Nonlinearly driven memory loss of incubation effects in fused silica excited by near single-cycle laser pulses

The nonlinear interaction of near-infrared ultrashort laser pulses with bulk fused silica at intensities below the catastrophic damage threshold is the birthplace of local electronic excitation events that may relax as point defects. The accumulation of defect centers creates additional sources of electronic excitation, gradually lowering the ionization threshold upon multi-pulse irradiation. However, the use of the near single-cycle sub-4 fs pulses erases in a surprising manner the contribution of defects to the damage threshold. This is the result of increasing the strong intensity clamping that limits energy density and therefore carrier collisional multiplication. Thus, the role of additional defect sources in the overall carrier population becomes secondary. In addition, the significant broadening of the near single-cycle pulse may enable impulsive depletion of defect levels, providing a possible additional pathway contributing to the suppression of nonlinear ionization memory.