光梳雷射產生銫原子同調居量捕獲之計算

Abstract

在一個三能階的系統，使用兩道雷射光，產生Lamda-type雙光子共振條件，即可發生同調居量補獲(coherent population trapping)。以銫原子為例子，所考慮的三個能階，其中兩個為基態S1/2 的兩個超精細結構，和其中一個P能階的超精細結構。所選則的能階要符合下列條件：基態的兩個能階都需能與P能階做單光子吸收，才能形成Lamda-type雙光子共振條件，這時候會發現，原子系綜會在基態產生很好的同調性，同時激發態沒有居量，原子系綜處於不會吸收光子的狀態，稱為暗態。 我們在這篇論文裡，計算使用光梳雷射在銫原子所觀察到的CPT(coherent population trapping)訊號，比較光梳雷射與鎖模脈衝雷射觀察到CPT訊號的差異的差異。我們除了典型的三能階系統外，還會考慮4能階系統，這時候考慮原子P能階中有兩個超精細結構，同時可以形成L-type雙光子共振，計算這時候所觀察到的CPT訊號,發現原先的CPT訊號被破壞。這篇論文使用數值分析的演算法為ADM(Adomian's decomposition method)法。

We calculate the phenomenon of coherent population trapping of cesium atoms that are performed by different sorts of laser, that is, continuous wave laser and femtosecond optical frequency comb laser. We also consider a four-level system, not only three-level system. Comments on the difference between the two systems. In the case of four-level system, there are two hyperfine levels of cesium P3/2 state can involve in L scheme coherent population trapping simultaneously. According to our calculation, the signal-to-noise ratio of CPT signal in the case of four levels is smaller than the case of three levels. The algorithms used in our calculation is Adomian's decomposition method.