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.

中文翻译：

---

太赫兹参数化过程中的非线性光学上转换：仿真与实验


我们提出了一种数值方法来模拟太赫兹（THz）参数过程中的非线性光学上转换。具体来说，我们引入了自发参量下转换（SPDC）闲频光束和上转换斯托克斯光束之间的竞争概念。我们用每个频率分量的绝对功率来模拟频谱，清楚地显示了比赛结果。通过该方法，我们从理论上解释了注入信号对SPDC闲频背景的抑制效果。我们还通过使用上转换参数检测系统对模拟进行了实验验证。我们展示了斯托克斯信号和 SPDC 闲频背景之间的竞争结果，即不同输入太赫兹能量引起的不同程度的抑制。还评估了上转换系统的实际检测能力。所有这些实验结果与理论模拟非常吻合。这项研究使人们能够全面了解上转换检测以及太赫兹参数生成和种子注入的物理原理。