Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses

TL;DR

This paper explores using multi-colour laser pulses to generate high-energy isolated attosecond pulses, demonstrating the feasibility with existing high-power laser technology and potential for significant energy enhancement.

Contribution

It introduces a novel multi-colour gating technique for IAP generation, combining theoretical analysis with experimental pulse characterization to enable high-energy attosecond pulses.

Findings

Multi-colour driving pulses can effectively gate IAP generation.

Experimental realization of auxiliary pulses with shorter duration.

Theoretical predictions show potential for high-energy IAP sources.

Abstract

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.