Investigation of 1.06 μm laser induced plasma in air using optical interferometry

The laser produced plasma in air by Q-switch Nd:YAG pulses with 50 mJ and 7 ns was analyzed using Mach–Zehnder interferometer. The interferograms were taken at various delay times after single pulses induced gas breakdown. The 3D electron density distribution at early times of the plasma is investigated. To determine the 3D electron density distribution of the plasma, the FFT analysis is applied to extract the phase of the reconstructed interferograms and the numerical inverse Abel transformation is used to calculate the refractive index. The results provide an understanding of the electron density temporal and spatial evolution of laser induced plasma in air from 18 ns and up to 100 ns of plasma lifetime.