Control of slow axis mode behaviour with waveguide phase structures in semiconductor broad-area lasers

One of the most common methods to increase the output power of semiconductor waveguide lasers is broadening the stripe width of the active region. However, this results in higher order transverse modes to be amplified which impairs the beam quality and increases the beam divergence. By integrating optical elements into the cavity, it is possible to control the amplitude shape and the number of modes which are amplified in the laser. This paper reports on aspects to integrate phase and amplitude modifying microstructures into a semiconductor waveguide resonator by adding an additional lithographic step to the fabrication process of broad area laser diodes. The latest experimental results of such structured InGaAIP broad area lasers revealed a significant improvement of the beam quality even at a high operation current. Hence, the expansion of the stripe width of the amplifying region without degrading the beam quality is possible. The demonstrated power-current characteristics of structured laser diodes exhibit a low threshold current and a high efficiency.