SUPERCONTINUUM GENERATION VERSUS OPTICAL-BREAKDOWN IN CO2 GAS

Threshold powers for optical breakdown (OB) and supercontinuum (SC) generation in high-pressure CO2 gas have been measured at different focusing conditions. It has been found that by varying the focal length of the focusing lens, it is possible to pass from the case of OB without SC generation, through OB with SC generation, and into SC without OB. The experimental results demonstrate that plasma formation is not an essential mechanism for SC generation, whereas self-focusing causes SC generation characteristics to be dependent on conditions of external focusing.