Ignition by laser-induced optical breakdown

Full text: The optical breakdown in air of atmospheric pressure was investigated at the wavelengths 1064 nm and 532 nm, and using a combination of both radiations, as well. The obtained thresholds for optical breakdown at 1064 nm and 532 nm were compared. Furthermore, the generated plasmas have been characterized by their amount of scattered laser light, energy transmission and temporal transmission. During plasma formation in air, an acoustic pressure wave is generated. The acoustic energy is compared to laser pulse energy and is found to be linearly dependant. Moreover, the frequency distribution of the acoustic pressure waves was analyzed. Furthermore, investigations to analyze details of the focal size dependence of ignition were carried out for different pressures and temperatures. Moreover, an energy balance was drawn to find out the quantity of laser energy deposited in the plasma and to gain information about the losses by scattering and transmission. (author)