We report on the fabrication of InGaN-based multiple-quantum-well laser diodes (LDs) emitting at 420 nm. Structures with standard claddings (p-and n-AlGaN), asymmetric claddings (p-GaN and n-AlGaN), and AlGaN-free claddings were grown by metal organic vapor phase epitaxy on polar c-plane free-standing GaN substrates. Electrical and optical properties of each LD are presented. Thanks to an optimized design of the InGaN waveguide and active region, cw lasing of a completely AlGaN-free laser diode is demonstrated, with a threshold current density < 5 kA/cm(2) and a differential efficiency per facet of similar to 0.4 W/A without high-reflection coatings. (c) 2010 The Japan Society of Applied Physics