Nonlinear Optical Up-Conversion in Terahertz Parametric Process: Simulation and Experiment

We present a numerical method to model the nonlinear optical up-conversion in the terahertz (THz) parametric process. Specifically, we introduce the concept of competition between the spontaneous parametric down-conversion (SPDC) idler beam and the up-converted Stokes beam. We simulate the spectra with the absolute power of each frequency component that clearly shows the competition result. By this method, we theoretically explain the suppression effect of injected signal on the SPDC idler background. We also verify the simulation experimentally by using an up-conversion parametric detection system. We show the competition result between the Stokes signal and SPDC idler background, the different levels of suppression caused by different input THz energy. The actual detection ability of the up-conversion system is also evaluated. All these experimental results are in good agreement with theoretical simulations. This research enables a comprehensive understanding of the physics of the up-conversion detection as well as the THz parametric generation and the seed injection.