High-order Harmonic Generation from the van der Waals Layered Heterostructure Copper Indium Thiophosphate

Copper indium thiophosphate, CuInP
2
S
6
(CIPS), has unique properties including van der Waals layered structure and strong room temperature ferroelectricity. Here, we study high-order harmonic generation driven by mid-infrared pulses in CIPS, observing intense emission up to the 9th harmonic, which lies above the band gap.