Anomalous ellipticity dependence of high-order harmonic generation

Generation of below-threshold even harmonics by a stretchedH2+molecular ion in intense linearly and circularly polarized laser fields

“…Several theoretical and experimental studies [2][3][4], particularly in elliptically polarized field [5], for BTH have been performed. For a certain order of BTH, abnormal ellipticity dependence of the harmonic yield was observed [6]. However, the mechanism of the BTH generation is still not understood very well and remains an open question.…”

Static-Electric-Field-Induced Polarization Effects in Harmonic Generation

“…Antoine et al [5] confirmed such behavior, finding that the rotation angles and ellipticities of the harmonics strongly depend on their position in the spectrum, but that the ellipticities of the harmonics remain smaller than that of the driving laser. Other experiments have found unusual polarization characteristics for particular harmonics [6]. Theorists, meanwhile, have found that prediction of harmonic polarization provides a stringent test of models and methods [3,7,8].…”

Angular Dependence of High-order Harmonic Generation from Nonadiabatically Aligned Molecules

“…In the calculation for N 2 , we used the rotational constant B = 1.99 cm -1 , from which a revival period T rev = 1/(2Bc) is calculated to be 8.3 ps, and a constant value of p 2 so as to fit the result to the experimental. The rotational temperature was set at T rot = 100 K, since this value reproduced the frequency spectrum of S (19) (Δt) having the peak at the same J as that in the experimental. As shown in Fig.1, the leading term p 2 <<cos 2 θ>>(Δt) in Eq.…”

“…The n-th harmonic radiation was detected by an electron multiplier mounted on a vacuum ultraviolet monochromator, and the signal was processed by a boxcar averager, converted to the digital signal with an A/D converter and stored on a personal computer. The probe pulse polarization was fixed to the direction along the entrance slit of the monochromator to maintain a constant diffraction efficiency, 19) while the pump polarization was rotated. Figure 1 shows the time-dependent 19th harmonic signal observed for N 2 as a function of Δt for α = 0˚ and the 19th harmonic signal S (19) (Δt) calculated by the leading term p 2 <<cos 2 θ>>(Δt) in Eq.…”

“…The probe pulse polarization was fixed to the direction along the entrance slit of the monochromator to maintain a constant diffraction efficiency, 19) while the pump polarization was rotated. Figure 1 shows the time-dependent 19th harmonic signal observed for N 2 as a function of Δt for α = 0˚ and the 19th harmonic signal S (19) (Δt) calculated by the leading term p 2 <<cos 2 θ>>(Δt) in Eq. (3) under the same condition as the experiment.…”