A Model of Terahertz Parametric Process Including Spontaneous Parametric Down-conversion

A new numerical model of terahertz parametric process is demonstrated, which takes the spontaneous parametric down-conversion into consideration by adding tens of frequency components in the coupled-wave equations. To set the values of some parameters in this model, the residual pump energy and idler spectra during spontaneous parametric down-conversion are measured experimentally for different pump energy and crystal lengths. Compared with previous models which only involve three waves, the new model is more accurate, especially when the seed power is low or the generated terahertz-wave is in the low frequency region.