A low-threshold second-harmonic generation horizontal cavity surface emitting laser (SHG-HCSEL) operating at 0.49 micrometers under electrical pumping is proposed and theoretical design considerations are presented. The strained InGaAs quantum well (QW) laser, implemented on a nearly optimally oriented (311)B-GaAs substrate, incorporates a reduced Al-content, quasi-phase matched (QPM) single guiding GaAs layer (SGL) structure, a novel double-tapered horizontal waveguide with high reflection-coated cleaved facets, and a metallization- free emission window at the center of the device. The horizontal geometry serves to increase the ratio of fundamental power density within the SHG-region to that at the facets, thereby increasing the laser optical power at the onset of catastrophic optical damage (COD) at the facets. Simulations indicate that surface blue emission (on the order of 14 W/cm2 peak, corresponding to 50 (mu) W for a 10 micrometers X 100 micrometers emission window) can be obtained from a compact device, with a moderate taper angle of 3 degree(s), operating well below the COD limit. The model also shows that a SGL thickness of 175 nm corresponds with the second QPM-SHG efficiency peak which coincides with peak optical confinement in the QW. Finally, AlGaAs cladding thickness of 113 nm is found to be the optimum etch condition beneath the SHG emission window.