High-efficiency high-order harmonic generation without tunneling - art. no. 013410

High-order harmonic emission is calculated for a highly charged ion exposed to an ultra-intense laser field with an intensity near saturation. Low-ord er harmonics having an energy lower than the ionization potential I-p are e mitted with extremely high efficiency. In contrast to their usual behavior, the low-order harmonics may exhibit a plateau that is amenable to a classi cal mechanism or a resonancelike maximum, depending on the shape of the bin ding potential. Tunneling is not involved.