實驗上在室溫下利用單顆羧基化硒化鎘/硫化鋅量子點(carboxyl CdSe/ZnS quantum dot)作為單光子源，得到輻射壽命(radiative lifetime)長至100ns左右的螢光[1]，並基於這種時間上足夠長的螢光特性，利用聲光調變器(acoustic-optic modulator, AOM)控制量子點(quantum dot, QD)所放出的單光子波包在時間(空間)上的強度，以改變波包的形狀，得到方波與三角波兩種異於原先的放光形式。
另外使用聲光調變器降低量子點放光初期數十奈秒內的光強度，並且測量其在二階相干性(second-order correlation)上的表現，成功地發現消除每次量子點在放光初期數十奈秒的螢光後，單顆量子點的螢光更接近完美的單光子，g^((2)) (0)從原先的0.06最低降至0.02，並且趨於定值。接著再直接分析量子點的螢光在時間上的分佈，以簡單的模型來分析經過調變後的量子點螢光在雙激子(biexciton)數量上的變化，得到了與實驗測得的二階相關函數(second-order correlation function)有相同的變化趨勢，成功地驗證我們對於單光子純化上的理解。

In our experiment, we used single carboxyl CdSe/ZnS quantum dots as a single photon source to generate single photon wave packet with a temporal width of 100ns in room temperature. Base on this characteristic, we used acoustic-optic modulator(AOM) to modulate the amplitude and shape of the single photon wave packet in the time domain. We obtained square shape and triangle shape wave packets.
In the other part of the experiment, we suppressed the intensity of QD fluorescence in the first tens of nanoseconds, and then measured the second-order intensity correlation g^((2)) (τ) of the modulated wave packet. We successfully purified the modulated single photons. The value of g^((2)) (0) dropped to 0.02, being 33% of its original value, and became a constant value. Moreover, we analyzed the distribution of QD fluorescence in the time domain to build a simple model to obtain the change of amount of biexciton in QD fluorescence. The analysis and our experimental observation are in good agreement, proving the principle of purifying single photons.

摘要……………………………………………………………………………...…………i
Abstract………………………………………………………………………………...….ii
致謝…………………………………………………………………………………….....iii
圖表目錄…………………………………………………………...……………………..vi
第一章 實驗動機………………………………………………………………………....1
第二章 實驗原理………………………………………………………………………....3
2.1共軛焦顯微鏡(Confocal microscope)………………………………………..3
2.2聲光調變器(Acousto-Optic Modulator, AOM)…………………….………..4
2.3量子點(Quantum Dot, QD)………………………………………..…………7
2.3.1 簡介………………………………………………………………..7
2.3.2 單光子機制………………………………………………………..8
2.3.3 雙激子(Biexciton)…………………………………………….….12
2.3.4 溫度影響………………………………………………………....14
2.3.5 共振激發&非共振激發…………………….…………….….…..16
2.4 光子反聚束效應….....………………..………………………….…..…….20
2.4.1 二階相關函數………...……………………………………….....18
2.4.2 連續波激發&脈衝激發………….………………………………23
第三章 實驗架設…………………………………………………………………….….26
3.1 架設概述…………………………………………………………………….26
3.2 單光子光源區………………………………………………………….……27
3.2.1 量子點樣品…………………………………..…………...……….27
3.2.2 激發與放光.. ………………………………….…………..………28
3.3 波函數調變區……………………………………………………….………30
3.3.1 聲光調變器……….……………………………………….………30
3.3.2 漢勃雷-布朗和特威斯干涉儀……………………….……………32
第四章 結果與分析……………………………………………………………………..34
4.1 單顆量子點基本量測…………………………………………….…………34
4.1.1 架設效率……………………………………………….………….34
4.1.2 量子點分佈情形………………………………….……………….34
4.1.3 螢光在時間上的變化……………………………….…………….36
4.1.4 輻射壽命量測…………..………………………...……………….38
4.2 單光子波形調變…………………………………………………………….40
4.3 單光子純化………………………………………………………………….42
第五章 結論…………………………………………………….…….…………………54
參考文獻…………………………………………………………………………………55

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