Study on spin angular momentum balance in harmonics generated from counter-rotating two-color laser fields.

Area of Science:

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

Background:

• High-order harmonic generation (HHG) is a key process in strong-field physics.
• Understanding spin angular momentum transfer in HHG is crucial for attosecond science.
• Two-color driving fields offer enhanced control over HHG spectra.

Purpose of the Study:

• To investigate spin angular momentum transfer in HHG from xenon driven by counter-rotating two-color fields.
• To theoretically explain the experimentally observed V-type and Λ-type harmonic spectra.
• To establish a theoretical framework for spin conservation in complex driving fields.

Main Methods:

• Quantum-field scattering theory is employed to model the HHG process.
• Elliptically polarized fields are decomposed into counter-rotating circularly polarized components.
• Phased generalized Bessel functions are used to describe harmonic generation amplitudes.

Main Results:

• The conservation of spin angular momentum during HHG in two-color fields is rigorously derived.
• Theoretical models successfully reproduce the experimentally observed V-type and Λ-type harmonic spectral distributions.
• A substantial balance pattern of spin angular momentum transfer is disclosed.

Conclusions:

• Spin angular momentum transfer is a fundamental aspect of HHG in counter-rotating two-color fields.
• The theoretical framework provides a solid basis for understanding spin dynamics in complex laser fields.
• This work offers insights into controlling and interpreting HHG spectra for advanced applications.