Theoretical Design Of Er-Doped And Yb-Er Co-Doped Al₂O₃ Waveguide Amplifier On SiO₂/Si Substrate

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.