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Published on: July 12, 2017
High-order harmonic generation from solid targets with 2 mJ pulses.
James H Easter1, Aghapi G Mordovanakis, Bixue Hou
1Center for Ultrafast Optical Science, University of Michigan, 2200 Bonisteel Boulevard, Ann Arbor, Michigan 48109, USA. jheaster@umich.edu
Optics Letters
|October 5, 2010
Summary
High-harmonic generation in solids was achieved using a kilohertz laser and short focal length optics. This method produces low-divergence harmonics with efficiencies comparable to gas-based systems.
Area of Science:
- Physics
- Laser Science
- Nonlinear Optics
Background:
- High-harmonic generation (HHG) is a key process for producing coherent extreme ultraviolet (XUV) and soft X-ray radiation.
- Traditional HHG predominantly utilizes gas-phase media, limiting achievable photon energies and flux.
- Solid targets offer a pathway to higher harmonic orders and potentially more compact HHG sources.
Purpose of the Study:
- To demonstrate high-harmonic generation (HHG) from solid targets using a kilohertz laser system.
- To investigate the feasibility of using a very short focal length optic (f/1.4 paraboloid) for solid-state HHG.
- To characterize the generated harmonics in terms of order, divergence, and conversion efficiency.
Main Methods:
- Focusing 2 mJ, 50 fs laser pulses at 800 nm to a 1.7 μm spot size (FWHM) on solid targets.
- Utilizing a very short focal length paraboloid (f/1.4) in conjunction with a kilohertz repetition rate laser system.
- Operating the system at 500 Hz without employing contrast enhancement techniques.
Main Results:
- Generation of harmonics up to the 18th order from solid targets.
- Achieved low harmonic divergence (<4°) compared to the driving laser beam.
- Observed conversion efficiencies per harmonic greater than 10⁻⁷, comparable to gas-phase HHG.
- Demonstrated HHG using a short focal length optic and a kilohertz laser system, a novel approach.
Conclusions:
- High-harmonic generation from solid targets is feasible with short focal length optics and kilohertz laser systems.
- The generated harmonics exhibit favorable properties, including low divergence and competitive conversion efficiencies.
- This work paves the way for more compact and efficient sources of coherent XUV and soft X-ray radiation.
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