量子點雷射受激態及溫度效應之模擬與分析

Influence of excited states and temperature effects on quantum-dot laser properties–modeling and analysis

陳羨尊(Hsien-Tsun Chen)

指導教授 ： 毛明華

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.02277

摘要

在本文中，我們透過數值分析的方法來解雷射的變率方程式，在量子點雷射理論模型中，除了引進非均勻寬化效應(inhomogeneous broadening effect)、均勻寬化效應(homogeneous broadening effect)、將量子點依其大小分群外，並加入了受激態的影響及溫度效應等因素。
且在室溫下，測試不同條件量子點所製成之雷射元件特性，包括其形狀大小及成長之均勻度，並改變了雷射共振腔的長度，觀察臨界電流及發光波長隨損耗的變化，有著平滑或是階梯狀等不同情形，此可幫助預測雷射由基態放光轉至受激態放光的時機，以決定雷射共振腔長度之最佳設計。
再者，個別探討三種溫度因素如何影響雷射之臨界電流(threshold current)，其分別為均勻寬化效應、載子捕獲時間(carrier capture time)及載子熱逃脫效應(thermal escape)，借以釐清負特徵溫度現象之原由，發現除可單獨由載子在量子點中之熱平衡分布而造成，亦可由載子捕捉時間和均勻寬化效應間彼此消長而生。

關鍵字

量子點 ； 模擬 ； 雷射 ； 受激態

並列摘要

A set of coupled rate equations is applied to analyze quantum-dot laser properties. Except for the inhomogeneous broadening effect due to the quantum-dot size fluctuation, and the homogeneous broadening effect, the influences of excited states and temperature effects are also taken into account.
At room temperature, the threshold current density and lasing wavelength as a function of loss are calculated. The conditions for a smooth or step-like change in the lasing wavelength are described and are provided for the optimum design of laser cavity lengths. These would help us to avoid lasing via the excited-state due to short laser cavities.
Furthermore, three different mechanisms of temperature effects on quantum-dot laser threshold, i.e. homogeneous broadening effect, carrier capture time and carrier thermal escape from quantum dots, are investigated in details to show their individual influence on laser threshold behavior. The unique negative characteristic temperature phenomenon of quantum-dot lasers is therefore clarified. Not only the thermal equilibrium distribution of carriers among quantum dots, but also the interplay of carrier capture time and homogeneous broadening will cause the negative characteristic temperature phenomenon.

並列關鍵字

laser ； excited state ； quantum dot ； modeling

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