High brightness tapered laser diodes with different resonator geometries were fabricated and analysed. The devices consist of an index-guided straight section and a gain-guided tapered section. Lasers with a total length L = 2 and 4 mm and different length of the ridge waveguide L-RW (500 mum less than or equal to L-RW less than or equal to 1250 mum for L = 2 mm and 500 mum less than or equal to L-RW less than or equal to 2000 mum for L = 4 mm) were processed to study the influence of the straight section on the spatial mode filtering. The power-voltage-current-characteristics, the beam waist, the far field, and the beam propagation factor M-2 were measured. From the experiments, it can be stated that the lasers with a small L-RW reach higher output powers compared to those with larger L-RW. Concerning the beam quality the length L-RW should exceed a minimal value to guarantee efficient spatial mode filtering. Devices optimised concerning maximum output power and excellent beam quality reach a beam propagation factor smaller than 2.1 at an output power P = 2 W. References: 20
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