Abstract
Using a nonlinear crystal, the perspective of this experiment is to construct an ultrabright source of temporally long, narrowband single biphotons through the process of spontaneous parametric down conversion. With the coating deposited on both spherical faces of the crystal, it becomes a monolithic doubly resonant parametric down-convertor without external filtering. On the other hand, the monolithic convertor becomes an optical parametric oscillator (OPO) when the pump power is above the threshold. While an optimized OPO signal implies that an ultrbright source has been constructed, optimizing an OPO signal is much easier than optimizing a single photon source. OPO obtained at high pump power is the theme of this thesis. The system was constructed initially from assembling a homemade external cavity diode laser. Some characteristics of the OPO have been featured.