Four-wave mixing diagnostics for neutrals, ions and electrons in low (and high) temperature plasmas*

Single shot, non-resonant, laser-based four-wave mixing (FWM) diagnostics provide a novel way to characterize the thermodynamic state (T, N, v) of neutral gas and plasma flows with high spatio-temporal resolution and signal-to-noise-ratio (SNR) due to their coherent nature. We present progress in using intense optical lattices for radial and axial measurement of the thermodynamic state of neutrals in a glow discharge through single shot Rayleigh-Brillouin scattering (CRBS)[1], [2], prior to its use in arc discharges. Additionally, we demonstrate a similar FWM chirping concept for a novel coherent Thomson scattering scheme [3]. We also discuss single shot CRBS for ultrafast ionization and thermalization in nanosecond repetitively pulsed discharges (NRPs), driving Langmuir waves in a plasma, and performing coherent diagnostics to reveal electronic temperature and density [4]. Finally, we demonstrate the utilization of single shot CRBS for the fundamental and detailed understanding of nanoparticle synthesis by plasma.

[1] A. Gerakis, M. N. Shneider, and P. F. Barker. "Single-shot coherent Rayleigh–Brillouin scattering using a chirped optical lattice." Optics letters 38, no. 21 (2013): 4449-4452.

[2] R. Randoph, S. Suzuki, K. Hara, and A. Gerakis, "Simultaneous neutral density and temperature measurements of neutral species in plasma with single-shot coherent Rayleigh-Brillouin scattering", Manuscript submitted

[3] Mokrov, M., M. N. Shneider, and A. Gerakis. "Analysis of coherent Thomson scattering from a low temperature plasma." Physics of Plasmas 29, no. 3 (2022).

[4] Alfaro, G. F., N. Shneider, and A. Gerakis. "Analysis of an induced Langmuir wave by ponderomotive forces and its applicability for plasma diagnostics", Manuscript submitted