【作者】 李淑凤；

【导师】 宋昌烈；

【作者基本信息】 大连理工大学 ， 光学工程， 2004， 博士

【摘要】 本文对SiO2/Si基掺Er及Yb-Er共掺Al2O3光波导放大器(EDAWA和YEDAWA)进行了系统的理论分析、数值模拟和实验研究。考虑了合作上转换、交叉弛豫、激发态吸收等上转换机制,分别建立了针对三种泵浦波长的Er3+跃迁的速率方程。分析了掺ErAl2O3样品的1. 53μm荧光强度与反转粒子数随泵浦波长、泵浦强度及掺Er浓度的关系。结果表明0. 98 μm波长泵浦时,荧光强,反转度高。三种泵浦波长按泵浦效率排序是0. 98 μm、1. 48 μm、0. 82 μm,我们选择0. 98μm作为掺ErAl2O3波导放大器的最佳泵浦波长。通过分析镱铒离子的能量转换机制及各种上转换效应,建立了一套目前考虑最全面的0. 98μm泵浦Yb-Er共掺系统的速率方程。利用Yb-Er共掺Al2O3薄膜的相关数据进行模拟计算,结果显示Yb的掺杂可提高Er3+的荧光强度和反转粒子数,并使实现粒子数反转的阈值泵浦强度最大可降低一个数量级。通常的掺铒浓度下,确定优化的镱铒浓度比为1-2. 5。利用Ansys软件中高频电磁模块,建立了二维波导的有限元模型,成功地求解了开放介质波导中场的传输模式和各模式的场分布。得到了3μm宽矩形截面脊波导的色散曲线,确定了信号光单模传输的最佳脊高为0. 8 μm。采用阶跃折射率光纤的Bessel场激发波导模式,得到各模式的激发系数及信号光和泵浦光的归一化光强。详细分析了光纤芯径和偏移对光纤-波导耦合效率的影响。利用速率方程、有限元场分布、传输方程,考虑正反方向的自发辐射噪声的影响,采用Runge-Kutta迭代技术求解了EDAWA和YEDAWA增益。该综合理论模型的计算结果表明YEDAWA的泵浦效率高于EDAWA,并分析了两种放大器的偏振特性,噪声特性以及耦合对增益的影响。这些结果均是国内外未见报道的。本模拟计算中建立的更为先进的参数优化方案,实现了放大器掺杂浓度、泵浦功率、波导长度和增益的同步优化,得到最佳长度下的最大增益,绘制出具有实用和指导价值的优化设计曲线。分析比较了梯形、矩形和倒梯形截面脊波导的模场、对场功率的约束以及放大器的增益,确定了最佳波导结构。这项研究结果可为波导放大器的刻蚀提供理论指导。实验研究了YEDAWA的增益特性,70mW泵浦下获得了8. 44dB的净增益,阈值泵浦功率18mW,并与理论结果作了对比,二者符合较好。更多还原

【Abstract】 The characteristics of Er doped and Yb- Er co-doped Al2O3 waveguide amplifiers based on SiO2/Si are investigated by theoretical analysis, numerical simulation and experimental research.Considering cooperative up-conversion, cross-relaxation and excited state absorption, rate equations of Er3+ energy level transitions are founded for three kinds of pumping wavelength. 1.53μm photoluminescence intensity and population inversion are analyzed as the function of the pump wavelength, pump intensity and Er concentration. 0.98μm for pumping efficiency is in the first rank, next is 1.48μm, and last is 0.82μm.Rate equations of Yb-Er co-doped system are founded through analyzing Yb-Er energy transfer and other up-conversion mechanizations. Using the latest parameter’s data of Yb-Er co-doped Al2O3 films, the results show that Yb3+ co-doping can increase photoluminescence intensity and population inversion and lower the threshold power. Under the common Er concentration optimum Yb/Er concentration ratio is 1~2.5.By high frequency electromagnetism module of Ansys software, two-dimension waveguide finite element model is founded. Guiding mode propagation constant and the field distribution are computed successfully, dispersive curve is gained for rectangular rib waveguide. Film thickness 1μm, rib wide 3μm and rib height 0.8μm are determined for assuring single-mode operation at signal wavelength.Normalized intensity distributions of signal and pump, as well as mode excitation fractions, are obtained excited by the field of step refractive index fiber. Influences of fiber core radium and offset on the coupled efficiency are discussed in detail.Propagation equations are combined with rate equation, finite element field distribution, Runge-Kutta multi-step integration, at the same time, forward and backward direction amplified spontaneous emission are taken into account. The gains of Amplifiers are calculated. The results show that the efficiency of YEDAWA is higher than that of EDAWA. The polarization and noise characteristic of amplifier are analyzed. The dependence of the gain on Er concentration, pump power and amplifier length are shown. Optimum design curve is obtained, which is more reasonable and accord with design requirements more.The gain and confinements of electromagnetic field in the active region are compared for three different geometry structure waveguide amplifiers (rectangle, trapeze, upside down trapeze), which can provide theoretical guidance for waveguide etch and amplifier design.The gain characteristic of YEDAWA is investigated in experiment. The net gain of 8.44dB is obtained at 70mW pump power. Threshold pump power is 18mW, which is close to the calculation results.更多还原