Beam Propagation Model of Tapered Amplifiers including Non-Linear Gain and Carrier Diffusion

Abstract

Recent interest in high-power single-mode diode lasers has led to the evaluation of a variety of semiconductor amplifier geometries [1], integrated master oscillator power amplifier (MOPA), designs and flared oscillator devices. Flared amplifiers and oscillators have been found to be less sensitive to filamentation effects than broad area devices, although filamentation still ultimately limits the performance of such devices [2]. Using a FD-BPM model we investigate the performance to be expected from various flared laser structures in terms of both output power and beam quality. We clarify the influence of such material parameters as the number of quantum wells, the differential quantum efficiency and the linewidth enhancement factor on the output beam profile of the amplifier. We point out the influence of the linewidth enhancement factor showing that a reduction of this factor improves the output beam quality, the resistance to inhomogeneous injection, and the output farfield. Furthermore, a simulation of a 2D integrated elliptical lens is presented, showing the possibility of ‘on chip’ correction of the astigmatism for low α-factor structures. Such a lens would spare the use of an external cylindrical lens for collimation of the output signal.