Terahertz acoustics in hot dense laser plasmas

Area of Science:

• Plasma Physics
• Fluid Dynamics
• Acoustics

Background:

• High-intensity lasers interacting with plasma can induce complex phenomena.
• Understanding hydrodynamic processes in extreme conditions is crucial.

Purpose of the Study:

• To investigate a previously unobserved hydrodynamic phenomenon.
• To characterize ultrahigh frequency acoustic disturbances in laser-induced plasma.

Main Methods:

• Generation of plasma using a 30 fs, 800 nm high-intensity laser (∼5×10^16 W/cm^2).
• Picosecond scale observations using pump-probe reflectometry and pump-probe Doppler spectrometry.
• Comparison of experimental data with hydrodynamic simulations.

Main Results:

• Observation of purely hydrodynamic ultrahigh frequency acoustic disturbances in the terahertz (THz) frequency range (1.9±0.6 THz).
• Acoustic waves generated due to differential flow velocities down a density gradient in laser-heated plasma.
• Experimental results are well reproduced by hydrodynamic simulations.

Conclusions:

• The study reveals a novel hydrodynamic mechanism for THz acoustic wave generation.
• This work provides new insights into laser-plasma interactions and high-frequency acoustics.
• The findings open avenues for further research in extreme hydrodynamics.