Several NLO effects are particularly relevant in nanomaterials:
Second-Harmonic Generation (SHG): The process where two photons combine to form a new photon with twice the energy (and half the wavelength). Third-Harmonic Generation (THG): The generation of light with triple the frequency of the original light. Kerr Effect: A change in the refractive index of a material in response to an applied electric field. Four-Wave Mixing (FWM): A nonlinear process where interactions between different light waves produce new frequencies. Optical Parametric Amplification (OPA): Amplification of a signal using a nonlinear interaction with a pump laser.
