Emission spectrum and localization of electrons in quantum-well systems induced by a strong laser field

We analytically solved the problem of a two-level system in a strong time-dependent electric field. We used parameters characteristic of an electron in a double-well heterostructure. The frequency and amplitude of the low-frequency mode were determined for arbitrary initial conditions. We show that low-frequency generation with a strong amplitude can be obtained even for excitation from the ground state (optical initial condition). For the case of the tunneling initial condition, split even harmonics of the laser frequency dominate the spectrum of the electron, while odd harmonics dominate for the optical initial condition.