The influence of DC electric field-enhanced ionization on the self-focusing of femtosecond lasers

Its detection is crucial for the femtosecond filaments application. In this work, an experimental setup with a DC electric field applied at the filament position is proposed for measuring the Pcr of femtosecond lasers.

Measurements results show that the Pcr is significantly reduced with a DC electric field applied, it decreases as the applied voltage increases. This is attributed to the enhanced ionization through the interaction between the applied electric field and the laser-ionized plasma. As both the applied voltage and incident laser power increase, filamentation occurs more easily, and focal shift becomes more pronounced.