本論文使用冷銣原子研究基於電磁波引發透明下的反向四波混頻，光波長自780奈米轉為795奈米。根據理論預測，在光學密度39與85時，分別有近75%與90%之轉換效率。我們分別以驅動光拉比頻率與雙光子調變作為操縱變因進行兩種實驗，然而我們實驗所得之轉換效率皆低於理論所預測，並且實驗結果之行為與理論曲線不符，我們推測此現象與相位不匹配以及雙光子調變間的補償有關，因此若我們要實現轉換效率高於90%的量子轉頻器尚有課題需克服。

In this thesis, we use cold rubidium atoms to study backward four-wave mix-ing (BFWM) based on electromagnetically induced transparency (EIT). The wavel-ength of the light is conversed from 780 nm to 795nm.

Based on the theoretical model, under optical density (OD) 39 and 85, the e-fficiency of the conversion can reach around 75% and 90% respectively. We con-duct two kinds of experiments, one is that we change the Rabi frequency of the driving light, and the other is we change the two phpton detuning. However, bothof the efficiency we observed are lower than that of predicted by the model. Plu-s, the results do not behave like the thereotical curves. We surmise that this is d-ue to the compensation between two photon detuning and phase mismatch. Finall-y, if we want to achieve efficiency 90%, there are still some issues need to be
considered.

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