Fully stabilized multi-TW optical waveform synthesizer: Toward gigawatt isolated attosecond pulses

Area of Science:

• Attosecond science
• Nonlinear optics
• X-ray generation

Background:

• High-order harmonic generation (HHG) is a key process for producing coherent X-ray radiation.
• Controlling the temporal and spectral properties of HHG is crucial for advanced applications.
• Previous methods often lacked stability and precise control over the generated X-ray pulses.

Purpose of the Study:

• To demonstrate a stable, multi-channel optical waveform synthesizer for generating high-order harmonic supercontinua.
• To achieve reproducible and intense soft X-ray generation.
• To investigate the advantages of multi-color waveform synthesis over single-color methods.

Main Methods:

• Utilized a 50-mJ, three-channel optical waveform synthesizer.
• Employed a Ti:sapphire pump laser and a two-stage optical parametric amplifier.
• Implemented active stabilization for time delays, relative phases, and carrier-envelope phase.
• Generated a supercontinuum around 60 eV with pulse energy >0.24 μJ.

Main Results:

• Achieved shot-to-shot stable generation of a high-order harmonic supercontinuum spectrum.
• Obtained soft X-ray continuum with peak power >1 GW and 170-as transform-limited duration.
• Identified and established a control scheme for the characteristic delay dependence of the synthesizer.
• Observed a 1-2 order of magnitude enhancement in cutoff spectrum intensity using three-color synthesis compared to one-color.

Conclusions:

• Demonstrated a robust and stable platform for generating intense, coherent soft X-ray radiation.
• Highlighted the significant advantages of multi-color waveform synthesis for enhancing HHG intensity.
• Paved the way for advanced attosecond science applications requiring precisely controlled X-ray pulses.