Fisher Information In Measurement Of Carrier–envelope Phase For Few-cycle Laser Pulses

With the rapid development of ultrafast laser technology,it is possible to accurately diagnose the ultrafast light field and measure the ultrafast dynamics of atoms and molecules,.According to the attosecond metrology and spectroscopy,the complete characterization of a single ultrashort laser pulse requires accurate measurement of the offset between the electric field and the pulse envelope,namely,the carrier-envelope phase(CEP).Plenty of theoretical and experimental investigations show that accurate measurement of CEP is of special significance for fully characterizing the few-cycle laser pulses and comprehensive understanding of the field-matter interaction.Although the stereo above-threshold ionization(ATI)approach has convinced people its ability to measure the CEP with high accuracy,the characterization of the measurement accuracy and the prediction of the bound of the measurement accuracy are still absent.Fisher information,which is closely related to precision measurement,can be used to estimate the accuracy of the measured parameter.In this paper,we applied the Hellinger distance formula to extract Fisher information from the experimental data,and used the extracted Fisher information to characterize the accuracy of the scheme.On the other hand,by numerically solving the time-dependent Schrodinger equation,we calculated the photoelectron energy spectrum and momentum spectrum corresponding to CEPs in few-cycle intense laser pulses,and investigate the schemes of extracting the Fisher information of CEP based on asymmetric parameters and photoelectron momentum spectrum.The details are as follows:The first chapter briefly introduces some basic concepts involved in the measurement of CEP in strong field physics,the importance of CEP in strong field physics and the progress of its measurement.The Fisher information and the Cramer Rao lower bound(CRB)are also introduced.In the second chapter,we made attempts to extract the Fisherinformation from the measured data of CEP in stereo-ATI measurement,and compare the calculated results with the experimental results.In the first,we introduce the theoretical method of Hellinger distance formula extraction in detail.In the next,based on the measured CEP dependence of the asymmetric parameters,we explored how to accurately extract Fisher information from the experimental data.Among them,we read the phase asymmetry parameters X and Y in the original experimental date,performed numerical simulation,build a two-component measurement model,and finally emploied the Hellinger distance formula extraction method to extract the Fisher information we need.Through analysis,we concluded that the highest accuracy occurs at CEPs with value of 5?/9 or 5?/9+17?/10,which is in consistent with the conclusion of the measurement.In the third chapter,firstly,by numerically solving the time-dependent Schr?dinger equation,we calculated the energy spectra for different CEPs of few-cycle intense laser pulse,and calculated the corresponding asymmetric parameters X and Y.Based on the above results we applied definition formula and the Hellinger distance formula,respectively,to extract the Fisher information.The CEP dependence of the Fisher information behave as a sine(X)or a cosine curve(Y).The results obtained with definition formula are consistent with the results calculated with Hellinger distance method,indicating that both methods of calculating Fisher information are applicable.Secondly,We transform the photoelectron spectrum in the previous section into momentum spectrum,and the Fisher information of CEP accuracy is extracted by using Hellinger distance formula.The Fisher information corresponding to CEP theoretical calculation in the range of 0-2?is obtained,and the results of the two theoretical calculation methods are carried out Contrast.In the last chapter,we summarize the works in this thesis and prospect the future work.