許朋

鐿原子光頻標(biāo)中泵浦光特性的研究

許朋

（皖北衛(wèi)生職業(yè)學(xué)院，宿州 234000）

鐿原子光頻標(biāo)中泵浦光參數(shù)的優(yōu)化可以提高鐘頻率穩(wěn)定度性能。通過分析鐿原子能級(jí)分布的特點(diǎn)，建立了能級(jí)躍遷速率方程。采用數(shù)值計(jì)算方法求解速率方程，獲得了泵浦時(shí)間與649 nm、770 nm、1388 nm泵浦光的光強(qiáng)和失諧的關(guān)系。比較了兩種泵浦方法的效果，分析了泵浦時(shí)間的改變對(duì)鐘頻率穩(wěn)定度性能的影響。理論計(jì)算的結(jié)果為實(shí)驗(yàn)確定泵浦光的光強(qiáng)、泵浦時(shí)間提供了重要的參考。

鐿原子光頻標(biāo)；速率方程；泵浦光

0 引言

1 泵浦方案一分析

圖1 鐿原子的能級(jí)圖

649 nm和770 nm泵浦光共同作用下，處于不同能級(jí)的原子數(shù)的變化方程如下[12-14]

圖3 能級(jí)的原子數(shù)達(dá)到10 000時(shí)需要的泵浦時(shí)間t隨649 nm和770 nm激光光強(qiáng)的變化

從圖3可知，在649 nm激光光強(qiáng)> 5且770 nm激光光強(qiáng)> 1區(qū)域，泵浦時(shí)間不超過30 μs。綜合計(jì)算的結(jié)果，一定條件下，我們?nèi)?49 nm激光光強(qiáng)= 5，770 nm激光光強(qiáng)= 1。

圖4 能級(jí)的原子數(shù)達(dá)到10 000時(shí)需要的泵浦時(shí)間t隨激光失諧g和h的變化

圖5 能級(jí)的原子數(shù)達(dá)到10 000時(shí)需要的泵浦時(shí)間t隨649 nm和770 nm激光失諧的變化

從圖5可知，649 nm激光和770 nm激光的失諧都在-400 MHz以內(nèi)時(shí)，泵浦時(shí)間不超過10 ms。一般情況下，649 nm激光的失諧在-200 MHz以內(nèi)且770 nm激光的失諧在-400 MHz以內(nèi)時(shí)，泵浦時(shí)間不超過3 ms。隨著649 nm激光失諧的增大，泵浦時(shí)間顯著的變大。

最后分析一下649 nm和770 nm激光頻率漂移引起的泵浦時(shí)間的變化d/MHz。假定649 nm和770 nm激光都偏離其對(duì)應(yīng)躍遷的共振頻率200 MHz，在這一點(diǎn)d/MHz的數(shù)值為：649 nm為21.9 μs/MHz，770 nm為0.1 μs/MHz?？芍?，泵浦時(shí)間隨649 nm激光頻率漂移變化較大。

2 泵浦方案二分析

圖6 1 388 nm激光作為泵浦光時(shí)，鐿原子的能級(jí)圖

圖7 能級(jí)的原子數(shù)達(dá)到穩(wěn)態(tài)時(shí)需要的泵浦時(shí)間t隨1 388 nm激光光強(qiáng)s的變化

從圖8可知，1 388 nm激光失諧從0 MHz增加到-50 MHz時(shí)，從0.2 ms增加到21 ms。因此，1 388 nm激光的失諧不能較大，頻率漂移要比較小，否則需要很長(zhǎng)的時(shí)間才能完成原子的泵浦。

圖8 能級(jí)的原子數(shù)達(dá)到穩(wěn)態(tài)時(shí)需要的泵浦時(shí)間t隨1 388 nm激光失諧ω的變化

3 討論

4 總結(jié)

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The research of the characteristics of pump light in ytterbium atomic optical frequency standard

XU Peng

(North Anhui Health Vocational College, Suzhou 234000, China)

The optimization of the pump light parameters in the ytterbium atomic optical frequency standard can improve the clock frequency stability performance.By analyzing the characteristics of the energy level distribution of ytterbium atom, the energy level transition rate equation was established.The numerical calculation method was used to solve the rate equation, and the relationship between the pumping time and the intensity and detuning of the pump light at 649 nm, 770nm and 1 388 nm was obtained.The effects of the two pumping methods were compared, and the effect of changes in pumping time on the performance of clock frequency stability was analyzed.The results from our theoretical calculation provide an important reference for the experiment to determine the pump light intensity and pumping time.

ytterbium atomic optical frequency standard; rate equation; pump light

10.13875/j.issn.1674-0637.2021-02-0085-07

許朋. 鐿原子光頻標(biāo)中泵浦光特性的研究[J]. 時(shí)間頻率學(xué)報(bào), 2021, 44(2): 85-91.

2020-10-15；

2020-12-05