Design and Experimental Characterization of an Erbium Doped GaN Waveguide

Abstract

ABSTRACT The goal of this research was to develop an optical amplifier based on Erbium doped GaN waveguides, which can be used in the next-generation of planar integrated optic circuits. This thesis started from the basic concepts of fiber optic communication systems, attenuation of optical signals, principles of optical amplifiers and planar optical waveguides. We focused on the principles and applications of Erbium doped fiber amplifiers (EDFA) and the physical properties of Er: GaN waveguides. This thesis reports the characteristics of an erbium-doped GaN semiconductor waveguide amplifier grown by metal-organic chemical vapor deposition (MOCVD). We demonstrated that both 980 and 1480 nm optical pumping were efficient to create population inversion between the 4I13/2 and 4I15/2 energy levels. The carrier lifetime in the 4I13/2 energy band was measured to be approximately 1.5 ms in room temperature, which is slightly shorter than that in erbium-doped silica due to the interaction between the erbium ions and the semiconductor lattice structure. But it is significantly longer than the carrier lifetime in a typical semiconductor optical amplifier which is in the nanosecond regime. The emission cross section was obtained with the Füchtbauer-Ladenburg (FL) equation based on the measured spontaneous emission and the radiative carrier lifetime. The absorption cross section was derived from the emission cross section through their relation provided from the McCumber's theory. The conversion efficiency from a 1480nm pump to 1537nm emission was measured, which reasonably agreed with the calculation based on the emission and absorption cross section.