雙光束耦合頻率解析光閘相位還原演算法之研究

Abstract

在本論文中，我們藉由雙光束耦合技術（spectrally resolved two-beam coupling，SRTBC）發展了一個新的相位還原演算法（phase retrieval algorithm）來計算超短脈衝雷射的振幅與相位。我們稱此量測技術為雙光束耦合頻率解析光閘（two-beam coupling frequency-resolved optical gating，TBC-FROG）。我們利用此演算法對一些典型的脈衝電場作了一些模擬計算。接著我們探討了雙光束耦合頻率解析光閘影像（TBC-FROG trace）雜訊對計算脈衝電場的影響，發現雜訊對脈衝的線性啾頻係數的影響比對脈衝寬度的影響為大。最後，我們將雙光束耦合頻率解析光閘與大家所熟知的二倍頻頻率解析光閘比較，發現雙光束耦合頻率解析光閘比二倍頻頻率解析光閘敏感，尤其是在相位變化極小的情形下更是靈敏。

In this contribution, we report the development of a new phase retrieval algorithm to extract the amplitude and phase of femtosecond laser pulses based on spectrally resolved two-beam coupling (SRTBC). This new pulse measurement method is called two-beam coupling frequency resolved optical gating (TBC-FROG). Its calculations on typical ultrashort light pulses are presented. The issue of the time and frequency sampling is discussed. We also investigate the influence of the noise in the TBC-FROG trace on the retrieved electric field. Finally, the comparison between this method and the well-known second harmonic generation FROG method (SHG-FROG) is given. TBC-FROG is found to be more sensitive than SHG-FROG in the case of pulses with a very little chirp.