Giant optical nonlinearity interferences in Terahertz quantum structures

Second-order optical nonlinearities can be greatly enhanced by orders of magnitude in resonantly excited nanostructures. However, they are frequently not as heightened as predicted, limiting their exploitation in nanostructured THz nonlinear optics. Here, we show that the second-order nonlinear susceptibility can vary by orders of magnitude as a result of giant destructive interference effects. Using THz quantum-cascade-lasers as a model source to investigate interband and intersubband nonlinearities, we show that these giant interferences are a result of an interplay of the second-order nonlinear contributions of multiple light and heavy hole states. As well as of importance to engineer the resonant optical properties of nanostructures, this framework can be employed as a novel, sensitive tool to elucidate the bandstructure properties of complex materials.