Ultrafast optics of solid density plasma using multicolor probes.

Area of Science:

• Plasma Physics
• Laser-Plasma Interactions
• Ultrafast Phenomena

Background:

• Understanding the dynamic properties of hot, dense plasmas is crucial for fields like inertial confinement fusion.
• Previous studies often used single-color probes, limiting the resolution of rapid plasma evolution.

Purpose of the Study:

• To investigate the time-resolved optical properties (reflectivity and transmissivity) of laser-induced hot, dense plasma.
• To explore the influence of probe wavelength on plasma response.
• To determine electron-ion collision frequencies in dense plasmas.

Main Methods:

• Generation of hot, dense plasma from a fused silica target using a high-intensity (2 × 10^17 W cm⁻²) 30 fs laser pulse.
• Employing a multicolor probe beam with wavelengths at 800 nm, 400 nm, and 266 nm for time-resolved measurements.
• Utilizing a simple model of probe absorption via inverse bremsstrahlung to analyze plasma parameters.

Main Results:

• Observed a sub-picosecond transition in plasma reflectivity and transmissivity.
• Demonstrated a clear wavelength-dependent behavior in both reflected and transmitted signals.
• Quantified electron-ion collision frequencies across different plasma densities.

Conclusions:

• The multicolor probe technique effectively captures ultrafast plasma dynamics.
• Wavelength-dependent optical responses provide insights into plasma density and electron-ion interactions.
• The findings contribute to a more comprehensive understanding of laser-produced plasmas.