Lateral mode engineering in diode lasers based on coupled ridges

Abstract

We present an experimental study on the edge-emitting lasers based on coupled ridges. The main idea of these structures is to ensure fundamental mode lasing in broadened multi-mode ridges by means of using a high-order mode filtering based on the resonant optical tunneling into a nearby passive stripe. For our experiments, we used a conventional InAs/InGaAs quantum dot (QD) laser wafer (λ∼1.28μm) and placed a 3 μm passive dielectric-covered ridge at the distance of 4 μm from 10 μm main active ridge. The devices demonstrated stable far-field patterns with suppressed first-order mode lasing and without any deterioration of the main laser parameters. However, side lobes in the far-field patterns indicated second-order mode traces attributed to the current spread from the main stripe, which increase the effective stripe width. We assume that optimization of the laser hafer and etching technique may lead to a pure lateral single-mode lasing in the coupled ridge devices.