High-order harmonic generation in a driven two-level atom: Periodic level crossings and three-step processes

摘要: We investigate high-order harmonic generation in closed systems using the two-level atom as a simplified model. By means of windowed Fourier transform time-dependent dipole acceleration, we extract main contributions to this process within cycle driving field. show that patterns obtained can be understood by establishing parallel between and three-step In both models, is consequence process, which involves either continuum ground state, or adiabatic states Hamiltonian. The knowledge physical mechanism allows us manipulate states, consequently spectra, bichromatic Furthermore, scaling laws, establish sharp criteria for invariance quantities involved. Consequently, our results extended broader parameter range, as, instance, those characteristic solid-state strong fields.