Comparative study of medium length-dependent high-harmonic generation from metal ions

Area of Science:

• Laser-induced plasma physics
• Nonlinear optics
• Atomic and molecular physics

Background:

• High-harmonic generation (HHG) is a crucial process for producing coherent extreme ultraviolet (XUV) and soft X-ray radiation.
• Understanding the factors influencing HHG in various media, such as laser-ablated metal plumes, is essential for optimizing light sources.

Purpose of the Study:

• To experimentally compare high-harmonic yields from laser-ablated metal ion plumes (W, Mo, Cr, Cu, Ni, Fe, Ag, Mg).
• To determine and compare ion density and single-atom response characteristics for different metal targets.
• To extract coherence length, absorption length, and single-atom response strength using a theoretical model.

Main Methods:

• Experimental measurement of high-harmonic yields as a function of medium length for various metal targets.
• Fitting experimental data to a theoretical model to extract key parameters.
• Analysis of the relationship between target properties (e.g., melting temperature) and plume characteristics.

Main Results:

• Coherence lengths were found to decrease monotonically with increasing harmonic order for all metal targets.
• Ion densities were estimated from the coherence length trends, with lower melting point targets generally exhibiting higher densities.
• Single-atom response strengths varied, with species having one electron in the outermost subshell showing weaker responses.

Conclusions:

• The study provides insights into the relationship between target material properties and high-harmonic generation efficiency in laser-ablated plumes.
• The findings contribute to understanding the fundamental processes governing HHG in dense, ionized media.
• The extracted parameters (coherence length, absorption length, single-atom response) are valuable for modeling and optimizing HHG sources.