基于双频光源和涡旋相位的互补旋转集束匀滑方案

Conjugate rotation smoothing scheme for laser quad based on dual-frequency laser and spiral phase plate

提出了一种基于双频光源和涡旋相位板实现光束快速互补旋转的集束匀滑方案。双频光源为集束中各子束提供频移,拓扑荷数相同但反号的涡旋相位板阵列用于将各个子束变换成拉盖尔—高斯(LG)光束,而通过偏振控制则可实现子束间两两的相干叠加。在此基础上,通过采用共轭连续相位板可使波长不同、偏振态不同的子束组合在靶面形成快速旋转且空间上互补填充的焦斑。结果表明,利用这一方案可实现子束散斑在靶面上快速旋转且散斑分布保持互补,进而有效改善靶面辐照均匀性,甚至为抑制激光等离子体不稳定性提供了一种潜在途径。

Conjugate rotation smoothing scheme for laser quad based on dual-frequency laser and spiral phase plate was proposed.The dual-frequency laser provides frequency shift among the beamlets,the spiral phase plates with same helical charge but opposite sign transform the beamlets into Laguerre-Gaussian beams,and the polarization control is applied to make these beamlets coherently superposed on the target plane.On this basis,the conjugate continuous phase plates are adopted to enable the beamlets with different central wavelength and orthogonal polarization form focal spots with rapid rotation.Moreover,the spatiotemporal focal spot of the laser quad looks like conjugate spin light because of the frequency beats.It is indicated that,the scheme enables the fine-scale speckles within the focal spot rotate in a period of a few picoseconds,and even exhibit different intensities and wavelengths at different time and different positions.Hence,the novel scheme can effectively smooth the irradiation uniformity of the laser quad and even has the potential to mitigate laser plasma interactions.