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.

持续时间短于其载波频率（子周期）周期的高能量脉冲的可用性将揭示强场光与物质相互作用的新机制。参数波形合成（即，来自不同光学参量放大器的载波-信封-相位稳定脉冲的相干组合）是一种实现具有可扩展光谱带宽，能量和平均功率的定制光学波形的有前途的技术。在这里，我们使用参数波形合成来生成具有出色稳定性的毫焦耳能级的相位控制子周期波形。完全控制合成波形（当前跨度为1.7个八度音阶，半高全宽为2.8 fs，即中心波长为1时为0.6个光学周期。4μm）无需额外的选通技术，即可通过高谐波产生而产生极紫外隔离的阿秒脉冲。合成电场通过阿秒分辨率采样直接测量，这也显示了波形稳定性。