氦原子三重態的2S至3P精密光譜量測

Precision Measurement of Helium Triplet 2S to 3P Transition

楊勝方(Sheng-Fang Yang)

指導教授 ： 王立邦

國立清華大學/理學院/物理學系/碩士(2017年)

摘要

本論文中，我們使用自製的外腔二極體雷射當作種子光源，其波長為778nm，經由一個Newport製造的Tapered amplifier放大其功率後，我們可以得到超過500mW的功率；我們把一部分的光打進一個波導式的PPLN，將778nm的雷射光倍頻成389nm的光源，然後利用此光源進行氦原子2 3S到3 3P的飽和吸收光譜；同時另一部份的光源和我們實驗室的光頻梳系統做拍頻，再利用offset lock的線路將我們的雷射鎖在光頻梳上，我們就可以精確的量測出雷射和譜線的頻率。我們得到的結果為，23S1→33P1的中心頻率是770724725.990(235) MHz，23S1→33P2的中心頻率是770724066.748(112) MHz，然而因為原子和光在低氣壓時的作用和我們預期的不一樣，所以我們還需要做更進一步的量測和理論分析，來確保中心頻率的準確性。

關鍵字

氦原子 ； 光譜 ； 三重態

並列摘要

In this paper, we used a homemade external cavity diode laser (ECDL) as our seed laser and its wavelength was 778 nm. Then, we used a commercial tapered amplifier (Newport TA-7600) to boost our power up to more than 500 mW. After the tapered amplifier, the laser beam was split into two beams. One was sent to a waveguide PPLN to double the frequency of 778 nm and the other one was beaten with the optical fiber comb system in our lab. We used the beam at 389nm to perform the saturated absorption spectroscopy and measured the transition of helium atom from 2 3S to 3 3P. The absolute frequency was measured by the fiber comb system. We used the beat frequency between the ECDL and fiber comb system and an offset lock circuit to lock our laser on fiber comb system. Therefore, we could precisely know the absolute frequency of our laser and the targeted transition. The results of the transition frequencies were as follow: 23S1→33P1 f=770724725.990(235) MHz and 23S1→33P2 f=770724066.748(112) MHz. The precision of the results reached 〖10〗^(-10), but the accuracy of the absolute frequency had to be studied again and carefully because there were some effects between atoms and light, which could shift the center frequency of the transition.

並列關鍵字

Helium ； Spectroscopy ； Triplet

參考文獻

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