本論文中，新型脈衝整型技術與高效率寬頻兆赫波的產生機制被提出與討論。首先，我們提出利用相位及振幅的調變去得到多脈衝串，脈衝之個數相較於過往之技術無偶數多脈衝輸出之限制，同時，其個別的脈衝寬度對啾頻影響的擁有相同的行為。其次，我們試圖透過激發光源的改良與理論上的計算探討兆赫輻射增強的可能方法：在激發光源方面，我們調變出多脈衝串並應用於窄頻兆赫輻射增強；在理論計算上，我們利用Drude-Lorentz model說明色散與雙光子吸收效應對光致電流之影響，也提出雙光子吸收在光導天線產生兆赫波輻射中的角色，我們突破了光導天線吸收飽和之極限，成功利用光致電流驗證雙光子吸收效應。在實驗上，透過16飛秒光脈衝激發，我們首次觀察到光電流對激發功率依存性具有非線性的特性，另外，在輻射兆赫波上，我們也觀察到達到兆赫波峰值有再次提升進而倍數增加的現象。

In this thesis, a novel method for multi-pulse with equal chirp characteristics and more efficient THz generation through two photon absorption (TPA) are investigated and demonstrated. These are all the first time, for our best knowledge, odd multi-pulses generation and innovative approach for efficient THz through TPA are proposed and studied.
By modulating the amplitude and phase of the spatial light modulator with the pulse shaper, the number of multi-pulses can be adjustable without the limitation of even number only. Meanwhile, the chirp properties of the generated pulses are with the same characteristics and tunable also. For the case with bandwidth of 10nm, the generated multi-pulses with equal chirps varying from -20000fs^2 to 20000fs^2 are demonstrated and the results have a good agreement with the theoretical estimation. We also discuss the number of the multi-pulses and inequalities of the amplitude of the pulses are limited by the spectral resolution of SLM within the pulse shaper.
Regarding to efficient THz radiation, it can be generated more efficiently from a low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) antenna by taking into account the TPA induced photo-carrier in the photoconductor. A rate-equation-based approach using the Drude-Lorentz model taking into account the band-diagram of LT-GaAs is used for the theoretical analysis. The super-linear power dependent photocurrent clarifies the role of TPA. Previously unnoticed THz pulse features and anomalously increasing THz radiation power rather than saturation were observed. These are in good agreement with the theoretical predictions.

摘要-----------------------------------------------------------iii
Abstract------------------------------------------------------iv
誌謝-----------------------------------------------------------v
圖次-----------------------------------------------------------vii
表次-----------------------------------------------------------x
第一章、緒論-----------------------------------------------1
第二章、新型脈衝整形技術-----------------------------3
2-1、脈衝整形系統----------------------------------------3
2-2、脈衝特性量測----------------------------------------5
2-3、相位凍結演算法-------------------------------------8
2-4、相位及振幅調變法理論模擬---------------------12
2-5、相位及振幅調變法實驗數據---------------------15
2-6、結論---------------------------------------------------20
第三章、窄頻兆赫波產生-------------------------------21
3-1、兆赫波時域解析光譜系統------------------------21
3-2、脈衝串激發光導天線產生窄頻兆赫波---------25
3-3、Gerchberg-Saxton 演算法----------------------27
3-4、可調式窄頻兆赫波---------------------------------31
3-5、結論---------------------------------------------------34
第四章、雙光子吸收效應-------------------------------35
4-1、光導天線理論模擬---------------------------------35
4-2、雙光子吸收效應對載子產生率之影響---------42
4-3、雙光子吸收對輻射兆赫波影響------------------46
4-4、結論---------------------------------------------------48
第五章、結論與未來展望-------------------------------49
5-1、結論---------------------------------------------------49
5-2、未來展望---------------------------------------------50
參考資料----------------------------------------------------52

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