High power AlGaInP laser diodes (LDs) and bars emitting at about 685 nm have been fabricated. The epitaxial structures, including the AlInP cladding layer, asymmetric waveguide and single compressive-strained quantum well, were designed to optimize the thermal performance. The transparent window structure formed by Zn diffusion was employed to increase the output power of AlGaInP LDs. A maximum power of 4.9 W was realized for the single emitter LDs without catastrophic optical damage. Using micro-channel heat sinks, an array stacked with six 1-cm bars showed an output power of more than 300 W with 40% conversion efficiency.