Direct time-resolved plasma characterization with broadband terahertz light pulses

Area of Science:

• Plasma Physics
• Spectroscopy
• Ultrafast Science

Background:

• Accurate characterization of laser-induced plasmas is crucial for understanding various physical phenomena.
• Traditional plasma diagnostics can be complex and may not offer single-shot, high-dynamic-range measurements.

Purpose of the Study:

• To develop and demonstrate a novel diagnostic technique for comprehensive plasma characterization.
• To enable in situ, real-time measurement of key plasma parameters using time-resolved terahertz (THz) absorption spectroscopy.

Main Methods:

• Propagation of ultrabroadband (0.1-50 THz) THz pulses through a laser-created plasma.
• Analysis of the time-resolved absorption spectra of the transmitted THz pulses.
• Application of spectral analysis to determine plasma density, electron temperature, and expansion dynamics.

Main Results:

• Demonstrated proof-of-principle for THz absorption spectroscopy as a plasma diagnostic tool.
• Reliably measured plasma densities in the range of 10^16 to 10^20 cm^-3.
• Successfully reconstructed peak intensity within the plasma and observed early plasma evolution stages.

Conclusions:

• THz absorption spectroscopy provides a direct, in situ, and high-dynamic-range method for plasma characterization.
• This technique offers potential for single-shot measurements of plasma parameters.
• The method is effective for studying laser-induced plasmas and their early dynamics.