We have investigated nonlinear laser ̶ matter interaction inside silicon under tight focusing conditions by continuously tuning driving pulse duration from femtosecond to picosecond timescales. Such tailoring of laser pulse width provides a new route for energy delivery into a microvolume avoiding two-photon absorption and plasma defocusing in the pre-focal region. As a result, we have achieved values of saturated deposited energy density and plasma electron concentration of as high as 1 kJ cm −3 and 10 19 cm −3 respectively, which is lower than the threshold of irreversible structural transformation. For further increase of energy delivery inside silicon, a two-color technique supported by extremely tight focusing can be realized, forming a roadmap to the 3D industrial micromachining of planar bulk silicon.

中文翻译：

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在块状硅中紧密聚焦的Cr：镁橄榄石激光辐射非线性传播下脉冲持续时间对能量传递的影响

我们通过连续地调整飞秒至皮秒的驱动脉冲持续时间，研究了在严格聚焦条件下硅内部非线性激光̶物质的相互作用。激光脉冲宽度的这种调整为将能量传递到微体积中提供了一条新途径，从而避免了双光子吸收和焦点前区域中的等离子体散焦。结果，我们获得的饱和沉积能量密度和等离子体电子浓度的值分别高达1 kJ cm -3和10 19 cm -3，这低于不可逆结构转变的阈值。为了进一步增加硅内部的能量传递，可以实现由非常紧密的聚焦支持的双色技术，从而形成了对平面体硅的3D工业微加工的路线图。