本論文提出了一種基於銫原子 6S1/2 → 7S1/2 雙光子躍遷的創新光功率量測方法。通
過研究原子躍遷中的 AC­Stark 頻移，本研究為建立功率量測標準奠定了基礎。在重力
波觀測中，準確的絕對功率量測對於確定重力波事件源的距離至關重要。然而，現有
的功率量測系統因感測器老化及量子效率不一致，導致測量結果存在偏差，需頻繁進
行校正。原子躍遷提供了一種克服這些限制的方法，使光功率量測更具穩定性和可重
現性。
本研究開發了一套基於原子的光功率量測系統，整合了碘穩頻雷射、偏頻鎖定技術
以及腔體增強的雙光子吸收光譜技術。碘穩頻雷射提供了不受 AC­Stark 頻移影響的頻
率基準，偏頻鎖定則將其穩定性轉移至從屬雷射。透過利用光強度與 AC­Stark 頻移之
間的線性關係，系統可實現準確且寬量測範圍的功率量測。腔體增強設計確保光束的
波形與原子束交互區域良好定義，進一步降低不確定性。
該系統展示了 0.56 kHz/mW 的功率頻率響應度，可量測功率的解析度為 5.4 mW，
實驗可重置性為 3 kHz。目前光功率的不準度為 ∆P /P = 7 %，突顯此系統作為未來功
率校正標準基礎的潛力。

This dissertation introduces an innovative approach to optical power measurement using the
cesium 6S1/2 → 7S1/2 two­photon transition. The investigation of the AC­Stark shift in atomic
transitions serves as a foundation for developing a power measurement standard. In gravitational
wave observatories, accurate absolute power measurements are essential for determining source
distances of gravitational wave events. However, the existing power measurement systems suf­
fer from inconsistencies due to sensor aging and varying quantum efficiencies, necessitating
routine recalibrations. Atomic transitions provide a pathway to overcome these limitations by
enabling robust, reproducible, and digital optical power measurements.
The atom­based power measurement system developed in this work integrates an iodine­
stabilized laser, offset­locking technique, and cavity­enhanced two­photon absorption spec­
troscopy. The iodine­stabilized laser offers a frequency reference immune to the AC­Stark shift,
while offset­locking transfers its stability to the slave laser. By leveraging the linear relation­
ship between optical intensity and the AC­Stark shift, the system enables accurate and wide­
range power measurements. The cavity­enhanced design ensures well­defined beam profiles
and cross­sectional areas for atom­beam interactions, minimizing uncertainties.
The system demonstrates a power­frequency conversion factor of 0.56 kHz/mW, achieving
the power measurement resolution of 5.4 mW and a resettability of spectral measurements of
3 kHz. The current power measurement uncertainty is ∆P /P = 7 % under typical operating
conditions, highlighting the potential of this system as a foundation for future power calibration
standards.

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