Modeling Optical Rectification In Doubly-Resonant Dielectric Nanostructures: Effective Nonlinear Response And THz Emission Control

Frequency-conversion is one of the many applications that has benefited from the rapid development of the field of nonlinear nanophotonics. In this work we theoretically study the difference-frequency generation process between two NIR pump fields in Mie-resonant nanoscatterers, which via the χ(2)(ω 3 ω 1, -ω 2) susceptibility emit a THz-signal. The key features responsible for enhancing the conversion-efficiency are disentangled and a comparison is reported between the numerical results yielded by pillars made of Al 0.18 Ga0.82 As and LiNbO3. These are complemented with a reduced effective model for the down-conversion process, together with an analysis of the radiation pattern dependence on crystal orientation.