Orientation and Ellipticity Dependence of High-order Harmonic Generation in Nanowires

Abstract

Abstract It has been predicted that high-order harmonic generation (HHG) in nanowires has the potential to scale up photon energy and harmonic yield. However, studies on HHG in nanowires are still theoretical and no relevant experimental results have been reported as yet. Our experimental observation of the high-order harmonic in cadmium sulfide nanowires (CdS NWs) excited by a mid-infrared laser is, to our knowledge, the first such study, and it verifies some of the theoretical results. Our experimental results show that the observed harmonics are strongest when a pump laser is parallel to the nanowires. Therefore, the theoretical prediction that harmonics are strongest under the nanowires parallel to the laser field is confirmed experimentally; this can be used to determine the orientation of the nanowire. In addition, harmonics are sensitive to the variation of pump light ellipticities. This orientation dependence opens new opportunities to access ultrafast and strong-field physics of nanowires.