Fresnel absorption, resonance absorption, and x rays in laser-produced plasmas

Area of Science:

• Plasma Physics
• Laser-Matter Interaction
• X-ray Generation

Background:

• High-intensity lasers interacting with matter create plasmas.
• Understanding light absorption and energy conversion is crucial for plasma diagnostics and applications.
• Previous models did not fully explain experimental observations in laser-produced plasmas.

Purpose of the Study:

• To investigate the differing absorption mechanisms of s- and p-polarized light in laser-produced plasmas.
• To explain the observed differences in X-ray emission intensity and efficiency between the two polarizations.
• To correlate plasma parameters with light absorption and subsequent X-ray production.

Main Methods:

• Utilizing subpicosecond high-intensity KrF laser pulses.
• Analyzing experimental data on reflectance for s- and p-polarized light.
• Modeling light absorption using Fresnel and resonance absorption assumptions.
• Comparing X-ray emission thresholds, intensity, and production efficiency.

Main Results:

• Fresnel absorption for s-polarized light and resonance absorption for p-polarized light accurately model experimental reflectance.
• Significant differences in X-ray emission thresholds (above 0.5 keV), intensity, and efficiency were observed.
• Resonant absorption of p-polarized light occurs at the critical density.
• S-polarized light is absorbed at a higher electron density.

Conclusions:

• The distinct absorption mechanisms for s- and p-polarized light explain the observed experimental features.
• Resonant absorption of p-polarized light at critical density leads to more efficient X-ray production compared to s-polarized light absorption at higher densities.
• This understanding is vital for optimizing X-ray generation in laser-plasma interactions.