雷射系統動力學研究 從混亂無序到類似周期性弛張振盪

Abstract

本論文研究主要是藉由實驗觀察發現，由平行平面光學共振腔結構在一般的示波器(500MHz)觀察下，其輸出的時域(time domain)信號，是連續波 (continuous wave：CW)輸出信號，是與時間軸平行的橫線輸出。但在高速示波器(40GHz)的觀察下，時域信號則是一個混亂無序不平整的輸出信號，也就是說，CW光學共振腔中仍然有動態(dynamic)現象發生。進一步實驗觀察在不同情況下動態行為的變化情形：這些上下波動(fluctuation)不平整的信號，可藉由使用緊密式耦合共振腔(closed coupled cavity)的結構，改變不同的光學元件(如楔形雷射晶體(wedge-cut laser crystal)及楔形輸出耦合鏡(wedge-cut output coupler))，得到一個整齊而有週期性的自我脈衝(self-pulsation)的輸出信號，近似於鎖膜(mode-locked)輸出信號。因此，緊密式耦合光學共振腔，可提供了一個微小簡縮腔(compact resonator)結構，也很容易的調整腔長並獲得不同的信號重複率。由於高重複率的雷射輸出信號、腔長變短、結構簡單，很有潛力的廣泛應用在產業界中；如運用在通訊系統等方面。

The purpose of this study is by experiments and observations to discover the output signal, it is produced by the plane-parallel resonator. The output time domain signal is continuous wave (CW) observed under the general oscilloscope (resolution 500MHz). The CW signal is parallel with X-axis (time axis). But when we observed the signal under the high speed oscilloscope (resolution 40GHz), there were still dynamic phenomena in the optical resonator. By means of changed the different factors, for examples, changed wedge-cut laser crystal and wedge-cut output coupler, we can clearly observe dynamic variations and fluctuations in different situations. Therefore, to advance experiments and discover that using the closed coupled cavity is to form the optical resonator. It may obtain not only a uniform periodic self pulsations signal but also a near perfect mode-locking output pattern. Besides the cavity can also offer a compact size resonator, easily modulate the length of the optical cavity, and obtain different repeating frequency。 Due to the higher laser output repeating frequencies、 sinusoidal-like pattern、 shortened the cavity and simple resonator structure characteristics, it can extremely get promising applications in industrial fields, such as applications in telecommunication systems.