In the interaction of intense infrared lasers with atoms/molecules, an ionized election is accelerated by the laser field, and revisits the parent ion. High energy electrons are generated after rescattering with the ion, or alternatively, harmonic photons are emitted as attosecond bursts after electron-ion recombination. However, the validity of the picture requires verification in condensed-phase targets.

This study discusses the behavior of nanoclusters and semiconductors under intense femtosecond laser fields. In the laser interaction with nanoclusters, photoelectron and charged ion emission are investigated at various driving laser wavelengths. In the study of photoelectrons, we show that the laser-field-driven rescattering picture is still valid in nanoclusters after adaptions. With the help of tunable laser wavelength, we observe an extension of cutoff energy and discover its universal scaling with the cluster size and driving wavelength. On the other hand, a wavelength-dependent ion emission is observed, which sheds light on the underlying cluster dynamics. In addition, the ion emission is managed to be controlled with a tailored pulse.

In the laser interaction with semiconductors, the high harmonic photon emission driven by mid-infrared lasers are measured, which comes from distinct mechanisms from atoms/molecules. The roles of photocarrier density and driving wavelength are explored, which not only convey the information of underlying mechanisms, but also suggest approaches to optimize the harmonic generation conditions for future table-top attosecond burst generation. Moreover, a two-color beam is applied to drive the harmonic emission from solids and an enhanced frequency-upconversion efficiency is observed.