A novel waveguide structure for AlGaInP visible separate confinement heterostructure quantum well laser with inserting low-refractive-index AlAs layers is theoretically investigated using the transfer matrix method. By using this structure, we can significantly improve the transverse beam divergence and reduce the threshold current. Otherwise, the inserting AlAs can also be used as a wet etching automatic stopped layer. Because the thermal resistance of AlAs is smaller than that of AlGaInP, the thermal characteristics of this novel structure are also better than the conventional AlGaInP visible lasers. With the inserting AlAs layers, the transverse beam divergence and the threshold current density can be reduced from38°to8.84°and 787 to 666.8 A/cm2, respectively. ©1997 American Institute of Physics.