多波长高次谐波波面重建中样品吸收的影响  

Influence of Sample Absorption on Multi-Wavelength High-Order Harmonic Wavefront Reconstruction

作　　者：梅波 曾志男[1,3] Mei Bo;Zeng Zhinan(State Key Laboratory of High Field Laser Physics,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;University of Chinese Academy of Sciences,Beijing 100049,China;Zhangjiang Laboratory,Shanghai 200120,China)

机构地区：[1]中国科学院上海光学精密机械研究所强场激光物理国家重点实验室,上海201800 [2]中国科学院大学,北京100049 [3]张江实验室,上海200120

出　　处：《中国激光》2023年第23期161-168,共8页Chinese Journal of Lasers

基　　金：国家自然科学基金(91950203,11874374);中国科学院战略先导科技专项(B类)(XDB16)。

摘　　要：高次谐波自身特性的表征是其在超快时间测量中应用的前提,但是由于其所处波段和宽带光源的特性,使得其三维时空相位的完整测量一直是高次谐波表征的难题。多波长高次谐波的相干合成可以获得阿秒脉冲,但是目前阿秒脉冲的相位测量也只能获得一维时域信息。针对以上问题,提出了一种改进的混态叠层衍射成像方案来解决高次谐波的空域测量,成功实现由多个极紫外(EUV)波长构成的高次谐波梳的空域复振幅重建,并研究了样品吸收对空域复振幅重建过程的影响。研究发现,对于多波长高次谐波重建速度和质量,存在最优的样品衍射图案对比度。Objective With its ultrafast time resolution,broadband spectrum,full coherence,and simple generation and selection devices,high-order harmonic generation(HHG)has shown its potential in the fields of ultrafast optics,strong-field physics,and semiconductor imaging.The characterization of the spatial domain properties of the high-order harmonics is important for applications in the attosecond electron dynamics processes.Although spatial measurements such as the Hartmann wavefront sensor(HWFS)and holography have been proposed in many areas,the extreme ultraviolet(EUV)or X-ray wavelength of the high-order harmonics and the difficulty of introducing reference light make spatial measurements of high-order harmonics a challenge.This paper introduces an improved mixed-state ptychography scheme to realize the spatial measurement of high-order harmonics.This approach makes good use of the multiple wavelengths of the high-order harmonics as well as reduces the stability requirements of the light source.We hope that it will be useful for spatial domain measurements of high-order harmonics and for the study of high-order harmonics generation and focusing.Methods In order to reduce the experimental requirement for the reconstruction of high-order harmonics,we try to make use of known information in our algorithm as more as possible and focus only on the reconstruction of the probe;the reconstruction of the sample is not important.Therefore,we modify the existing mixed-state ptychography scheme and introduce two priori conditions:the spectral distribution at different wavelengths and a specific sample with a certain contrast.These priori conditions are easily obtained experimentally.For the first iteration,the probe size is obtained,and then it is substituted into the initial estimated probe along with the priori spectral distribution.Subsequent iterations are performed with the modulus and frequency domain constraints to achieve complex amplitude reconstruction of the probe.The sample is not updated during the iterative process

关 键 词：测量 高次谐波 叠层衍射成像 相位恢复 多波长 

分 类 号：O434[机械工程—光学工程]