被動鎖模鈦藍寶石雷射時序紊亂度的抑制與量測上的研究

Abstract

在本論文中，我們首次報導以皮秒電脈衝偏壓之光導開關作為諧波混頻器的光電式鎖相迴路，進行被動鎖模鈦藍寶石時序紊亂度抑制及量測的研究。在時序紊亂度的抑制上，我們利用皮秒電脈衝試著做更高倍諧頻的鎖定，使時序紊亂夜更為降低。量測上我們在時域上作直接的相位偵測與傳統頻譜量測計算時序紊亂比較。 實驗發現，以扭曲量子井飽和吸收體啟動鎖模機制的被動鎖模鈦藍寶石雷射在未回授控制腔長時，最佳的均方根時序紊亂度為7.24ps。利用光電式鎖相迴路抑制時序紊亂度，以正弦波微波電訊號鎖定雷射的第11倍諧頻，可有效降低雷射的均方根時序紊亂度，以傳統頻譜量測計算的時序紊亂度為1.56ps。使用1GHz梳形波產生電脈衝和光脈衝混頻，鎖定雷射的第11倍、第22倍、第33倍和第45倍諧頻，則可降低均方根時序紊亂度分別為1.36ps、1.26ps、0.94ps和1.33ps。 我們設計了一個電路利用在時域上直接做相位偵測來計算時序紊亂度，同樣使用1GHz梳形波產生電脈衝和光脈衝混頻，鎖定雷射的第22倍。第33倍和第45倍諧頻可降低時序紊亂度分別為524fs、351fs和493fs。

In this thesis, we demonstrate a new stabllization method based on an optoelectronic harmonic mixer (OEHM) biased by picosecond electrical pulse in a phase-locked loop to reduce and measure the timing jitter of the passively mode-locked Ti: sapphire laer. We stabilize the laser by intermixing harmonics of the electrical pulse with higher harmonics of the laser pulse train. We also demonstrated a new method which detects the phase error signal directly for computation of the r.m.s. timing jitter. The results are in good agreement with the conventional phase noise spectra measurements. The best r.m.s timing jitter for the freee running Ti: sapphire/SSBR laser is 7.24ps. With an optoelectronic phaselocked loop (OEPLL) and intermixing higher harmonics of the laser pulse train with the reference RF sine wave signal, the r.m.s. timing jitter calculated rrom the conventional phase noise spectra is 1.56ps. We then replace. RF sine wave signal with a 1GHz comb generator and the corresponding r.m.s timing jitter is reduced to 1.36ps, 1.26ps, 0.94ps, and 1.33ps when the 11th, 22th 33th, and 45th harmonic of the laser pulse train is used for intermixing. We design a circuit to detect the phase error signal in the time domain directly for computing the r.m.s timing jitter. The dorresponding r.m.s thming jitter is reduced to 524fs, 351fs, and 493fs when the 22th, 33th, and 45th harmonic of the laser pulse was used for intermixing.