Study of Temperature Characteristics of 1.3μm Strain-Layer Multiple Quantum Well Lasers

Abstract

<p>This thesis presents a theoretical and experimental study of the temperature characteristics of 1.3μm strained layer multiple quantum well (MQW) lasers over a wide temperature range. A number of achievements have been made toward understanding the temperature sensitivity of the performance of the lasers.</p> <p>Under assumptions that the deterioration of optical gain with temperature dominates the temperature sensitivity of the laser performance and that the differential gain coefficient decreases linearly with temperature, two formulae, which include a maximum operating temperature, were derived to describe the threshold current, Ith, and the external quantum efficiency, ηd, as functions of temperature. The formulae produce a very good fit to the experimental data that were extracted from the shortpulse L-I characteristics of 1.3μm 0.7% compressive strained layer MQW lasers containing varying number of wells. The maximum operating temperatures obtained from fitting the formulae to Ith vs. T and ηd vs. T data are consistent with each other, which experimentally supports the theory and the underlying assumptions. Based on the same assumptions, the conventional method of determining the internal quantum efficiency and internal loss from a set of lasers with different length was scrutinized. It was concluded that the internal quantum efficiency is a function of temperature, even if the true internal quantum efficiency is independent of temperature, and that the internal loss is a sublinear function of temperature around room temperature, as available experimental results show. The experimental results from 1.3μm ten 0.7% compressively strained wells lasers with varying cavity length support the theoretical conclusions.</p> <p>The experimental observation of the far-field patterns for 1.3μm 1.2% tensile strained layer MQW lasers containing 3 wells with varying ridge width over a wide temperature range indicated that the injected carriers exert little effect on the refractive index, and that the change in the far field distribution with temperature is the result of spatial hole-burning.</p> <p>The final part of this thesis presents a technique to determine the temperature rise of the lasers during CW operation, which was then used to calculate the thermal impedances of different ridge width lasers. It was concluded that a wider ridge laser has a smaller thermal impedance and a lower available CW maximum operating temperature.</p>