Dramatic cutoff extension and broadband supercontinuum generation in multi-cycle two color pulses

Area of Science:

• Quantum optics
• Attosecond science
• Nonlinear optics

Background:

• High harmonic generation (HHG) is a key process for producing ultrashort light pulses.
• Extending the harmonic cutoff and controlling the generated spectrum are crucial for advanced applications.
• Current methods face limitations in achieving broad spectral coverage and ultrashort pulse durations.

Purpose of the Study:

• To develop a method for markedly increasing electron-recollision kinetic energy.
• To extend the harmonic cutoff to the water-window spectral region.
• To generate broadband supercontinua supporting ultrashort isolated attosecond pulses.

Main Methods:

• Utilizing a combination of a 0.8 μm/13 fs driving pulse and a weaker multi-cycle mid-infrared pulse at 10.4 μm.
• Synthesizing a laser field to lengthen the electron wave packet acceleration distance.
• Analyzing the resulting harmonic spectra and generated pulse characteristics.

Main Results:

• Electron-recollision kinetic energy significantly increased.
• Harmonic cutoff extended to IP+26UP, covering the water-window spectral region.
• Broadband supercontinuum generation observed, with harmonics above IP+15UP becoming continuous.
• Generation of isolated sub-100 attosecond pulses with tunable central wavelength.
• Pulses with duration below one atomic unit of time (24 attoseconds) achieved.

Conclusions:

• The proposed method dramatically extends the harmonic cutoff and enables broadband supercontinuum generation.
• This approach facilitates the generation of isolated sub-100 attosecond pulses.
• The scheme is extendable to longer driving pulses, offering a versatile approach for attosecond science.