本論文中我們利用脈衝整型系統產生脈衝串並使用經驗模態分解極短時傅立葉轉換解析兆赫波輻射訊號。
利用脈衝整型系統調變光的振幅和相位，提供脈衝串時間延遲所需要的振幅以及相位，相較於過往的脈衝串產生方式，例如使用多麥克森干涉儀、雙折射晶體以及chirp mixing等方法，使用脈衝整型系統可以提升延遲時間的穩定度，在時間延遲和脈衝根數的調變也較為簡易。我們也預期將可利用此方法在窄頻可調兆赫波產生上，也能得到更好的效果。
過往在分析兆赫波輻射訊號高頻展產生時間是直接藉由直接觀察兆赫波時域訊號找出高頻產訊號生時間，但是當高頻訊號發生在訊號極大值附近時則無法直接觀察出產生時間。因此需要新的訊號分析方法，一般使用短時傅立葉轉換可以得到訊號中頻率對時間的關係，然而為了兼顧時間和頻率解析度，短時傅立葉轉換在分析頻率間距不同的模態時將採用不同的時間窗口，不同的時間窗口大小將會得到不同的強度對時間關係，進而造成分析上的誤差，因此我們透過經驗模態分解將兆赫波訊號拆解成各個本質模態函數，將訊號中各個模態分解到不同的本質模態函數中將可以解決不同短時傅立葉轉換中不同時間窗口所遇到的問題。我們分析各個本質模態函數的頻率找出包含高頻訊號的本質模態函數，透過短時傅立葉轉換得到本質模態函數的時頻圖，成功解析出高頻訊號產生時間。

In this thesis we use pulse shaping system to generate pulse train. Using empirical mode decomposition(EMD) and short-time Fourier transform(STFT) to analyze the signal of terahertz radiation.
we use pulse shaping system to modulate the amplitude and phase of light which provide for pulse train generation. Compare with other method, first, our method will improve the stability of time delay control. Second this method is easier to control the time delay and number of pulse in the pulse train.
In the past, people find the occur time of high frequency by observed the time domain of terahertz radiation directly, but if the occur time near the time of the peak power of terahertz radiation, we can’t find out the occur time of high frequency. Using STFT can find out the relationship between intensity and time, but if the modes in signal have different width of frequency STFT have to use different time window to get the best frequency resolution and time resolution. However the time window with different width will have different frequency resolution, and the relationship between intensity and time will change with different frequency resolution, therefore using different frequency resolution will get different result, so we need a new signal analysis method. To solve this problem we use EMD to decompose different mode in the signal of terahertz radiation into different intrinsic mode function(IMF), and analyze the signal of terahertz by STFT to find the occur time of high frequency of terahertz radiation. Because the modes are separated in to different IMF, we can use STFT with the same time window. We expect this method applied to narrow-band frequency-tunable THz wave generation will be better.

論文審定書……………………………………………………...……...………………. i
誌謝…………………………………………………………….……...………………..iii
摘要………………………………………………………….... ………….….. ….iv
Abstract………………………………………..………………...……………...…. ….v
圖次……………………………………………………………...…………………….viii
表次……………………………………………………………………………………..xi
Chapter 1 緒論…………………………………….……………………………………1
Chapter 2 兆赫波輻射、脈衝量測、脈衝整形、訊號分析簡介…………………….6
2-1 兆赫波輻射簡介……………………………………………………....7
2-2 脈衝量測方法簡介………………………………………………..………..10
2-3 脈衝整型原理與脈衝整型系統……………………………………………13
2-4 短時傅立葉轉換……………………………………………..……………..22
2-5 經驗模態分解………………………………………………..……………..25
Chapter 3 脈衝串產生……………………………………………………..28
3-1 脈衝串簡介……………….…………………………………………..29
3-2 文獻回顧與理論分析………………………………………………..30
3-3 利用脈衝整型系統實現Mixing chirped optical pulses………..35
3-4 脈衝整型系統產生脈衝串理論與模擬…………………….…………..40
3-5 脈衝串產生實驗與討論………………………………..……………..46
3-6 總結………………………………………………………………………….53
Ch a p t e r 4 短時傅立葉轉換時域分析…………………………………. .54
4-1 短時傅立葉轉換分析wurtzite InN 的dephasing time…………………55
4-2 短時傅立葉轉換分析兆赫波訊號………………………………………..59
4-3 總結……………………………………………..………………………..65
Ch a p t e r 5 經驗模態分解時域分析……………………………………. .66
5-1 經驗模態分解不同頻率組合訊號應用之模擬…………….………..67
5-2 經驗模態分解搭配短時傅立葉轉換分析wurtzite InN 的dephasing
t ime……………………………………………………………………. . .77
5 - 3 經驗模態分解搭配短時傅立葉轉換分析兆赫波輻射………. . 8 3
vii
5 - 4 總結……………………………………………………………. . 9 0
Ch a p t e r 6 結論與未來工作……………………………………………. .92
參考文獻……………………………………………………….…………. 9 4

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