Spatially and spectrally resolved quantum-path tracing in high-order harmonic generation

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Optics
• Nonlinear Optics

Background:

• High harmonic generation (HHG) is a key process for producing extreme ultraviolet (XUV) and soft X-ray radiation.
• Understanding the quantum pathways governing HHG is crucial for controlling the emitted light.
• Previous studies have explored HHG dynamics, but macroscopic evolution with spatial and spectral resolution remains an active area of research.

Purpose of the Study:

• To experimentally demonstrate the macroscopic evolution of quantum-path distributions in harmonic emission.
• To investigate the splitting of harmonic spatial profiles into red and blue shifts with increasing laser intensity.
• To clarify the spatial and spectral origins of these shifts by controlling the focal position.

Main Methods:

• Experimentally generating high harmonic emission from an argon gas jet using a driving laser.
• Utilizing spatial and spectral resolution to analyze the harmonic emission.
• Varying the driving laser intensity to observe macroscopic evolution.
• Adjusting the focal position to trace quantum-path distributions.

Main Results:

• Observed macroscopic evolution of quantum-path distributions in harmonic emission.
• Demonstrated the splitting of harmonic spatial profiles into red and blue shifted components with increasing laser intensity.
• Experimentally traced and clarified the red and blue shifts in quantum-path distributions in both spatial and spectral domains.
• Confirmed the influence of focal position on the observed shifts.

Conclusions:

• The study provides a comprehensive understanding of macroscopic quantum-path evolution in harmonic emission.
• The observed splitting and spectral shifts offer insights into controlling harmonic generation.
• These findings pave the way for better control and application of high harmonic emission.