Space–time distribution of CO2 laser radiation on the surface of a target in the presence of an optical-breakdown plasma

An experimental investigation was made of the refraction of microsecond CO₂ laser pulses in a surface-breakdown plasma. The existence of the focusing and defocusing stages depended on the interaction parameters such as the pulse energy, focusing angle, and density of the surrounding air. A correlation was found between the space–time distribution of the radiation reaching a target and the stages of development of the surface breakdown. A qualitative theoretical explanation of the results was also provided.