被動鎖模鈦藍寶石雷射脈衝演變動力學之研究

Abstract

我們利用雙能階模型模擬飽和吸收染料在鎖模過程中扮演的角色, 計算出 在被動鎖模鈦藍寶石/DDI或IR140雷射中,從連續波噪音成長到單一脈衝的 動態演變過程. 實驗上, 我們利用時間閘技術量測在不同瞬間的暫態拍頻 信號, 藉以定性地估計鎖模的程度; 而定量的估計則由可以透過量測暫態 自相關軌跡的對比率(contrast ratio)獲得. 我們苜度成功觀察到雷射輸 出由連續波到部份鎖模, 到完全鎖模的整個演變過程. 實驗結果跟理論模 擬所預測的結果相當一致. The evolution from cw to partial mode-locking, to complete mode-locking in passively mode-locked Ti:sapphire/DDI and IR140 lasers has been determined by measuring the contrast ratios of transient autocorrelation traces at consecutive delay times using the time-gating technique. The corresponding transient RF spectra showing the growth of beat notes also agree with the above observation. The build-up of mode- lockedlses from cw noises can be simulated by a two- level- saturable-absorber model. The experimental results are in good agreement with the predictions of numerical simulation.