大面積雷射光束線叢的研究

Abstract

光束線叢現象在大面積半導體雷射中是一個十分普遍的現象，它的形成 主要由兩個本質性的機制所導致，它們分別是：載子感應系數改變與光強 度感應系數改變。在這篇論文中，我們在理論上探討這兩種機制對半導體 雷射的光束線叢形成的影晌。我們首先推導完整的理論糢型，並且用兩種 不同的數值方法去計算它，這兩種數值方法分別是二維光束傳播法和一維 非線性特徵方程式法。計算結果顯示當在雷射共振腔內的載子濃度和電場 強度越大，則需要越小的導電寬度來避免光束線叢現象的發生；而不對稱 的雷射結構更會進一步降低雷射的臨界導電寬度的大小。在論文的最後， 研究結果更顯示，這兩種機制是可以互相平衡抵消的，據此，我們提出了 一個沒有光束線叢現象的大導電寬度(50um)的半導體雷射結構。 Filamentation commonly occurs in broad area semiconductor laser due to two intinsic mechanisms: carrier-induced index change and intensity-induced index change. In this thesis, we investigate the effects of thesetwo mechanisms to the formation of filaments in semiconductor lasers theoretically. The theoretical model is derived thoroughly and two numericalmethods are used to calculate it, and they are 2-D Beam Propagation Method and 1-D Nonlinear Eigen-Equation method. The results show that when the magnitude of the carrier density and electric field intensity existing inside the laser cavity are higher, smaller stripe width is needed for the lasers to avoid occurring filamentation. Furthermore, unsymmetry laserstructure will be lower down the critical stripe width of the lasers. Finally, our results suggest the possibility of obtaining large stripe width semiconductor laser diodes (50um) without filamentation by using compensation between these two mechanisms.