Xie Chen, Jukna Vytautas, Milián Carles, Giust Remo, Ouadghiri-Idrissi Ismail, Itina Tatiana, Dudley John M, Couairon Arnaud, Courvoisier Francois
Département d'Optique P. M. Duffieux, Institut FEMTO-ST, UMR 6174 CNRS Université de Franche-Comté, F-25030 Besançon cedex, France.
1] Centre de Physique Théorique, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France [2] Laboratoire Hubert Curien, UMR CNRS 5516, Université de Lyon, Université Jean Monnet, F-42000 Saint-Etienne, France.
Sci Rep. 2015 Mar 10;5:8914. doi: 10.1038/srep08914.
An open challenge in the important field of femtosecond laser material processing is the controlled internal structuring of dielectric materials. Although the availability of high energy high repetition rate femtosecond lasers has led to many advances in this field, writing structures within transparent dielectrics at intensities exceeding 10(13) W/cm(2) has remained difficult as it is associated with significant nonlinear spatial distortion. This letter reports the existence of a new propagation regime for femtosecond pulses at high power that overcomes this challenge, associated with the generation of a hollow uniform and intense light tube that remains propagation invariant even at intensities associated with dense plasma formation. This regime is seeded from higher order nondiffracting Bessel beams, which carry an optical vortex charge. Numerical simulations are quantitatively confirmed by experiments where a novel experimental approach allows direct imaging of the 3D fluence distribution within transparent solids. We also analyze the transitions to other propagation regimes in near and far fields. We demonstrate how the generation of plasma in this tubular geometry can lead to applications in ultrafast laser material processing in terms of single shot index writing, and discuss how it opens important perspectives for material compression and filamentation guiding in atmosphere.
飞秒激光材料加工这一重要领域中的一个公开挑战是介电材料的可控内部结构化。尽管高能量高重复率飞秒激光的出现推动了该领域的诸多进展，但在透明电介质中以超过10¹³W/cm²的强度写入结构仍然困难，因为这会伴随着显著的非线性空间畸变。本文报道了一种高功率飞秒脉冲的新传播模式，它克服了这一挑战，这种模式与一种中空、均匀且强烈的光管的产生相关，即使在与致密等离子体形成相关的强度下，该光管仍保持传播不变性。这种模式由携带光学涡旋电荷的高阶非衍射贝塞尔光束引发。数值模拟通过实验得到了定量验证，在实验中一种新颖的实验方法能够直接成像透明固体内部的三维能量密度分布。我们还分析了在近场和远场向其他传播模式的转变。我们展示了在这种管状结构中产生等离子体如何能够在单次折射率写入方面应用于超快激光材料加工，并讨论了它如何为大气中的材料压缩和丝状化引导开辟重要前景。
