Laser waveform control of extreme ultraviolet high harmonics from solids

TLDR

Solid-state high-harmonic sources promise compact, high‑repetition‑rate attosecond light emitters, yet their time structure must be characterized at the sub‑cycle level. We use strong two‑cycle laser pulses to directly control the time‑dependent nonlinear current in single‑crystal MgO, generating extreme‑ultraviolet harmonics. The harmonics are delayed relative to each other, producing an atto‑chirp whose magnitude depends on laser field strength, laying the groundwork for attosecond pulse metrology and sub‑cycle dynamics studies in solids.

Abstract

Solid-state high-harmonic sources offer the possibility of compact, high-repetition-rate attosecond light emitters. However, the time structure of high harmonics must be characterized at the sub-cycle level. We use strong two-cycle laser pulses to directly control the time-dependent nonlinear current in single-crystal MgO, leading to the generation of extreme ultraviolet harmonics. We find that harmonics are delayed with respect to each other, yielding an atto-chirp, the value of which depends on the laser field strength. Our results provide the foundation for attosecond pulse metrology based on solid-state harmonics and a new approach to studying sub-cycle dynamics in solids.