Size correction in ultrafast laser processing of fused silica by temporal pulse shaping

Laser structuring of bulk dielectric materials involves focusing through air-dielectric interfaces, which is prone to induce spherical aberrations. This elongates the energy deposition volume and restricts the processing accuracy at large focusing depths. Although spatial phase corrections are commonly applied to correct wavefront distortions, we show that temporal forming of ultrafast laser pulses achieves comparable counteracting function, limiting the spatial extent while creating a dominant region of positive index change. We indicate the role of reduced nonlinearity in plasma formation as a control factor which couples the spatial and temporal responses of the material. (C) 2008 American Institute of Physics.