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標題: Evolutions of the Modulation Instability
作者: 鄭建宗
關鍵字: 基礎研究
Modulation Instability
Pattern Formation
Nonlinear optics
摘要: The modulation instability was widely discussed in the fluids in the 1960s. Thenon-linear optical crystal can directly corresponds to weakly correlated phenomenon indiverse nonlinear many-body systems, including cooled atomic gases at slightly higherBose-Einstein condensation critical temperatures and semiconductors at the vicinity ofthe quantum Hall regime. Due to the nonlinear optics similar to their mechanisms, thetopics were coming back and were studied widely in the recent decades. The researchexcept for the dynamic property of the modulation instability, the dynamic conduct ofthe modulation instability in noninstantaneous media, the stability of order structure,and the spontaneous property of the modulation instability, lately we found that in themodulation instability, the stripe filaments transform into dot filaments, not the causeof anisotropy of the crystal, but the cause of the transverse instability. In other words,in the system of isotropy, taking cooled atomic gases at Bose-Einstein condensationtemperatures as an example, should emerge the same phenomena. This improvementhelps a lot not only to figure out the development of the modulation instability, butalso to realize the forming conditions and how to predict the final state; or to deducethe initial conditions and processes.
「調變不穩定性」(Modulation Instability, MI)早在1960 年代對研究流體時,就被廣泛探討的現象,最近發現在非線性光學晶體所出現的「調變不穩定」現象可以直接對應到微弱作用(Weakly Correlated)的多體系統中的現象,包括冷原子氣(Cooled AtomicGas),在溫度略高於波色-愛因斯坦凝聚態(Bose-Einstein Condensation, BEC)臨界溫度時的行為,以及半導體在接近量子霍爾效應區域時發生的現象,這些現象的作用機制與非線性光學類似,因此光的「調變不穩定性」在近十年重新被廣泛研究。我們的研究除了探討「光調變不穩定性」的動態特性、非立即性反應材料中的光調變不穩定的動態行為、有序結構的穩定性,以及自發性MI 特性外,我們最近發現「調變不穩定性」條狀圖形轉變為點狀,並非是晶體的各向異性所造成的,而是另一方向的不穩定,也就是橫向不穩定性(Transverse Instability, TI)出現所造成的,換言之在各向同性的系統中,例如冷原子氣體達到BEC 狀態等,應該也會出現相同現象,這個進展對於瞭解 MI形成的演化過程,有很大的幫助,同時也有助於瞭解形成的條件,以及如何預測最後狀態,或反推初始條件及過程。
其他識別: NSC99-2112-M005-006-MY3
Appears in Collections:物理學系所



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