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Cross-polarized and stable second harmonic generation from monocrystalline copper.
Elif Nur Dayi1, Omer Can Karaman1, Diotime Pellet1
1Laboratory of Nanoscience for Energy Technologies (LNET), STI, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
Nanophotonics (Berlin, Germany)
|December 22, 2025
Summary
Stable second-harmonic generation (SHG) from monocrystalline copper (Cu) was achieved using novel synthesis methods. This breakthrough enables robust nonlinear nanophotonics and surface-sensitive spectroscopy with copper-based materials.
Area of Science:
- Nonlinear optics
- Surface science
- Materials science
Background:
- Second-harmonic generation (SHG) is a surface-specific nonlinear optical technique.
- Plasmonic nanomaterials enhance SHG, but material instability often limits studies to gold.
- Copper is a significant plasmonic metal for catalysis, yet its use in nonlinear optics is hindered by degradation.
Purpose of the Study:
- To demonstrate stable and anisotropic SHG from monocrystalline copper.
- To overcome challenges of surface degradation in copper for optical applications.
- To establish copper as a viable material for nonlinear nanophotonics.
Main Methods:
- On-substrate synthesis of atomically flat and oxidation-resistant copper microflakes.
- Reliable SHG measurements under continuous femtosecond excitation.
- Characterization of surface symmetry and optical robustness.
Main Results:
- Stable and anisotropic SHG signal observed from monocrystalline copper microflakes.
- Demonstrated remarkable optical robustness with signal stability over 3 hours of excitation.
- Revealed a strong cross-polarized SHG response with C3v surface symmetry.
Conclusions:
- Monocrystalline copper is a viable and robust platform for nonlinear nanophotonics.
- The developed synthesis approach enables reliable SHG spectroscopy on copper.
- Expands the application range of copper in optical technologies and surface-sensitive analysis.
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