ИСТИНА

Nowadays topological insulators are considered as extremely promising materials for terahertz photonics. The outstanding properties of massless electrons in surface states, due to their topological protection against backscattering, lead to huge mobility values. High nonlinear properties in the visible and terahertz frequency ranges make topological insulators one of the best nonlinear materials for generating the high harmonics. In this work, we present and analyze the results on the generation of the third terahertz harmonic in topological insulators with a chalcogen-ordered tetradymite structure. An analysis of the experimental results indicates the possibility of obtaining higher conversion efficiency to the third harmonic in topological insulator than even in graphene. A consistent kinetic theory of third harmonic generation in topological insulators has been developed. The generation of terahertz radiation in a photoconductive antenna based on a thin film of topological insulator is experimentally demonstrated and numerically calculated.