被動鎖模鈦藍寶石雷射時序紊亂度抑制之研究

Abstract

在本論文中，我們使用以光導開關為諧波混頻器的光電式鎖相迴路，進行被動鎖模鈦藍寶石雷射時序紊亂度抑制的研究。光導開關取代了傳統做法中的光偵測器以及微波混頻器，具有諸多優點。 我們發現以染料為飽和吸收體的被動鎖模鈦藍寶石雷射，在未迴授控制腔長的情況下，最佳的均方根時序紊亂度約為12.6ps。此值是利用頻譜分析儀解析度為10Hz時，量測100Hz到10Hz範圍的單邊帶相位雜訊頻譜計算得到的。利用光電式鎖相迴路抑制時序紊亂度，雷射的均方根時序紊亂度降至710fs(100-500Hz)，478fs(500-5kHz)，93fs(5kHz-10KHz)。 以量子井為飽和吸收體的被動鎖模欽藍寶石雷射，提供較小振幅及相位雜訊的光脈衝，在未迴授控制腔長的情況下，最佳的均方根時序紊亂度約為6.8ps。經過我們光電式鎖相迴路抑制時序紊亂度之後，均方根時序紊亂度降低了13dB，其值為290fs(100-500Hz，302fs(500-5kHz)，178fs(5kHz-10KHz)。

In this thesis, we demonstrate a new timing stabilization method based on an optoelectronic harmonic mixer (OEHM) in a phase-locked loop toreduce the timing jitter of passively mode-locked Ti: sapphire lasers. The OEHM replaces the photodiode and RF mixer combination in conventional approaches. The system becomes more flexible and allows the use of low-frequency electronics in the remainder of the phase-locked loop. In the home-made passively mode-locked Ti: Sapphire laser system that use dye as the saturable absorber, the optimal r.m.s. timing jitter of the freerunning laser is 12.6ps. This is calculated from single side-band phase noise spectrum measured from 100 Hz to 10 kHz at a resolution bandwidth of lOHz. 1The r.m.s. timing jitter of the stabilized laser is reduced to 710(100-500Hz), 478fs (500-5kHz), and 93fs (5kHz-IOKHz), espectively. Semiconductor quantum well as saturable absorbers in solid-state lasers can provide sufficiently stable amplitude-modulation to generate ultrafast optical pulses. Those characteristics efficiently reduces amplitude and phase noises of pulse trains. The optimal r.m.s. timing jitter of the free- running laser is 6.8ps, the r.m.s. timingjitter of the stabilized laser is reduced by a factor of about 13dB to 290fs (100-500Hz), 302fs (500-5kHz), and 178fs (5kHz-1OKHz), respectively.