Optical Mode Modulation of AlGaInP Multi Quantum Well Laser Diodes

Abstract

We investigate the influence of passivation structure on the optical mode distribution and LI characteristics for the edge emitting AlGaInP-GaInP visible laser diode (LD). For traditional single-layer Si3N4 or SiO2 passivation designs, the modification of dielectric layer thickness can determinate the lateral near-field confinement and change the horizontal far-field (FF) divergence. By increasing the film thickness, the non-radiation absorption come from Au-Ti can be improved and it leads to a narrow FF divergence beam. As continue to increasing the thickness, thicker passivation provides a better confinement factor and then the far-field pattern turn to be wider. For LI characteristics, it is necessary to deposit a thick enough passivation to reduce metal absorption. However, it cause much thermal energy accumulated in the ridge waveguide and deteriorate the quantum efficiency as adopting a too thick dielectric layer. Finally, we demonstrate a high power AlGaInP-GaInP multi quantum wells (MQWs) LD adopted a high-reflectivity passivation to enhance the LI characteristics and keep a suitable far-field divergence angle simultaneously. Under the design of three-pair optical thin films, it cannot only avoid the metal absorption but also enhance emitting efficiency and heat dissipation by using a high reflective and good thermal conductive three-pair optical thin films, it cannot only avoid the metal absorption but also enhance emitting efficiency and heat dissipation by using a high reflective and good thermal conductive Al2O3/Ta2O5 multilayer. The measured room-temperature threshold current (I-th) and characteristic temperature (T-0) can be arrived 44.5mA and 104.2K at 16.4 degrees far-fielddivergence.