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Observation of backward high-harmonic emission from solids.
Optics Express
|May 3, 2018
Summary
Researchers achieved backward emission of high-harmonics from MgO and Si crystals, enabling phase matching for solid-state sources. This offers higher flux than current transmission-based methods.
Area of Science:
- Nonlinear optics
- Solid-state physics
- Laser-matter interactions
Background:
- High-harmonic generation (HHG) is typically studied in gases.
- Transmission geometry in solids suffers from strong absorption, limiting efficiency.
- Backward emission of high-harmonics from solids has not been fully explored.
Purpose of the Study:
- To experimentally demonstrate backward emission of high-harmonics from crystalline solids.
- To investigate the angular dependence of backward high-harmonic emission.
- To explore the potential of backward emission for phase matching and solid-state HHG sources.
Main Methods:
- Using a near-infrared laser to irradiate MgO and Si crystals.
- Measuring high-harmonic emission in the specular reflection direction.
- Comparing backward emission with transmission geometry.
Main Results:
- Backward emission of high-harmonics was successfully demonstrated from MgO and Si.
- High-harmonic power variation with the angle of incidence was predicted using nonlinear reflection coefficients.
- Backward-propagating high-harmonics serve as a reference for nonlinear light propagation in solids.
Conclusions:
- Backward high-harmonic emission from solids is a viable phenomenon.
- This emission mechanism facilitates phase matching, crucial for efficient HHG.
- Solid-state HHG sources utilizing backward emission could surpass gas-phase sources in flux.
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