High-Order Harmonics Generation in MoS 2 Transition Metal Dichalcogenides: Effect of Nickel and Carbon Nanotube Dopants.

The transition metal dichalcogenides have instigated a lot of interest as harmonic generators due to their exceptional nonlinear optical properties. Here, the molybdenum disulfide (MoS 2 ) molecular structures with dopants being in a plasma state are used to demonstrate the generation of intense high-order harmonics. The MoS 2 nanoflakes and nickel-doped MoS 2 nanoflakes produced stronger harmonics with higher cut-offs compared with Mo bulk and MoS 2 bulk. Conversely, the MoS 2 with nickel nanoparticles and carbon nanotubes (MoS 2 -NiCNT) produced weaker coherent XUV emissions than other materials, which is attributed to the influence of phase mismatch. The influence of heating and driving pulse intensities on the harmonic yield and cut-off energies are investigated in MoS 2 molecular structures. The enhanced coherent extreme ultraviolet emission at ~32 nm (38 eV) due to the 4p-4d resonant transitions is obtained from all aforementioned molecular structures, except for MoS 2 -NiCNT.