Abstract
In the experiment of quantum optics, it is important to have a ultra-bright sources of temporally long, narrowband biphotons. it will be a useful tool in verifying fundamental principle in quantum mechanics, developing quantum communication technology or designing a quantum computer. In this article, I will analyze the behavior of monolithic doubly resonant biphoton source by theoretical computing and numerical simulation. More precisely, from the slow varying envelope equation of single-mode, we can get coupling equation of muti-mode. Numerical simulation can tell us the relation between the experiment parameter and the mode of photons. Finally, we compare the results of simulations and experiments.