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Ab initio theoretical investigation of the frequency comb structure and coherence in the vuvxuv regimes via highorder harmonic generation
Juan J. Carrera, SangKil Son, and ShihI Chu
Phys. Rev. A 77, 031401(R) (2008) [BibTeX][pdf]doi:10.1103/PhysRevA.77.031401
We present a fully ab initio quantum investigation of the frequency comb structure and coherence within each order of the highorder harmonic generation (HHG) spectrum in the highfrequency vuvxuv regime. The HHG spectrum driven by a train of equalspacing short laser pulses is calculated by propagating the timedependent Schrödinger equation accurately and efficiently by means of the timedependent generalized pseudospectral method. We explore the comb structure and coherence by varying the laser pulse separation τ, the number of pulses N, and the laser intensity. We find that a nested comb structure appears within each of the harmonics, ranging from the first harmonic all the way to the cutoff harmonic, and this global pattern persists regardless of the values of τ and N used. The comb structure of the harmonics originates from quantum interferences among induced dipole pulses. Finally, the frequency comb structure prevails even in the presence of appreciable ionization. Tags: TDSE,
comb laser,
strongfield,
H atom,
HHG,
KU
