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Trajectory analysis for low-order harmonic generation in two-color strong laser fields.
Optics Express
|January 6, 2023
Summary
Two-color laser fields generate ultrashort, ultra-broadband low-order harmonics. A trajectory method bridges macroscopic and microscopic theories, explaining phase-dependent yields and enabling ultrafast electron dynamics reconstruction.
Area of Science:
- Attosecond science
- Quantum optics
- Nonlinear optics
Background:
- Low-order harmonic generation (LHG) in gas-phase media is driven by intense laser fields.
- Existing models, like the photocurrent and strong-field approximation, offer macroscopic and microscopic perspectives, respectively.
- A unified theoretical framework is needed to reconcile these views.
Purpose of the Study:
- To analytically bridge macroscopic and microscopic theories of low-order harmonic generation.
- To utilize the trajectory method for understanding phase-dependent harmonic generation.
- To explore the potential of LHG for reconstructing ultrafast electron dynamics.
Main Methods:
- Analytical derivation connecting macroscopic and microscopic theories using the trajectory method.
- Phase-dependent analysis of terahertz (THz) and third-harmonic generation (THG).
- Investigation of electron wavepacket dynamics and interference phenomena.
Main Results:
- Established a clear correspondence between macroscopic and microscopic theories of LHG.
- Explained phase-dependent THz and THG yields and spectral shapes through coherent superposition of electron trajectories.
- Demonstrated that electron self-interference underlies observed harmonic characteristics.
Conclusions:
- The trajectory method provides a unified understanding of LHG.
- Phase dependence in LHG arises from the interference of electron trajectories.
- LHG holds promise for probing and reconstructing ultrafast electron dynamics.
