短脈衝雷射時間紊亂度量測及控制之研究

Abstract

在本論文中，我們研究了兩種短脈衝雷射的時序紊亂度，就自組被動 鎖模鈦 藍寶石雷射而言，其時間紊亂度最佳值約為 11.2 ps（位 移頻率由 100Hz 至 10kHz）。我們並觀察到雷射共振腔內控 制頻寬用的狹縫寬度對其時間紊亂 度影響甚大。 我們也證實適當調整自饋增益開關半導體雷射回授光之延遲時間，可有效 地 將增益開關半導體雷射之時間紊亂度由 1.3 ps 降低至 1.1 ps（位移頻率由 100 Hz 至 10kHz），可調範圍約 25 ps，約為鎖模 雷射腔長可調整量的二至三個數量級。 在光電式鎖相迴路方面，藉 由鎖定高次諧波，我們可將其時間紊亂度由 68 ps降至 1.3 ps（基 頻鎖定）至 0.2 ps（五次諧頻鎖定）。若結合光電式高次諧波鎖相迴路 及自饋效應，增益開關半導體雷射之時間紊亂度可由 68 ps降至 0.9 ps （無自饋） 至 0.65 ps（自饋式）。 In this thesis, we have studied the timing jitter of optical pulses generated by a free-running mode-locked Ti:sapphire laser and a gain-switched semiconductor laser diode. In the home-made passively mode-locked Ti:Sapphire laser system, the optimal timing jitter of the free-running is 11.2ps.This is calculated from single side-band phase noise spectrum measured from 100 Hz to 10 kHz at a resolution bandwidth of 10Hz.We also observed that the timing jitter can be strongly affected by the wavelength- selecting slit inside the laser cavity. We also confirm that timing jitter of a self-seeding gain- switched laser diode can be further reduced from 1.3 ps down to 1.1ps by tuning the delay of the optical feedback in a range of 25ps.This is 2-3 order of magnitude larger than the corresponding value of a typical mode-locked laser.By using an optoelectronic phase lock loop,we observe that the timing jitter can be futher reduced from 68ps down to 1.3ps and 0.2ps when the laser is locked to the fundamental and 5th ordered harmonics.On the other hand,the timing jitter of the gain-switched semiconductor laser can be efficiently suppressed form 68ps down to 0.9ps （without feedback）and 0.65ps （with feedback） via the combination of optielectronic phase lock loop of the free-running laser at higher harmonics of a self-seeding gain-switched laser diode.