10.6084/m9.figshare.1012236.v1 Di Zhao Di Zhao Fu-li Li Fu-li Li Shih-I Chu Shih-I Chu (a) Quasienergies and (b) time-averaged transition probabilities as a function of the intensity of the cavity-mode field IOP Publishing 2013 femtosecond enhancement cavity intensity cep 20 fs FWHM repetition frequency 10 THz HHG power spectra multiphoton resonance processes multiphoton resonance dynamics laser fields Atomic Physics Molecular Physics 2013-07-05 00:00:00 Figure https://iop.figshare.com/articles/figure/_a_Quasienergies_and_b_time_averaged_transition_probabilities_as_a_function_of_the_intensity_of_the_/1012236 <p><strong>Figure 4.</strong> (a) Quasienergies and (b) time-averaged transition probabilities as a function of the intensity of the cavity-mode field. The resonance position is at 1.489 <b>×</b> 10<sup>11</sup> W cm<sup>−2</sup>. (c) The enhancement of HHG power spectra by tuning the intensity of the cavity-mode field. For clarity, HHG peaks of the comb structure are connected by a line. The energy separation is fixed at ω<sub>αβ</sub> = 0.17 au. The CEP shift is fixed at Δ = 0.4385 <b>×</b> 2π. The parameters of the frequency-comb field are peak intensity 1 <b>×</b> 10<sup>14</sup> W cm<sup>−2</sup>, carrier frequency 563.5 THz and repetition frequency 10 THz of 20 fs FWHM Gaussian pulses. The carrier frequency of the cavity-mode field is 10 THz.</p> <p><strong>Abstract</strong></p> <p>We present a theoretical investigation of the multiphoton resonance dynamics driven by intense frequency-comb and cavity-mode fields inside a femtosecond enhancement cavity (fsEC). The many-mode Floquet theorem is employed to provide a nonperturbative and exact treatment of the interaction between a quantum system and laser fields. The quasienergy structure driven by the frequency-comb laser field is modified by coupling the cavity-mode field and the multiphoton resonance processes between modified quasienergy states, resulting in the generation of even-order harmonics. The high-order harmonic generation (HHG) from a two-level system driven by the laser fields can be coherently controlled by tuning the laser parameters. In particular, the tuning intensity of the cavity-mode field allows one to coherently control the HHG power spectra without changing the absolute positions of comb frequencies.</p>