Reduction of aspect ratio in 650 nm-band self-sustained-pulsing lasers with saturable-absorbing layer

650 nm-band self-pulsing lasers which exhibit an extremely low laser beam profile aspect ratio (2.6) and a small astigmatism (2 µm) were successfully demonstrated by optimizing the design of the layer structure. Low-noise self-pulsing lasers have been developed as a light source for optical disc systems. In the case of mounting the lasers on optical systems, a low aspect ratio and a small astigmatism are required in order to realize high optical coupling efficiency and good optical focusing characteristics. In this paper, we report a reduction of the aspect ratio while maintaining a small astigmatism in self-pulsing AlGaInP lasers with a saturable absorbing (SA) layer by optimizing the optical confinement and compressive strain in the SA layer. Simultaneously, a very low intensity noise characteristic up to 50° C was confirmed by stable self-sustained pulsation characteristics.