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| Hauptverfasser: | , , , |
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| Format: | Preprint |
| Veröffentlicht: |
2025
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| Online-Zugang: | https://arxiv.org/abs/2507.20829 |
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| _version_ | 1866910191213084672 |
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| author | Schöpa, Samuel Wiechmann, Falk-Erik Fennel, Franziska Bauer, Dieter |
| author_facet | Schöpa, Samuel Wiechmann, Falk-Erik Fennel, Franziska Bauer, Dieter |
| contents | We utilize few-level model systems to analyze the polarization and phase properties of below-threshold harmonics generated from aligned molecules. In a two-level system, we find that the phase of emitted harmonics undergoes a distinct change. For harmonics with photon energies below the transition energy between the dominant field-dressed states, the phase alternates by $π$ between successive odd harmonic orders. In contrast, the phase remains constant for harmonics above the transition energy. Exploiting this behavior, we construct a four-level model composed of two uncoupled two-level systems aligned along orthogonal directions. We demonstrate that with selected transition frequencies lower-order harmonics follow the polarization of the linearly polarized driving field while higher-order harmonics exhibit a mirrored polarization. The model predicts that aligned systems with orthogonal transition dipoles may show analogous phase and polarization features in the below-threshold regime. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_20829 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Phase structure of below-threshold harmonics in aligned molecules: a few-level model system Schöpa, Samuel Wiechmann, Falk-Erik Fennel, Franziska Bauer, Dieter Quantum Physics Atomic Physics Optics We utilize few-level model systems to analyze the polarization and phase properties of below-threshold harmonics generated from aligned molecules. In a two-level system, we find that the phase of emitted harmonics undergoes a distinct change. For harmonics with photon energies below the transition energy between the dominant field-dressed states, the phase alternates by $π$ between successive odd harmonic orders. In contrast, the phase remains constant for harmonics above the transition energy. Exploiting this behavior, we construct a four-level model composed of two uncoupled two-level systems aligned along orthogonal directions. We demonstrate that with selected transition frequencies lower-order harmonics follow the polarization of the linearly polarized driving field while higher-order harmonics exhibit a mirrored polarization. The model predicts that aligned systems with orthogonal transition dipoles may show analogous phase and polarization features in the below-threshold regime. |
| title | Phase structure of below-threshold harmonics in aligned molecules: a few-level model system |
| topic | Quantum Physics Atomic Physics Optics |
| url | https://arxiv.org/abs/2507.20829 |