(AlGaIn)(AsSb) quantum well diode lasers with improved beam quality

Type-I diode lasers based on the (AIGaIn)(AsSb) material family are ideally suited to cover the 2-3 µm wavelength range. In this paper recent progress in terms of output power, beam quality and wavelength tunability is reported, achieved for broad-area and tapered single emitters as well as for linear broad-area laser arrays. Special attention has been paid to the reduction of the fast axis far-field beam divergence, employing improved vertical waveguide laser designs. Furthermore, tapered diode lasers have been developed in order to increase the slow axis beam quality at high output powers. An improved beam quality is of particular importance as many applications, including coupling the laser output into an optical fiber or into an external resonator, require diode lasers with a low beam divergence and a high brightness rather than sheer output power.