A vertical slab waveguide design for an all-optical switch based on intersubband transitions in molecular beam epitaxy (MBE)-grown coupled double InGaAs/AlAsSb quantum well (QW) structures is presented. We propose a waveguide with two surrounding high refractive index InGaAsP guiding layers, which confine the optical mode in the low refractive index QW region and thus enable light guiding with low contrast InP cladding layers. We investigate the proposed concept by means of 1D simulations of several waveguide configurations. We confirm its validity by fabricating deeply etched waveguiding structures using either wet- or dry-etching technologies. Optical losses as low as 13.5 dB cm(-1) and 12.8 dB cm(-1) were measured for TM- and TE-polarized light, respectively.