Synchronized Generation And Coherent Modulation On High Harmonics And Terahertz Spectroscopy From Aligned Molecules

The interaction between strong laser fields and atoms or molecules may coherently emit high harmonics from extreme ultraviolet to soft X-ray spectral range,as well as the millimeter to sub-millimeter terahertz wave.Synchronizing high harmonic and terahertz spectroscopy(HATS)is demonstrated as a new tool for peering and manipulating the structures and dynamics of atoms or molecules.Thanks to the spectral range covering frequencies and scales of more than 5 orders of magnitudes,HATS will deepen the understandings of electronic dynamics within strong field process,as well as the realization of the in site manipulations.Firstly,we briefly review the strong field interactions between laser and atoms,and introduce some new methods on discovering the molecular structures and dynamics.Secondly,the experimental setup are presented for HATS from aligned molecules,namely the laser system,the preparation of molecules,the transient alignment and the technical details on the HATS detection.Thirdly,taking advantages of the HATS detection,we study the highest occupied molecular orbital(HOMO)of nitrogen and the multi-channel dynamics of carbon dioxide.Finally,we draw a conclusion by summarizing our findings and proposing the potential applications about our HATS methods.Three innovative ideas are raised within this thesis:(1)The alignment-angle dependent THz yields can be applied to calibrate the angular ionization rates of aligned molecules,which is established on nitrogen and carbon dioxide.This is an all-optical,coherent approach for characterizing ionization rates,which is a supplement to the current ionization methods based on the electrons or ions detections.Meanwhile,this may help the understanding of ionization process under strong field interactions.(2)The HATS from aligned molecules has been applied to reveal the angular differential photo-recombination/photo-ionization cross section of the HOMO of nitrogen.The combination of the emissions at two different wavelengthes may provide a better view on molecular structure by an all-optical way within one run of measurement.(3)The HATS technique is extended to two dimensions by varying the dual-color relative phase and the alignment angles.The contributions of inner orbitals(HOMO-1,HOMO-2)on high harmonic emissions are identified and applied to in site manipulate the attosecond pulse trains.