It is well-known that the optical properties of semiconductor nanostructures are so sensitive to alteration of confinement while the nanostructure's morphology often determines the confinement. Accordingly existence of a bulge on the wire surface will affect the specifications of the nanowire. However, bulge existence effects are significant for ultrafine nanowires and negligible for wires with large radius. In the present work we consider a GaAs ultrafine nanowire with a bulge on the middle of wire axis. The linear, third-order nonlinear and total absorption coefficient and refractive index changes variations are investigated as functions of bulge and nanowire radius. Also the effects of bulge and wire radius on saturation are studied. It has been found that increment in wire (bulge) radius leads to a red shift (blue shift) in absorption coefficient and refractive index changes curves. Additionally, alteration of wire and bulge radii, changes the corresponding incident photon intensity that saturation occurs at it. (C) 2015 Elsevier Ltd. All rights reserved.