optical waveforms with a 1.7 octave spectrum and 0.6 optical cycle duration are generated at a central wavelength of 1.4 μm by parametric waveform synthesis. The output pulse energies amount to >500 μJ with fluctuations of 1% r.m.s. over 1,000 shots.