  Isolated attosecond pulses (IAP) generated by high-order harmonic generation
are valuable tools that enable dynamics to be studied on the attosecond time
scale. The applicability of these IAP would be widened drastically by
increasing their energy. Here we analyze the potential of using multi-colour
driving pulses for temporally gating the attosecond pulse generation process.
We devise how this approach can enable the generation of IAP with the available
high-energy kHz-repetition-rate Ytterbium-based laser amplifiers (delivering
180-fs, 1030-nm pulses). We show theoretically that this requires a
three-colour field composed of the fundamental and its second harmonic as well
as a lower-frequency auxiliary component. We present pulse characterization
measurements of such auxiliary pulses generated directly by white-light seeded
OPA with the required significantly shorter pulse duration than the that of the
fundamental. This, combined with our recent experimental results on
three-colour waveform synthesis [Phys. Rev. X 4, 021028 (2014)], proves that
the theoretically considered multi-colour drivers for IAP generation can be
realized with existing high-power laser technology. The high-energy driver
pulses, combined with the strongly enhanced single-atom-level conversion
efficiency we observe in our calculations, thus make multi-colour drivers prime
candidates for the development of unprecedented high-energy IAP sources in the
near future.
