Experimental characterization and numerical modelling of an AlGaAs oscillator broad area double pass amplifier system

This paper reports on an experimental characterization and numerical analysis of the performance of a special AlGaAs master oscillator power amplifier (MOPA) system. This MOPA consists of a single stripe diode laser and a broad area double-pass amplifier. With an input of 76 mW, the amplifier generates 780 mW of 810 nm radiation in an almost diffraction limited beam (M-2 1.1). The detailed experimental characterization includes the measurement of the output power as a function of the optical and electrical input power as well as the measurement of the dependence of the small signal gain, the saturation power and the power of the amplified spontaneous emission (ASE) on the amplifier current. The numerical analysis is based on a two-dimensional model which considers the spatial propagation and amplification of the input beam in the amplifier's active layer and the gain competition between ASE and the amplified input radiation. The numerical simulation provides values for parameters measured in the experiment (such as the saturation power or the small signal gain) and the power distribution in the amplifying layer. The good agreement between the experimental and numerical results indicates that the phenomenological, steady-state description of the amplification process should be well suited for a simple and rapid analysis of basic properties of high-power diode laser amplifiers.