High-order harmonics enhancement in laser-induced plasma

Area of Science:

• Physics
• Quantum Optics
• Plasma Physics

Background:

• High-order harmonic generation (HHG) is a key process for producing coherent extreme ultraviolet (XUV) and soft X-ray radiation.
• Enhancing HHG efficiency is crucial for advancing applications in spectroscopy, microscopy, and attosecond science.
• Laser-induced plasmas offer a versatile medium for HHG, but efficiency improvements are needed.

Purpose of the Study:

• To demonstrate and evaluate four distinct methods for enhancing strong high-order harmonics generated from femtosecond laser pulses in laser-induced plasma.
• To investigate the spectral ranges where each enhancement technique is most effective.
• To understand the factors limiting the combined application of these enhancement methods.

Main Methods:

• Resonance enhancement via selection of specific ablation targets.
• Quasi-phase-matching for spectrally tunable harmonic groups.
• Two-color laser pumping of the plasma.
• Generation of harmonics in nanoparticle-containing plasmas.

Main Results:

• Significant enhancement of coherent XUV photon generation observed in specific spectral regions (62 nm and 30-50 nm).
• Up to 50-fold increase in overall harmonic yield demonstrated in indium plasma.
• Individual techniques showed effectiveness in different spectral ranges.

Conclusions:

• Multiple techniques can effectively enhance high-order harmonic generation in laser-induced plasmas.
• The choice of technique depends on the desired spectral range for harmonic output.
• Limitations exist in simultaneously applying all four methods within the same spectral region.