Optical response of two-dimensional electron fluids beyond the kohn regime: strong nonparabolic confinement and intense laser light.

We investigate the linear and nonlinear optical response of two-dimensional interacting electron fluids confined by a strong nonparabolic potential. We show that such fluids may exhibit higher-harmonic spectra under realistic experimental conditions. Higher harmonics arise as the electrons explore anharmonicities of the confinement potential (electron-electron interactions reduce this nonlinear effect). This opens the possibility of controlling the optical functionality by engineering the confinement potential. Our results were obtained within time-dependent density-functional theory. A classical hydrodynamical model is in good agreement with the quantum-mechanical results.