Simultaneous temperature and electric field measurements via Rayleigh scattering and E-FISH for reduced electric field quantification.

Motivated by a need to directly measure the reduced electric field in non-equilibrium plasmas, this Letter demonstrates an optical diagnostic capable of simultaneously measuring gas temperature and electric field strength. This method, which combines both coherent and incoherent light scattering, is based on a standard electric field-induced second harmonic (E-FISH) generation (line-of-sight) light collection setup while concurrently imaging the frequently overlooked elastic Rayleigh scattering (RS) orthogonal to the laser propagation. Good agreement between experiments and theory is observed, notably in the case of E-FISH, whose signal has explicit dependencies on temperature via both its density and phase mismatch (index of refraction) contributions. Superior agreement is achieved only if the actual temperature distribution along the axis of laser propagation is considered. We expect this method to find utility in plasma-assisted applications for reduced field quantification where background interference is manageable, and major species compositions remain relatively constant.