Zeptosecond high harmonic keV x-ray waveforms driven by midinfrared laser pulses

Area of Science:

• Quantum optics
• Attosecond science
• Laser-driven phenomena

Background:

• High harmonic generation (HHG) is a key process for producing extreme ultraviolet (XUV) and X-ray light.
• The temporal characteristics of HHG pulses are crucial for ultrafast science applications.
• The choice of laser driver (e.g., near-infrared vs. mid-infrared) can significantly impact the generated X-ray properties.

Purpose of the Study:

• To theoretically investigate the temporal structure of high harmonic X-ray pulses generated by mid-infrared lasers.
• To compare the temporal characteristics of X-ray pulses generated by mid-infrared and near-infrared lasers.
• To explore the potential for generating sub-attosecond X-ray waveforms.

Main Methods:

• Theoretical modeling of high harmonic generation.
• Simulation of electron wave packet dynamics and reencounters with the ion.
• Analysis of the interference effects in high harmonic emission.

Main Results:

• Mid-infrared lasers produce X-ray pulses with distinct temporal structures compared to near-infrared lasers, particularly at high photon energies.
• The femtosecond-scale X-ray bursts exhibit an intrinsic zeptosecond substructure due to multi-electron reencounter interference.
• Regular sub-attosecond X-ray waveforms can be generated by appropriate filtering without chirp compensation.

Conclusions:

• The temporal fine structure of X-ray pulses is highly dependent on the driving laser's infrared wavelength.
• Zeptosecond structuring in high harmonic generation opens new avenues for attosecond X-ray waveform control.
• This work provides a theoretical basis for generating attosecond X-ray pulses for advanced scientific investigations.