Whole Life-cycle of Superfilament in Water From Femtoseconds up to Microseconds

摘要

A whole life-cycle of the superfilamentation in water in tight focusing geometry was investigated. In this regime a single continuous plasma channel is formed. To achieve this specific regime the principal requirement is the usage of tight focusing and supercritical power of laser radiation. They together clamp the energy in the ultra-thin (approximately several microns) channel with a uniform plasma density distribution in it. The superfilament becomes a center of cylindrical cavitation bubble area and shock wave formation. The length of the filament increases logarithmically with laser pulse energy. The linear absorption decreases the incoming energy delivered to the focal spot, which dramatically complicates the filament formation, especially in the case of loose focusing. Aberrations added to the optical scheme lead to multiple dotted plasma sources for shock wave formation, spaced along the axis of pulse propagation. Increasing the laser energy launches the filaments at each of the dot, whose overlapping leads to enhance the length of the whole filament.