這個實驗的願景是希望利用一塊非線性晶體，通過自發參量降頻轉換，構建一個高亮度單光子光源。此光源產生的光子相干時間長，線寬窄，對建立量子網路有很重要的意義。 我們在晶體的前後兩（球）面鍍上適當的鍍層，使得不需要像過去使用非線性晶體產生單光子時，外加光學濾波元件; 同時兩球面構成的腔，可令產生的光子共振而提升效率；這些特點令到整個系統變得簡潔而實用。晶體的前後兩個表面被打磨成適當的球面，球面上的鍍層使晶體在泵浦光的增強的時候變為一個光學參量振盪器，這使得我們可以利用優化訊號較強的光學參量振盪器間接優化單光子光源的光路架構。
本文主要探究這個實驗的第一步，構建一個可調的光學參量振盪器。我們從構建一支自製的外腔雷射開始，搭建了光學振盪器（也是以後的單光子光源）的光路，觀察並探究此光學振盪器的性質。

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.

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