In THG, the nonlinear interaction of intense electromagnetic fields with a material's electronic structure results in the conversion of light at one frequency to light at a higher frequency. This phenomenon occurs due to the material's third-order nonlinear susceptibility (χ^(3)). Materials with a high χ^(3) are especially effective for THG. The efficiency of THG depends on the intensity of the incident light, the phase matching conditions, and the inherent properties of the material.
