Today, the fact that non-ionizing THz and mm wave can be used in many areas reveals the necessity of devices that can efficiently detect these waves. Compared to existing commercial detectors, cost-effective neon indicator lamps acting as glow discharge detectors (GDDs) are known to be better in speed and responsivity. In GDDs, detection occurs as a result of the interaction between radiation and plasma. Although there are many studies in the literature trying to explain this interaction, these studies are limited to qualitative explanations made as a result of the experiments and the analytical models. Since GDDs are low pressure, non-local thermal equilibrium (non-LTE) plasma lamps, the plasma in these detectors has been simulated by using the parallel 1d3v Particle in Cell/Monte Carlo Collision (PIC/MCC) code, which can be used to study the kinetic behavior of particles. The interaction between plasma and THz/mm wave have also been included to the simulation code in order to examine the effect of this interaction. The results show that not only the electrical but also the optical detection mechanism that has been recently shown using GDDs could be analyzed with this code. Therefore, in this study, the reason for the brighter glow observed as a result of plasma-THz/mm wave interaction is investigated. In this context, the effect of THz/mm wave on one of excited states responsible for the light emitted by GDD is simulated and the results are discussed.