LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
Université Paris Sud, Paris, 91400 Orsay, France.
Phys Rev Lett. 2018 Jun 29;120(26):264803. doi: 10.1103/PhysRevLett.120.264803.
The emission of high-order harmonics in the extreme ultraviolet range from the interaction of a short, intense laser pulse with a grating target is investigated experimentally. When resonantly exciting a surface plasmon, both the intensity and the highest order observed for the harmonic emission along the grating surface increase with respect to a flat target. Harmonics are obtained when a suitable density gradient is preformed at the target surface, demonstrating the possibility to manipulate the grating profile on a nanometric scale without preventing the surface plasmon excitation. In support of this, the harmonic emission is spatiotemporally correlated to the acceleration of multi-MeV electron bunches along the grating surface. Particle-in-cell simulations reproduce the experimental results and give insight on the mechanism of high harmonic generation in the presence of surface plasmons.
实验研究了短而强的激光脉冲与光栅靶相互作用时在极紫外范围内产生高次谐波的现象。当共振激发表面等离激元时，谐射线沿光栅表面的强度和最高阶数都相对于平面靶有所增加。在靶表面预先形成合适的密度梯度时，可以获得谐波，证明了在不阻止表面等离激元激发的情况下，可以在纳米尺度上操纵光栅轮廓。实验结果得到了支持，谐射线发射与沿光栅表面加速的多 MeV 电子束的时空相关性。粒子模拟再现了实验结果，并深入了解了存在表面等离激元时的高次谐波产生机制。
