Nonlinear terahertz conductivity spectra of charges confined in semiconductor nanostructures were calculated using a semiclassical Monte Carlo method. The confinement-induced nonlinear response per charge carrier is much stronger than the intrinsic nonlinearity of common bulk semiconductors and more than 20 times stronger than in graphene, which has been considered as a material with one of the highest terahertz nonlinearities. Moderate intensities of the terahertz radiation are thus sufficient to achieve efficient frequency mixing or high-harmonics generation. Enclosing the nanostructures into metallic nanoslits concentrates the electric field into the semiconductor and thus easily provides nonlinear terahertz signal strength comparable to the linear one.

• Received 31 July 2019
• Revised 13 May 2021
• Accepted 14 May 2021

DOI:https://doi.org/10.1103/PhysRevB.103.205426