ELECTRON DENSITY DETERMINATION OF LASER INDUCED PLASMA FROM POLYMETHYL METHACRYLATE USING PHASESmFT DETECTION TECHNIQUE

Irradiation of a Polymethyl methacrylate target using a pulsed Nd-YAG laser causes pluma formation in the vicinity of the target. The refractive index gradient dQl! to tbe presence of the plasma is probed using phase-shift detection technique. Tbe phase-shift technique is a simple but sensitive te<:hnique for the determination of laser ablation threshold of solids. The number density of laser generated plasma ahove the ablation threshold from Polymethyl methacrylate is calculated as a function of laser ftuence. The number density varies from 2 x 1016 em-3 to 2 x 1011 cm-3 in the ftuenee interva