本論文展示一套基於冷銣原子鑽石型能階結構的高效率通訊頻率轉換系統，成功實現將可見光（795 奈米）轉換至通訊波段（1367 奈米）。相較於傳統的雙Λ型系統，本研究著重於在轉換效率與傳輸損耗之間取得最佳平衡，最終於光學密度分別為 75 與 110 的條件下，達成 66% 與 80% 的轉換效率，超越原子系統中先前報導的所有成果。為優化四波混頻（FWM）條件，本研究系統性地探討了內部的 V 型與級聯型電磁誘發透明（EIT）譜特性。研究亦深入分析耦合光與驅動光的失諧量，以及光學密度對轉換效率的影響，進而建立完整的理論模型與參數優化流程。實驗結果在整體趨勢上與理論預測一致，展現本系統作為一個高效頻率轉換介面的可行性。雖然本研究使用的是相干光場，先前的理論研究已指出，在轉換過程中可高保真地保留量子態，突顯鑽石型原子四波混頻於長距離光纖量子通訊中的應用潛力。

This thesis demonstrates a high-efficiency telecom frequency conversion system based on a diamond-type energy-level configuration in a cold rubidium atomic ensemble, achieving conversion from visible light (795 nm) to the telecommunication band (1367 nm). Compared to conventional double-Λ systems, this work emphasizes an optimal trade-off between conversion efficiency and transmission loss, ultimately achieving conversion efficiencies of 66% and 80% at optical densities of 75 and 110, respectively. These results surpass all previously reported values in atomic systems. A systematic investigation of the underlying V-type and cascade-type electromagnetically induced transparency (EIT) spectra is carried out to guide the optimization of the four-wave mixing (FWM) conditions. The effects of coupling and driving field detunings, as well as optical density, on the conversion efficiency are thoroughly analyzed, leading to the development of a complete theoretical model and parameter optimization procedure. The experimental results show good agreement with theoretical predictions in terms of overall trends, demonstrating the feasibility of this system as an efficient frequency conversion interface. Although this study is based on coherent light fields, previous theoretical work indicates that quantum states can be preserved with high fidelity during the conversion process, highlighting the potential of diamond-type atomic FWM for long-distance fiber-based quantum communication.

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