Department of Physics and Astronomy, Queen's University Belfast, BT7 1NN Belfast, United Kingdom.
Phys Rev Lett. 2013 Apr 19;110(16):165002. doi: 10.1103/PhysRevLett.110.165002. Epub 2013 Apr 18.
Beam divergences of high-order extreme ultraviolet harmonics from intense laser interactions with steep plasma density gradients are studied through experiment and Fourier analysis of the harmonic spatial phase. We show that while emission due to the relativistically oscillating mirror mechanism can be explained by ponderomotive surface denting, in agreement with previous results, the divergence of the emission due to the coherent wake emission mechanism requires a combination of the dent phase and an intrinsic emission phase. The temporal dependence of the divergences for both mechanisms is highlighted while it is also shown that the coherent wake emission divergence can be small in circumstances where the phase terms compensate each other.
强激光与陡密度梯度等离子体相互作用产生的高阶极紫外谐波的束散度通过谐波空间相位的实验和傅里叶分析进行了研究。我们表明，尽管由于相对论振动镜机制引起的发射可以用位移动力学表面凹陷来解释，这与先前的结果一致，但由于相干尾流发射机制引起的发射的发散需要凹陷相位和固有发射相位的组合。突出了两种机制的发散的时间依赖性，同时还表明，在相位项相互补偿的情况下，相干尾流发射的发散可以很小。
