Photon management in harmonic generation at the nanoscale

Dielectric nanoantennas have recently shown huge potential for nonlinear optics. High-refractive index nanoresonators have proved efficient second-harmonic generation (SHG) and third-harmonic generation (THG) from an optical pump beam either at visible or NIR frequencies in the static regime. In this chapter a focus about SHG in such structures is reported and after a brief historical review of SHG in AlGaAs nanostructures, we report the new promising concept of tunability. In particular, we present two innovative approaches to modulate the nonlinear emission. Firstly, we explain the possibility to modulate the SHG by using liquid crystals and lastly we discuss the thermo-optical modulation of the second-harmonic light.