Route to attosecond nonlinear spectroscopy.

Area of Science:

• Quantum optics
• Ultrafast science
• Atomic, molecular, and optical physics

Background:

• Generation of coherent light in the deep and vacuum ultraviolet (UV) spectral regions is crucial for advanced spectroscopy.
• Existing methods often face limitations in terms of pulse energy, coherence, or spectral range.

Purpose of the Study:

• To demonstrate the generation of microjoule-scale, low-order harmonic supercontinua in the deep and vacuum UV (4-9 eV).
• To explore the underlying nonlinear physics enabling this process.
• To pave the way for novel spectroscopic techniques probing ultrafast dynamics.

Main Methods:

• Nonlinear transformation of near-single-cycle laser pulses within a gas cell.
• Theoretical modeling to understand the novel nonlinear regime responsible for supercontinuum formation.

Main Results:

• Successful generation of coherent microjoule-scale supercontinua in the 4-9 eV range.
• Identification of a novel nonlinear regime governing the supercontinuum generation process.
• Theoretical validation of the experimental observations.

Conclusions:

• The demonstrated method enables efficient generation of powerful deep-UV and vacuum UV subfemtosecond pulses.
• This capability opens new avenues for pump-probe spectroscopy of subfemtosecond-scale valence-shell phenomena.
• The findings have broad implications for studying ultrafast processes in atoms, molecules, and condensed matter.