在傳統的各種脈衝量測技術中，如:疊代傅立葉轉換與主成分廣義投影演算法(principal components generalized projection algorithm (PCGPA))，因顧慮到群速度不相匹配或低訊噪比等問題，因此只適合用於重建飛秒等級左右的脈衝，無法用於更短的脈衝重建。在論文中，我們利用時域上的重疊關聯成像技術便能解決之前量測技術的難題，因為此方法能以不完整的時頻譜重建出原本的脈衝。換句話說，晶體厚度(訊噪比)與群速度匹配的權衡問題已經不存在。而此優點也界定了時域與空間域重疊關聯成像的差別。此論文首次在模擬與實驗上找出脈衝寬度與所需的最小不完整時頻譜間的關係，兩者的變化呈現正相關。更重要的是，我們進一步證明只要能取得在時頻譜中的基頻頻譜中心頻率的二倍頻頻率與延遲軸的中心點，即可成功還原完整的脈衝資訊。

Conventional ultrashort optical measurement techniques such as iterative Fourier transform and principal components generalized projection algorithm (PCGPA) are suitable to characterize femtosecond pulses rather than attosecond pulses because they often suffer from several problems such as group velocity mismatch (GVM) or poor signal-to-noise ratio (SNR). Time-domain ptychography (TDP) which allowing the down-sampling and truncation in frequency and delay grid can easily eliminate these drawbacks. In other words, a thick crystal can be used to get good SNR and relax the consideration to GVM. Moreover, this feature also indicates that there is no analogy between TDP and spatial-domain ptychography. In this work, we first numerically and experimentally found that the pulse shape is strongly related to the required minimum widow size. There is a positive correlation between the required size and the test pulse duration. More importantly, a second-harmonic spectral center twice of the fundamental frequency center (Ω=2ωc) and zero delay (τ=0) is both essential to obtain the good quality reconstruction.

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