Effect of the Y-junction output coupler on the lasing threshold of semiconductor ring lasers

Abstract

We report the first measurements of the effect of a Y-junction output coupler on the continuous-wave (cw) lasing threshold of rib-waveguide semiconductor ring lasers. We show that the Y-junction induced loss in this type of ring diode laser depends on the ring radius (r), and increases the lasing threshold current density substantially for devices with r<200 μm. For our devices with radii of 50–100 μm, the Y-junction loss term is shown to be the dominant factor affecting the cw lasing threshold. We also report the first measurements of the dependence of the cw lasing threshold on the width (w) of the Y-junction output coupler, and show that the threshold current density increases linearly for 0≤w≤9 μm.