Gao Jian, Li Boyuan, Liu Feng, Chen Zi-Yu, Chen Min, Ge Xulei, Yuan Xiaohui, Chen Liming, Sheng Zhengming, Zhang Jie
Key Laboratory for Laser Plasmas (Ministry of Education) and School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University, Shanghai 200240, China.
Phys Rev E. 2020 Mar;101(3-1):033202. doi: 10.1103/PhysRevE.101.033202.
The unique spatial and temporal properties of relativistic high harmonics generated from a laser-driven plasma surface allow them to be coherently focused to an extremely high intensity reaching the Schwinger limit. The ultimately achievable intensity is limited by the harmonic wavefront distortions during the interactions. Here we demonstrate experimentally that the harmonic divergence can be controlled by an optically shaped plasma surface with a prepulse that has the same spatial and temporal distribution as the main laser pulse. Simulations are also performed to explain the experimental observation, and we find that the harmonic wavefront curvature from a dented surface can be precompensated by a convex plasma. Our work suggests an active approach to control the harmonic divergence and wavefront by an optically shaped target. This can be critical for further high harmonics applications.
由激光驱动的等离子体表面产生的相对论性高次谐波具有独特的时空特性，这使得它们能够被相干聚焦到极高强度，达到施温格极限。最终可实现的强度受到相互作用期间谐波波前畸变的限制。在此，我们通过实验证明，谐波发散可以通过具有与主激光脉冲相同时空分布的预脉冲的光学整形等离子体表面来控制。我们还进行了模拟以解释实验观察结果，并且发现凹陷表面产生的谐波波前曲率可以由凸形等离子体进行预补偿。我们的工作提出了一种通过光学整形靶来控制谐波发散和波前的主动方法。这对于进一步的高次谐波应用可能至关重要。
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