Analysis of Optical Waveguide Mode in Closely-Stacked InAs/GaAs Quantum Dot Semiconductor Optical Amplifiers

Abstract

We performed modal analysis for 40-stacked InAs/GaAs quantum dot semiconductor optical amplifiers (QDSOAs) as a function of the waveguide width using an equivalent refractive index technique. QDSOAs with 5- and 11-μm-waveguide widths show multi-mode operations. The theoretical simulation reproduced well the experimental electroluminescence spectrum and unveiled that the output signals comprise several transverse modes. Besides, we confirmed a waveguide width less than 1.28 μm is essential to realize single-mode QDSOAs. The modal gain spectra were analyzed by using the Hakki-Paoli method. Multi peaks arisen from the multi-mode operation were also observed in the gain spectrum, suggesting precise control of the transverse mode is important for a practical realization of the single-mode device.