控制光折變晶體中的調變不穩定

Control Modulation Instability in Photorefractive Crystals

蘇祐男(Su, Yonan)

指導教授 ： 李瑞光

國立清華大學/電機資訊學院/光電工程研究所/博士(2016年)

摘要

這篇論文包含三個部分:藉由不同同調程度的光來控制調變不穩定(MI)、藉由訊號光與背景光光強度比例來控制MI、藉由週期性調變外加偏壓控制MI能見度變化範圍。第一部分介紹外加偏壓與同調長度組成的相圖。可以觀察到MI1與MI2的兩種狀態與它們共存態、橫向不穩定、光汶流等狀態以外。兩不同週期與方向光調變不穩定條紋的共存行為可以藉由非等向性非線性係數來解釋。平面波與MI1、MI1與MI2轉換邊界可以被描繪在相圖上。第二個工作解釋MI在高光強的抑制行為: 折射率對光強度響應呈現飽和非線性。可以藉由不同訊號光與背景光比例來控制高對比度MI條紋落在訊號光的範圍。第三個工作施加不同頻率的調變偏壓來控制MI對比度震盪幅度。當非直覺MI對比度震盪頻率峰值被觀察到時，這方法有可能用來量測系統內部隨時間的微擾變化頻率。

關鍵字

調變不穩定 ； 自發性圖案生成 ； 飽和型非線性

並列摘要

This thesis covers three works: control Modulation instability (MI) by partial coherent light, control MI by background to signal beam intensity ratio, and control MI by periodically driving field. The first work introduces the phase diagram of biased voltage versus coherence length. MI1, MI1/MI2, MI2, Transverse Instability (TI), Optical turbulence (OT) states can be observed. MI1/MI2 mixed state can be explained by unisotropic nonlinear indexes and the transition boundaries of plain wave to MI1, MI1 to MI2 phases can be depicted on the phase diagram. The second work explains the MI suppression behavior in high intensity region which reveals saturable type refractive index to light intensity response. One can control the clear MI pattern range of signal light intensity via signal to background intensity ratio. The third work controls MI variation range using external periodic driving field with fast charge carriers dynamics assumed. MI with periodic driving could be a promising tool for measuring perturbation frequency when non-intuitive resonance peak is observed.

並列關鍵字

modulation instability ； spontaneous pattern formation ； saturable nonlinearity

參考文獻

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