THz Nonlinearity Enhancement by Phonon Polaritons in Ionic Crystals

Optical nonlinearity at the THz frequency has drawn extensive attention for its fascinating prospects. Here we show that THz nonlinearity in ionic crystals can be enhanced by orders of magnitude through phonon polaritons, which is also theoretically demonstrated by nonlinear modified Huang equations. This result shows great potential for the technologies based on THz nonlinearities, and provide a novel material modulation technique to the ionic crystals.